@article{9714021,

title = {Source identification of propagating waves inside a network},

author = {Franck Plouraboue and Pierre Uszes and Romain Guibert},

doi = {10.1109/TNSE.2022.3144647},

issn = {2327-4697},

year  = {2022},

date = {2022-02-14},

journal = {IEEE Transactions on Network Science and Engineering},

pages = {1-1},

abstract = {The localization of short events arising within a network subsequently leading to wave propagation into it, is of interest in many applications. This work extend [1] which demonstrated the identifiability of a source from two detectors in a N nodes graph. We show that, rather than a source, a boundary condition identification is also possible and demonstrate a generalyzed unicity result. Furthermore, we extend the identification algorithm proposed in [1] to an arbitrary number of sensors, and estimate its complexity which depends on sensors number $N_s$ and time dicretisation $N_t$. Increasing detectors number increases source identification robustness to noise up to a cut-off number being a small raction of N. This cutt-off detector density for efficiency in noise reduction is of practical significance. We also analyze and discuss the method sensitivity to total recording time $T_e$, sampling frequency, and signal to noise ratio. Finally we propose a pre-sectorisation to improve the systematic exploration algorithm proposed in [1] and we show a $O(N)$ drop in complexity leading to a $O(N^3)$ cost for the source identification. Several tests of the method on model and real graphs confirm and support the presented results.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Lemetayer_2022,

title = {Multi-inception patterns of emitter array/collector systems in DC corona discharge},

author = {Lemetayer Julien and Marion Corentin and Fabre David and Plouraboué Franck},

url = {https://iopscience.iop.org/article/10.1088/1361-6463/ac4e35},

doi = {10.1088/1361-6463/ac4e35},

year  = {2022},

date = {2022-01-01},

urldate = {2022-01-01},

journal = {Journal of Physics D: Applied Physics},

volume = {55},

abstract = {Multiple emitters systems have been previously used so as to increase charge density in the drift region, many times without producing sensible increment neither in total current nor ionic wind. This contribution focuses on analyzing the detailed physics behind this failure, that is named 'multiple emitters un-scalability'. It is established that multiple emitters un-scalability is related to the inability of multiple corona discharge inceptions when increasing the emitter number and/or density. This confirms recent findings that corona discharge inception is shielded by electro-static interactions between emitters. This contribution demonstrates that this shielding can be balanced by emitter/collector electrostatic interactions depending on the considered configuration. For sufficiently close collector-emitter distances, ignition starts at the array center, whereas, on the contrary, when the collector is distant, the ignition not only starts at the array's periphery but might also be limited there. It is also demonstrated that emitter/emitter electrostatic interactions can be balanced by emitter/collector ones, depending of their chosen configuration. This lead to a variety of multi-inception patterns, the condition of which are analyzed. Intermediate configurations for which the collector is neither sufficiently close nor distant from the emitter array center provide a variety of multi-inception patterns that are hereby analyzed. Combining finite element computations of multi-inception drift-diffusion modeling with experimental measurements, provides a coherent picture explaining why multiple emitters sources systems do not lead to full ignition, and also exhibit conditions for which it does, leading to multiple emitters scalable systems.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao26598,

title = {Image-based effective medium approximation for fast permeability evaluation of porous media core samples},

author = {Jacques Franc and Romain Guibert and Pierre Horgue and Gérald Debenest and Franck Plouraboué},

url = {https://oatao.univ-toulouse.fr/26598/},

doi = {10.1007/s10596-020-09991-0},

year  = {2021},

date = {2021-08-01},

journal = {Computational Geosciences},

volume = {25},

pages = {105--117},

publisher = {Springer Verlag (Germany)},

abstract = {An image-based effective medium approximation (EMA) is developed so as to permit very fast transport properties evaluations of 3D porous media. From an image-based porous network (IBPN) built upon digital image processing of 3D binary images, we focus on throat?s local geometrical properties at the pore scale, for being the most sensible structural units which build up the local pressure. This approach is a 3D image?based extension of the critical point approach proposed in 2D fractures. We show, from analyzing various core rock samples available in the literature, that the asymptotic assumptions associated with the preeminence of critical points in throats are indeed geometrically relevant. We then describe how the image-based EMA evaluated from the conductances computed from the discrete IBPN can be reliably evaluated. The proposed method is evaluated upon the estimation of core sample permeability from binarized image obtained using X-ray tomography. Since it combines digital image treatments with statistical data post-processing without the need of computational fluid dynamics (CFD) computation, it is extremely cost efficient. The results are compared with a micro-scale Stokes flow computation in various rock samples. The sensitivity to the pore discretization also is discussed and illustrated.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao27560,

title = {Numerical study of ElectroAeroDynamic force and current resulting from ionic wind in emitter/collector systems},

author = {Sergiu Coseru and David Fabre and Franck Plouraboué},

url = {https://oatao.univ-toulouse.fr/27560/},

doi = {10.1063/5.0041061},

year  = {2021},

date = {2021-03-01},

journal = {Journal of Applied Physics},

volume = {129},

number = {10},

pages = {103304},

publisher = {American Institute of Physics},

abstract = {ElectroAeroDynamic (EAD) propulsion has recently shown a growing interest with distinct propulsive capabilities and specific advantages. These experimental observations are, therefore, driving interest for numerical predictions of their propulsive capabilities. Keeping with a drift region description associated with the Kaptzov approximation of the corona discharge region effect, we evaluate the detailed contributions of EAD forces from electro-drift effects computation only. We propose a new regularization procedure for the numerical formulation of the electro-drift problem, allowing the convergence of the resulting iterative procedure (here a Newton method) over very large domains, using iteratively adapted meshes in high gradient regions. Our predictions show a good comparison with many experimental configurations, for both the current/intensity and the propulsive force. In some cases, we identify the air drag and the Kaptzov approximation to explain discrepancies with experimental measurements. Finally,},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao27422,

title = {A new model for the emergence of blood capillary networks},

author = {Pedro Aceves-Sanchez and Benjamin Aymard and Diane Peurichard and Pol Kennel and Anne Lorsignol and Franck Plouraboué and Louis Casteilla and Pierre Degond},

url = {https://oatao.univ-toulouse.fr/27422/},

doi = {10.3934/nhm.2021001},

year  = {2021},

date = {2021-03-01},

journal = {Networks & Heterogeneous Media},

volume = {16},

number = {1},

pages = {91--138},

publisher = {American Institute of Sciences Mathematical},

abstract = {We propose a new model for the emergence of blood capillary networks. We assimilate the tissue and extra cellular matrix as a porous medium, using Darcy's law for describing both blood and interstitial fluid flows. Oxygen obeys a convection-diffusion-reaction equation describing advection by the blood, diffusion and consumption by the tissue. Discrete agents named capillary elements and modelling groups of endothelial cells are created or deleted according to different rules involving the oxygen concentration gradient, the blood velocity, the sheer stress or the capillary element density. Once created, a capillary element locally enhances the hydraulic conductivity matrix, contributing to a local increase of the blood velocity and oxygen flow. No connectivity between the capillary elements is imposed. The coupling between blood, oxygen flow and capillary elements provides a positive feedback mechanism which triggers the emergence of a network of channels of high hydraulic conductivity which we identify as new blood capillaries. We provide two different, biologically relevant geometrical settings and numerically analyze the influence of each of the capillary creation mechanism in detail. All mechanisms seem to concur towards a harmonious network but the most important ones are those involving oxygen gradient and sheer stress. A detailed discussion of this model with respect to the literature and its potential future developments concludes the paper.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{MONROLIN2021110517,

title = {Multi-scale two-domain numerical modeling of stationary positive DC corona discharge/drift-region coupling},

author = {Nicolas Monrolin and Franck Plouraboué},

url = {https://www.sciencedirect.com/science/article/pii/S0021999121004125},

doi = {https://doi.org/10.1016/j.jcp.2021.110517},

issn = {0021-9991},

year  = {2021},

date = {2021-01-01},

journal = {Journal of Computational Physics},

volume = {443},

pages = {110517},

abstract = {Corona discharge modeling mostly relies on two, mostly distinct, approaches: high-fidelity, numerically challenging, unsteady simulations having high-computational cost or low-fidelity simulations based on empirical assumptions such as constant electric field at the emitter electrode. For the purpose of steady discharge current predictions, high-fidelity models are very costly to use whilst empirical models have limited range of validity owing the subtle use of tuned parameters. We propose an intermediate approach: an asymptotic multi-scale/two-domain numerical modeling based upon generalizing previous asymptotic axi-symmetrical analysis [1], [2]. We show how the initial elliptic (electric potential), hyperbolic (charge transport), non-local (photo-ionization) problem can be formulated into two local problems coupled by matching conditions. The approach relies on a multipole expansion of the radiative photo-ionization source term (in two dimensions for cylindrical emitters). The analytical asymptotic matching conditions derived in [2] result in flux continuity conditions at the boundary of the two domains. These coupling conditions are enforced by Lagrange multipliers, within a variational formulation, leading to a hierarchy of non-linear coupled problems. The proposed approach is both monolithic and two-domains: two asymptotic regions, an inner-one associated with corona discharge, and an outer-one, the ion drift region. Numerical convergence and validations of the finite element implementation is provided. A comparison with various experimental results convincingly demonstrate the applicability of the method, which avoids tuning parameters dedicated to each specific configuration, but, on the contrary, exclusively relies on known and measurable physical quantities (e.g., ion mobilities, photo-ionization coefficient, ionization electric field, Townsend discharge coefficient, etc...).},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao26478,

title = {Analytical properties of Graetz modes in parallel and concentric configurations},

author = {Charles Pierre and Franck Plouraboué},

url = {https://oatao.univ-toulouse.fr/26478/},

doi = {10.1007/s11012-020-01192-4},

year  = {2020},

date = {2020-06-01},

journal = {Meccanica},

volume = {55},

pages = {1545--1559},

publisher = {Springer},

abstract = {The generalized Graetz problem refers to stationary convection-diffusion in uni-directional flows. In this contribution we demonstrate the analyticity of generalized Graetz solutions associated with layered domains: either cylindrical (possibly concentric) or parallel. Such configurations are considered as prototypes for heat exchangers devices and appear in numerous applications involving heat or mass transfer. 

The established framework of Graetz modes allows to recast the 3D resolution of the heat transfer into a 2D or even 1D spectral problem. The associated eigen-functions (called Graetz modes) are obtained with the help of a sequence of closure functions that are recursively computed. The spectrum is given by the zeros of an explicit analytical series, the truncation of which allows to approximate the eigenvalues by solving a polynomial equation. Graetz mode computation is henceforth made explicit and can be performed using standard software of formal calculus. It permits a direct and mesh-less computation of the resulting solutions for a broad range of configurations. 

Some solutions are illustrated to showcase the interest of mesh-less analytical derivation of the Graetz 

solutions, useful to validate other numerical approaches.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao25659,

title = {From whole-organ imaging to in-silico blood flow modeling: a new multi-scale network analysis for revisiting tissue functional anatomy},

author = {Pol Kennel and Jules Dichamp and Corinne Barreau and Christophe Guissard and Lise Teyssedre and Jacques Rouquette and Julien Colombelli and Anne Lorsignol and Louis Casteilla and Franck Plouraboué},

url = {https://oatao.univ-toulouse.fr/25659/},

doi = {10.1371/journal.pcbi.1007322},

year  = {2020},

date = {2020-02-01},

urldate = {2020-02-01},

journal = {PLOS Computational Biology},

volume = {16},

number = {2},

pages = {e1007322},

abstract = {We present a multi-disciplinary image-based blood flow perfusion modeling of a whole organ vascular network for analyzing both its structural and functional properties. We show how the use of Light-Sheet Fluorescence Microscopy (LSFM) permits whole-organ micro- vascular imaging, analysis and modelling. By using adapted image post-treatment workflow, we could segment, vectorize and reconstruct the entire micro-vascular network composed of 1.7 million vessels, from the tissue-scale, inside a * 25 × 5 × 1 = 125mm3 volume of the mouse fat pad, hundreds of times larger than previous studies, down to the cellular scale at micron resolution, with the entire blood perfusion modeled. Adapted network analysis revealed the structural and functional organization of meso-scale tissue as strongly connected communities of vessels. These communities share a distinct heterogeneous core region and a more homogeneous peripheral region, consistently with known biological functions of fat tissue. Graph clustering analysis also revealed two distinct robust meso-scale typical sizes (from 10 to several hundred times the cellular size), revealing, for the first time, strongly connected functional vascular communities. These community networks support heterogeneous micro-environments. This work provides the proof of concept that in-silico all-tissue perfusion modeling can reveal new structural and functional exchanges between micro-regions in tissues, found from community clusters in the vascular graph.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao25673,

title = {Mechanical integrity of 3D rough surfaces during contact},

author = {Maxence Bigerelle and Franck Plouraboué and Frederic Robache and Abdeljalil Jourani and Agnes Fabre},

url = {https://oatao.univ-toulouse.fr/25673/},

doi = {10.3390/coatings10010015},

year  = {2019},

date = {2019-12-01},

journal = {Coatings},

volume = {10},

number = {1},

pages = {15},

publisher = {MDPI},

abstract = {Rough surfaces are in contact locally by the peaks of roughness. At this local scale, the pressure of contact can be sharply superior to the macroscopic pressure. If the roughness is assumed to be a random morphology, a well-established observation in many practical cases, mechanical indicators built from the contact zone are then also random variables. Consequently, the probability density function (PDF) of any mechanical random variable obviously depends upon the morphological structure of the surface. The contact pressure PDF, or the probability of damage of this surface can be determined for example when plastic deformation occurs. In this study, the contact pressure PDF is modeled using a particular probability density function, the generalized Lambda distributions (GLD). The GLD are generic and polymorphic. They approach a large number of known distributions (Weibull, Normal, and Lognormal). The later were successfully used to model damage in materials. A semi-analytical model of elastic contact which takes into account the morphology of real surfaces is used to compute the contact pressure. In a first step, surfaces are simulated by Weierstrass functions which have been previously used to model a wide range of surfaces met in tribology. The Lambda distributions adequacy is qualified to model contact pressure. Using these functions, a statistical analysis allows us to extract the probability density of the maximal pressure. It turns out that this density can be described by a GLD. It is then possible to determine the probability that the contact pressure generates plastic deformation.},

note = {This article is an open accessarticle distributed under the terms and conditions of the Creative Commons Attribution(CC BY) license (http://creativecommons.org/licenses/by/4.0/).},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao25639,

title = {Numerical modelling of long flexible fibers in homogeneous isotropic turbulence},

author = {Mostafa Sulaiman and {É}ric Climent and Blaise Delmotte and Pascal Fede and Franck Plouraboué and Gautier Verhille},

url = {https://oatao.univ-toulouse.fr/25639/},

doi = {10.1140/epje/i2019-11894-7},

year  = {2019},

date = {2019-10-01},

journal = {European Physical Journal E},

volume = {42},

number = {132},

publisher = {EDP Sciences},

abstract = {We numerically investigated the transport, deformation and buckling events of an isolated elastic fiber in Taylor-Green vortices and studied the dynamics of long filaments in homogeneous isotropic turbulence. The fiber is modelled by an assembly of spherical beads. The contact between beads enforces the inextensibility of the filament while bending is accounted for by the Gears Bead Model (GBM) proposed by Delmotte et al. (2015). In the cellular Taylor-Green flow, the buckling probability is a function of a dimensionless number, called Sperm number, which is a balance between the compression rate of the flow and the elastic response of the filament. The shapes of the filament and its ability to buckle have been successfully validated through comparisons with experiments from the work by Quennouz et al. (2015). The deformation statistics of long flexible fibers in sustained homogeneous isotropic turbulence were analyzed for various flow and fiber material conditions. Two regimes have been identified depending on the ratio of fiber length to persistence length which is a measure of turbulent forcing to flexibility. The numerical results are in good agreement with existing experimental data (C. Brouzet et al., Phys. Rev. Lett. 112, 

074501 (2014)) validating the assumptions of our model for the configurations we investigated.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao23852,

title = {3D analysis of the whole subcutaneous adipose tissue reveals a complex spatial network of interconnected lobules with heterogeneous browning ability},

author = {Jules Dichamp and Corinne Barreau and Christophe Guissard and Audrey Carrière and Yves Martinez and Xavier Descombes and Luc Pénicaud and Jacques Rouquette and Louis Casteilla and Franck Plouraboué and Anne Lorsignol},

url = {https://rdcu.be/bRNp0

https://oatao.univ-toulouse.fr/23852/},

doi = {10.1038/s41598-019-43130-9},

year  = {2019},

date = {2019-04-01},

urldate = {2019-04-01},

journal = {Scientific Reports},

volume = {9},

pages = {1--13},

publisher = {Nature Publishing Group},

abstract = {Adipose tissue, as the main energy storage organ and through its endocrine activity, is interconnected with all physiological functions. It plays a fundamental role in energy homeostasis and in the development of metabolic disorders. Up to now, this tissue has been analysed as a pool of different cell types with very little attention paid to the organization and putative partitioning of cells. Considering the absence of a complete picture of the intimate architecture of this large soft tissue, we developed a method that combines tissue clearing, acquisition of autofluorescence or lectin signals by confocal microscopy, segmentation procedures based on contrast enhancement, and a new semi-automatic image analysis process, allowing accurate and quantitative characterization of the whole 3D fat pad organization. This approach revealed the unexpected anatomic complexity of the murine subcutaneous fat pad. Although the classical picture of adipose tissue corresponds to a superposition of simple and small ellipsoidal lobules of adipose cells separated by mesenchymal spans, our results show that segmented lobules display complex 3D poly-lobular shapes. Despite differences in shape and size, the number of these poly-lobular subunits is similar from one fat pad to another. Finally, investigation of the relationships of these subunits between each other revealed a never-described organization in two clusters with distinct molecular signatures and specific vascular and sympathetic nerve densities correlating with different browning abilities. This innovative procedure reveals that subcutaneous adipose tissue exhibits a subtle functional heterogeneity with partitioned areas, and opens new perspectives towards understanding its functioning and plasticity.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao23686,

title = {Thermal significance and optimal transfer in vessels bundles is influenced by vascular density},

author = {Jules Dichamp and Frédéric De Gournay and Franck Plouraboué},

url = {https://oatao.univ-toulouse.fr/23686/},

doi = {10.1016/j.ijheatmasstransfer.2018.12.185},

year  = {2019},

date = {2019-04-01},

journal = {International Journal of Heat and Mass Transfer},

volume = {138},

pages = {1--10},

publisher = {Elsevier},

abstract = {A semi-analytic method is used in order to systematically compute stationary 3-D coupled convection-diffusion in various parallel counter-current configurations and evaluate their thermal significance. This semi-analytic method permits a complete exploration of physiologically relevant parameter space associated with the bio-heat transfer of parallel vessels bundles. We analyze thermal significance with various previously proposed criteria. Optimal transfer configurations are found to depend on the vascular density and Péclet numbers. The relevance of these findings for bio-heat modeling in tissues is discussed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao21207,

title = {Flying with ionic wind},

author = {Franck Plouraboué},

url = {https://oatao.univ-toulouse.fr/21207/},

doi = {10.1038/d41586-018-07411-z},

year  = {2018},

date = {2018-11-01},

journal = {Nature},

volume = {563},

pages = {476--477},

publisher = {Nature Publishing Group},

abstract = {Aeroplanes use propellers and turbines, and are typically powered by fossil-fuel combustion. An alternative method of propelling planes has been demonstrated that does not require moving parts or combustion.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao20743,

title = {Toward quantitative three-dimensional microvascular networks segmentation with multiview light-sheet fluorescence microscopy},

author = {Pol Kennel and Lise Teyssedre and Julien Colombelli and Franck Plouraboué},

url = {https://oatao.univ-toulouse.fr/20743/},

doi = {10.1117/1.JBO.23.8.086002},

year  = {2018},

date = {2018-08-01},

journal = {Journal of Biomedical Optics},

volume = {23},

number = {08},

pages = {1--15},

publisher = {Society of Photo-optical Instrumentation Engineers},

abstract = {Three-dimensional (3-D) large-scale imaging of microvascular networks is of interest in various areas of biology and medicine related to structural, functional, developmental, and pathological issues. Light-sheet fluorescence microscopy (LSFM) techniques are rapidly spreading and are now on the way to offer operational solutions for large-scale tissue imaging. This contribution describes how reliable vessel segmentation can be handled from LSFM data in very large tissue volumes using a suitable image analysis workflow. Since capillaries are tubular objects of a few microns scale radius, they represent challenging structures to reliably reconstruct without distortion and artifacts. We provide a systematic analysis of multiview deconvolution image processing workflow to control and evaluate the accuracy of the reconstructed vascular network using various low to high level, metrics. We show that even if low-level structural metrics are sensitive to isotropic imaging enhancement provided by a larger number of views, functional high-level metrics, including perfusion permeability, are less sensitive. Hence, combining deconvolution and registration onto a few number of views appears sufficient for a reliable quantitative 3-D vessel segmentation for their possible use for perfusion modeling.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao20160,

title = {Electrohydrodynamic ionic wind, force field, and ionic mobility in a positive dc wire-to-cylinders corona discharge in air},

author = {Nicolas Monrolin and Olivier Praud and Franck Plouraboué},

url = {https://oatao.univ-toulouse.fr/20160/

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.3.063701},

doi = {10.1103/PhysRevFluids.3.063701},

year  = {2018},

date = {2018-06-01},

urldate = {2018-06-01},

journal = {Physical Review Fluids},

volume = {3},

number = {6},

pages = {063701/1--063701/20},

publisher = {Amercian Physical Society},

abstract = {Ionic wind refers to the acceleration of partially ionized air between two high-voltage electrodes. We study the momentum transfer from ions to air, resulting from ionic wind created by two asymmetric electrodes and producing a net thrust. This electrohydrodynamic (EHD) thrust, has already been measured in previous studies with digital scales. In this study, we provide more insights into the electrohydrodynamic momentum transfer for a wire-to-cylinder(s) positive dc corona discharge. We provide a simple and general theoretical derivation for EHD thrust, which is proportional to the current/mobility ratio and also to an effective distance integrated on the surface of the electrodes. By considering various electrode configurations, our investigation brings out the physical origin of previously obtained optimal configurations, associated with a better tradeoff between Coulomb forcing, friction occurring at the collector, and wake interactions. By measuring two-dimensional velocity fields using particle image velocimetry (PIV), we are able to evaluate the resulting local net force, including the pressure gradient. It is shown that the contribution of velocity fluctuations in the wake of the collecting electrode(s) must be taken into account to recover the net thrust. We confirm the proportionality between the EHD force and the current/mobility ratio experimentally, and evaluate the ion mobility from PIV measurements. A spectral analysis of the velocity fluctuations indicates a dominant frequency corresponding to a Strouhal number of 0.3 based on the ionic wind velocity and the collector size. Finally, the effective mobility of charge carriers is estimated by a PIV based method inside the drift region.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao20744,

title = {Simulations of Brownian tracer transport in squirmer suspensions},

author = {Blaise Delmotte and Eric E Keaveny and {É}ric Climent and Franck Plouraboué},

url = {https://oatao.univ-toulouse.fr/20744/},

doi = {10.1093/imamat/hxy012},

year  = {2018},

date = {2018-02-01},

journal = {IMA Journal of Applied Mathematics},

volume = {83},

number = {4},

pages = {680--699},

publisher = {Oxford University Press},

abstract = {In addition to enabling movement towards environments with favourable living conditions, swimming by microorganisms has also been linked to enhanced mixing and improved nutrient uptake by their populations. Experimental studies have shown that Brownian tracer particles exhibit enhanced diffusion due to the swimmers, while theoretical models have linked this increase in diffusion to the flows generated by the swimming microorganisms, as well as collisions with the swimmers. In this study, we perform detailed simulations based on the force-coupling method and its recent extensions to the swimming and Brownian particles to examine tracer displacements and effective tracer diffusivity in squirmer suspensions. By isolating effects such as hydrodynamic or steric interactions, we provide physical insight into experimental measurements of the tracer displacement distribution. In addition, we extend results to the semi-dilute regime where the swimmer?swimmer interactions affect tracer transport and the effective tracer diffusivity no longer scales linearly with the swimmer volume fraction.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao20121,

title = {New objective measurements of semen wave motion are associated with fertility in sheep},

author = {Ingrid David and Philippa L. Kohnke and Jérôme Fehrenbach and Ana Rita Lopes Simoes and Eric Debreuve and Xavier Descombes and Franck Plouraboué and Pierre Degond and Xavier Druart},

url = {http://www.publish.csiro.au/rd/RD17472

https://oatao.univ-toulouse.fr/20121/},

doi = {10.1071/RD17472},

year  = {2018},

date = {2018-01-01},

urldate = {2018-01-01},

journal = {Reproduction Fertility and Development},

volume = {30},

number = {6},

pages = {889--896},

publisher = {CSIRO Publishing},

abstract = {In sheep, wave motion in semen is currently used by AI centres to select ejaculates for insemination. Despite its low cost, convenience and established ability to predict fertility, the subjectivity of this assessment is a limiting factor for its applicability. The aims of the present study were to establish an objective method for the analysis of wave motion and to assess the associations of objective parameters with fertility after cervical insemination. Collective sperm motion in undiluted semen was observed by phase contrast microscopy at low magnification in a 100-?m deep glass chamber. Images of moving dark waves over a grey background were recorded and analysed by the optic flow method, producing several velocity-related parameters. Turbulence was assessed from the motion of fluorescent polystyrene beads. Among objective parameters, optical flow entropy and the average speed of beads were both able to discriminate ejaculates suitable for insemination. Two synthetic variables of optic flow and bead motion and a global objective variable were computed from linear combinations of individual parameters and compared with the subjective motion score for their predictive value. These were as efficient as the wave motion score for assessing fertility and can be proposed for the assessment of ram semen in routine AI procedures.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao20116,

title = {Revisiting the positive DC corona discharge theory: Beyond Peek's and Townsend's law},

author = {Nicolas Monrolin and Olivier Praud and Franck Plouraboué},

url = {https://aip.scitation.org/doi/10.1063/1.5031780

https://oatao.univ-toulouse.fr/20116/},

doi = {10.1063/1.5031780},

year  = {2018},

date = {2018-01-01},

urldate = {2018-01-01},

journal = {Physics of Plasmas},

volume = {25},

number = {6},

pages = {063503/1--063503/14},

publisher = {AIP Publishing},

abstract = {The classical positive Corona Discharge (CD) theory in cylindrical axisymmetric configuration is revisited in order to find analytically the influence of gas properties and thermodynamic conditions on the corona current. The matched asymptotic expansion of Durbin & Turyn of a simplified but self-consitent problem is performed and explicit analytical solutions are derived. The mathematical derivation permits to express a new positive DC corona current-voltage charachteristic, either chosing dimensionless or dimensional formulation. In dimensional variables the current voltage law and the corona inception voltage explicitly depends on electrodes size and on physical gas properties such as ionization and photoionization parameters. The analytical predictions are successfully confronted with experiments and with Peek's and Townsend's laws. An analytical expression of the corona inception voltage $$backslash$varphi_on$ is proposed, which depends on known values of the physical parameters without adjustable parameters. As a proof of consistency, the classical Townsend current-voltage law $I=C$backslash$varphi($backslash$varphi-$backslash$varphi_on)$ is retrieved by linearizing the non-dimensional analytical solution. 

A brief parametric study showcases the interest of this analytical current model especially for exploring small corona wires or considering various thermodynamic conditions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao17447,

title = {Identification of internal properties of fibres and micro-swimmers},

author = {Franck Plouraboué and E. Ibrahima Thiam and Blaise Delmotte and Éric Climent},

url = {https://oatao.univ-toulouse.fr/17447/

http://rspa.royalsocietypublishing.org/content/473/2197/20160517},

doi = {10.1098/rspa.2016.0517},

year  = {2017},

date = {2017-01-01},

urldate = {2017-01-01},

journal = {Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science},

volume = {473},

number = {2197},

pages = {20160517},

publisher = {The Royal Society},

abstract = {In this paper, we address the identifiability of constitutive parameters of passive or active micro-swimmers. We first present a general framework for describing fibres or micro-swimmers using a bead-model description. Using a kinematic constraint formulation to describe fibres, flagellum or cilia, we find explicit linear relationship between elastic constitutive parameters and generalized velocities from computing contact forces. This linear formulation then permits one to address explicitly identifiability conditions and solve for parameter identification. We show that both active forcing and passive parameters are both identifiable independently but not simultaneously. We also provide unbiased estimators for generalized elastic parameters in the presence of Langevin-like forcing with Gaussian noise using a Bayesian approach. These theoretical results are illustrated in various configurations showing the efficiency of the proposed approach for direct parameter identification. The convergence of the proposed estimators is successfully tested numerically.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao18415,

title = {Electrohydrodynamic thrust for in-atmosphere propulsion},

author = {Nicolas Monrolin and Franck Plouraboué and Olivier Praud},

url = {https://arc.aiaa.org/doi/10.2514/1.J055928

https://oatao.univ-toulouse.fr/18415/},

doi = {10.2514/1.J055928},

year  = {2017},

date = {2017-01-01},

urldate = {2017-01-01},

journal = {AIAA Journal},

volume = {55},

number = {12},

pages = {4296--4305},

publisher = {American Institute of Aeronautics and Astronautics},

abstract = {The electrohydrodynamic thrust generated by wire-cylinder electrodes under high dc voltage is experimentally analyzed. Some recent experimental studies have shown that electrohydrodynamic thrusters produced by corona discharge and ionic wind are able to deliver high thrust-to-power ratio, which reopens prospects for electrohydrodynamic propulsion. From simple considerations based on ultralight aircraft mass, aerodynamics, battery mass, and experimental electrohydrodynamic thrust densities, their potential for applications is showcased. Furthermore, an experimental study is performed, for which the experimental observations are presented in terms of electric field and thrust density. This allows a simplified and synthetic presentation of propulsive properties. Various experimental biases have been identified and corrected. The measure of time-periodic oscillations of the airflow in the back of the thruster pinpoints a possible wake effect due to the impact of ionic wind on electrodes. The variations of the associated drag are studied when varying the position of the collecting electrodes. It is shown that aerodynamic losses can be significant in experimental electrohydrodynamic thrusters.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao16244,

title = {Symmetry-breaking phase transitions in highly concentrated semen},

author = {Adama Kpatagnon Creppy and Franck Plouraboué and Olivier Praud and Xavier Druart and Sébastien Cazin and Hui Yu and Pierre Degond},

url = {https://oatao.univ-toulouse.fr/16244/},

doi = {10.1098/rsif.2016.0575},

year  = {2016},

date = {2016-10-01},

urldate = {2016-10-01},

journal = {Journal of The Royal Society Interface},

volume = {13},

number = {123},

pages = {1--12},

publisher = {The Royal Society Publishing},

abstract = {New experimental evidence of self-motion of a confined active suspension is presented. Depositing fresh semen sample in an annular shaped microfluidic chip leads to a spontaneous vortex state of the fluid at sufficiently large sperm concentration. The rotation occurs unpredictably clockwise or counterclockwise and is robust and stable. Furthermore, for highly active and concentrated semen, richer dynamics can occur such as self-sustained or damped rotation oscillations. Experimental results obtained with systematic dilution provide a clear evidence of a phase transition towards collective motion associated with local alignment of spermatozoa akin to the Vicsek model. A macroscopic theory based on previously derived self-organized hydrodynamics models is adapted to this context and provides predictions consistent with the observed stationary motion.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao14612,

title = {Enhanced evaporation from an oscillating liquid in a capillary tube},

author = {Denis Polezhaev and Paul Duru and Franck Plouraboué},

url = {http://www.sciencedirect.com/science/article/pii/S0017931015303112

https://oatao.univ-toulouse.fr/14612/},

doi = {10.1016/j.ijheatmasstransfer.2015.12.012},

year  = {2016},

date = {2016-04-01},

urldate = {2016-04-01},

journal = {International Journal of Heat and Mass Transfer},

volume = {95},

pages = {288--295},

publisher = {Elsevier},

abstract = {Enhanced evaporation inside a capillary tube into which the liquid/gas meniscus oscillates is experimentally studied. It is found that the meniscus oscillation can markedly level-off the evaporation rate, while keeping an apparent diffusive behaviour. The apparent diffusive coefficient can reach a tenfold increase in the explored range of parameters. The dependence of the effect is studied by varying the capillary tube diameter, the frequency and the amplitude of the liquid oscillations. The parametric dependence of the apparent diffusive coefficient is well captured by the associated dimensionless Péclet number. A nice collapse of the experimental measurements consistent with a quadratic scaling with Péclet number is found. 

Such scaling is suggested by previous theoretical and experimental analysis associated with a Taylor dispersion transport mechanism. Nevertheless the prefactor of those theory is found to under-predict the observed effect by a factor three. This deviation from Taylor's dispersion driven transport predictions is discussed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao15674,

title = {Regionalization of browning revealed by whole subcutaneous adipose tissue imaging},

author = {Corinne Barreau and Elodie Labit and Christophe Guissard and Jacques Rouquette and Marie-Laure Boizeau and Souleymane Gani Koumassi and Audrey Carrière and Yannick Jeanson and Sandra Berger-Müller and Cécile Dromard and Franck Plouraboué and Louis Casteilla and Anne Lorsignol},

url = {http://onlinelibrary.wiley.com/doi/10.1002/oby.21455/full

https://oatao.univ-toulouse.fr/15674/},

doi = {10.1002/oby.21455},

year  = {2016},

date = {2016-03-01},

urldate = {2016-03-01},

journal = {Obesity},

volume = {00},

number = {00},

pages = {1--9},

publisher = {Wiley},

abstract = {Objective: White and brown adipose tissues play a major role in the regulation of metabolic functions. With the explosion of obesity and metabolic disorders, the interest in adipocyte biology is growing constantly. While several studies have demonstrated functional differences between adipose fat pads, especially in their involvement in metabolic diseases, there are no data available on possible heterogeneity within an adipose depot.

Methods: This study investigated the three-dimensional (3-D) organization of the inguinal fat pad in adult mice by combining adipose tissue clearing and autofluorescence signal acquisition by confocal microscopy. In addition, the study analyzed the expression of genes involved in adipocyte biology and browning at the mARN and protein levels in distinct areas of the inguinal adipose tissue, in control conditions and after cold exposure. 

Results: Semiautomated 3-D image analysis revealed an organization of the fat depot showing two regions: the core was structured into segmented lobules, whereas the periphery appeared unsegmented. Perilipin immunostaining showed that most of the adipocytes located in the core region had smaller lipid droplets, suggesting a brown-like phenotype. qPCR analysis showed a higher expression of the browning markers Ucp1, Prdm16, Ppargc1a, and Cidea in the core region than at the periphery. Finally, cold exposure induced upregulation of thermogenic gene expression associated with an increase of UCP1 protein, specifically in the core region of the inguinal fat depot. 

Conclusions: Altogether, these data demonstrate a structural and functional heterogeneity of the inguinal fat pad, with an anatomically restricted browning process in the core area.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao16621,

title = {Theoretical and numerical analysis of counter-flow parallel convective exchangers considering axial diffusion},

author = {Jules Dichamp and Frédéric de Gournay and Franck Plouraboué},

url = {https://oatao.univ-toulouse.fr/16621/

http://www.sciencedirect.com/science/article/pii/S0017931015317038},

doi = {10.1016/j.ijheatmasstransfer.2016.09.019},

year  = {2016},

date = {2016-01-01},

urldate = {2016-01-01},

journal = {International Journal of Heat and Mass Transfer},

volume = {107},

pages = {154-167},

publisher = {Elsevier},

abstract = {We perform a systematic analysis of heat transfer in a counter-current three dimensional convective exchanger, when the inlet/outlet influence is fully taken into account. The analysis, carried out for constant fluid properties, considers the various influences of the fluid/solid conductivity, the imposed convection, inlet/outlet far-field conditions, and lateral boundary conditions. Using a generalized Graetz mode decomposition which permits to consider, both transverse and longitudinal diffusion influence in the exchanger as well as in the inlets/outlets, we put forward several salient generic features of convection/conduction heat transfer. In all cases we found an optimal Péclet number for the cold or hot effectiveness. Even if, as expected, the larger the Péclet the larger the Nusselt number, high transfer performances are found to be poorly efficient and/or to necessitate non-compact elongated exchangers. Performance degradation arising at high Péclet number are found to be related to a "convective leaks" taking place within outlets. A fully developed regime occurs at large Péclet and/or for long exchangers, which is fully determined by the first eigenvalue of the generalized Graetz mode decomposition, which is an extension of classical Graetz analysis. Numerical results are found consistent with a generalized linear relation between effectiveness and the number of heat transfer units asymptotically established in the convection dominated regime. This study opens new perspectives for micro-heat exchangers where moderate convection provides the best effectiveness and compactness. This contribution is also useful for giving reference solutions to counter-flow exchangers with realistic inlet/outlet boundary conditions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao14290,

title = {Large-scale simulation of steady and time-dependent active suspensions with the force-coupling method},

author = {Blaise Delmotte and Eric Keaveny and Franck Plouraboué and {É}ric Climent},

url = {https://oatao.univ-toulouse.fr/14290/},

doi = {10.1016/j.jcp.2015.09.020},

year  = {2015},

date = {2015-12-01},

urldate = {2015-12-01},

journal = {Journal of Computational Physics},

volume = {302},

pages = {524--547},

publisher = {Elsevier},

abstract = {We present a new development of the force-coupling method (FCM) to address the accurate simulation of a large number of interacting micro-swimmers. Our approach is based on the squirmer model, which we adapt to the FCM framework, resulting in a method that is suitable for simulating semi-dilute squirmer suspensions. Other effects, such as steric interactions, are considered with our model. We test our method by comparing the velocity field around a single squirmer and the pairwise interactions between two squirmers with exact solutions to the Stokes equations and results given by other numerical methods. We also illustrate our method's ability to describe spheroidal swimmer shapes and biologically-relevant time-dependent swimming gaits. We detail the numerical algorithm used to compute the hydrodynamic coupling between a large collection (10^4-10^5) of micro-swimmers. Using this methodology, we investigate the emergence of polar order in a suspension of squirmers and show that for large domains, both the steady-state polar order parameter and the growth rate of instability are independent of system size. These results demonstrate the effectiveness of our approach to achieve near continuum-level results, allowing for better comparison with experimental measurements while complementing and informing continuum models.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao14247,

title = {Mass sperm motility is associated with fertility in sheep},

author = {Ingrid David and Philippa L. Kohnke and Gilles Lagriffoul and Olivier Praud and Franck Plouraboué and Pierre Degond and Xavier Druart},

url = {https://oatao.univ-toulouse.fr/14247/

https://www.sciencedirect.com/science/article/pii/S0378432015300014},

doi = {10.1016/j.anireprosci.2015.08.006},

year  = {2015},

date = {2015-10-01},

urldate = {2015-10-01},

journal = {Animal Reproduction Science},

volume = {161},

pages = {75--81},

publisher = {Elsevier},

abstract = {The study was to focus on the relationship between wave motion (mass sperm motility, measured by a mass sperm motility score, manually assessed by artificial insemination (AI) center operators) and fertility in male sheep. A dataset of 711,562 artificial inseminations performed in seven breeds by five French AI centers during the 2001?2005 time period was used for the analysis. Factors influencing the outcome of the insemination, which is a binary response observed at lambing of either success (1) or failure (0), were studied using a joint model within each breed and AI center (eight separate analyses). The joint model is a multivariate model where all information related to the female, the male and the insemination process were included to improve the estimation of the factor effects. Results were consistent for all analyses. The male factors affecting AI results were the age of the ram and the mass motility. After correction for the other factors of variation, the lambing rate increased quasi linearly from three to more than ten points with the mass sperm motility score depending on the breed and the AI center. The consistency of the relationship for all breeds indicated that mass sperm motility is predictive of the fertility resulting when sperm are used from a specific ejaculate. Nonetheless, predictability could be improved if an objective measurement of mass sperm motility were available as a substitute for the subjective scoring currently in use in AI centers.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao14317,

title = {Turbulence of swarming sperm},

author = {Adama Kpatagnon Creppy and Olivier Praud and Xavier Druart and Philippa L. Kohnke and Franck Plouraboué},

url = {https://oatao.univ-toulouse.fr/14317/

http://journals.aps.org/pre/pdf/10.1103/PhysRevE.92.032722},

doi = {10.1103/PhysRevE.92.032722},

year  = {2015},

date = {2015-09-01},

urldate = {2015-09-01},

journal = {Physical Review E},

volume = {92},

number = {3},

pages = {n/a},

publisher = {American Physical Society},

abstract = {Collective motion of self-sustained swarming flows has recently provided examples of small-scale turbulence arising where viscous effects are dominant. We report the first observation of universal enstrophy cascade in concentrated swarming sperm consistent with a body of evidence built from various independent measurements. We found a well-defined k-3 power-law decay of a velocity field power spectrum and relative dispersion of small beads consistent with theoretical predictions in 2D turbulence. Concentrated living sperm displays long-range, correlated whirlpool structures of a size that provides an integral scale of turbulence. We propose a consistent explanation for this quasi-2D turbulence based on self-structured laminated flow forced by steric interactions and alignment, a state of active matter that we call "swarming liquid crystal". We develop scaling arguments consistent with this interpretation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao13585,

title = {A general formulation of Bead Models applied to flexible fibers and active filaments at low Reynolds number},

author = {Blaise Delmotte and {É}ric Climent and Franck Plouraboué},

url = {https://oatao.univ-toulouse.fr/13585/

http://www.sciencedirect.com/science/article/pii/S0021999115000303},

doi = {10.1016/j.jcp.2015.01.026},

year  = {2015},

date = {2015-04-01},

urldate = {2015-04-01},

journal = {Journal of Computational Physics},

volume = {286},

pages = {14--37},

publisher = {Elsevier},

abstract = {This contribution provides a general framework to use Lagrange multipliers for the simulation of low Reynolds number fiber dynamics based on Bead Models (BM). This formalism provides an efficient method to account for kinematic constraints. We illustrate, with several examples, to which extent the proposed formulation offers a flexible and versatile framework for the quantitative modeling of flexible fibers deformation and rotation in shear flow, the dynamics of actuated filaments and the propulsion of active swimmers. Furthermore, a new contact model called Gears Model is proposed and successfully tested. It avoids the use of numerical artifices such as repulsive forces between adjacent beads, a source of numerical difficulties in the temporal integration of previous Bead Models.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao11164,

title = {Numerical computation of 3D heat transfer in complex parallel heat exchangers using generalized Graetz modes},

author = {Charles Pierre and Julien Bouyssier and Frédéric De Gournay and Franck Plouraboué},

url = {https://oatao.univ-toulouse.fr/11164/

http://www.sciencedirect.com/science/article/pii/S0021999114001636?via=ihub},

doi = {10.1016/j.jcp.2014.02.037},

year  = {2014},

date = {2014-07-01},

urldate = {2014-07-01},

journal = {Journal of Computational Physics},

volume = {268},

pages = {84--105},

publisher = {Elsevier},

abstract = {We propose and develop a variational formulation dedicated to the simulation of parallel convective heat exchanger that handles possibly complex input/output conditions as well as connection between pipes. It is based on a spectral method that allows to re-cast three-dimensional heat exchangers into a two-dimensional eigenvalue problem, named the generalized Graetz problem. Our formulation handles either convective, adiabatic, or prescribed temperature at the entrance or at the exit of the exchanger. This formulation is robust to mode truncation, offering a huge reduction in computational cost, and providing insights into the most contributing structure to exchanges and transfer. Several examples of heat exchangers are analyzed, their numerical convergence is tested and the numerical efficiency of the approach is illustrated in the case of Poiseuille flow in tubes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao10965,

title = {Shape optimization for the generalized Graetz problem},

author = {Frédéric De Gournay and Jérôme Fehrenbach and Franck Plouraboué},

url = {https://oatao.univ-toulouse.fr/10965/

http://link.springer.com/article/10.1007/s00158-013-1032-4},

doi = {10.1007/s00158-013-1032-4},

year  = {2014},

date = {2014-01-01},

urldate = {2014-01-01},

journal = {Structural and Multidisciplinary Optimization},

publisher = {Springer},

abstract = {We apply shape optimization tools to the generalized Graetz problem which is a convection-diffusion equation. The problem boils down to the optimization of generalized eigen values on a two phases domain. Shape sensitivity analysis is performed with respect to the evolution of the interface between the fluid and solid phase. In particular physical settings, counterexamples where there is no optimal domains are exhibited. Numerical examples of optimal domains with different physical parameters and constraints are presented. Two different numerical methods (level-set and mesh-morphing) are show-cased and compared.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao9357,

title = {Mathematical analysis of parallel convective exchangers with general lateral boundary conditions using generalized graetz modes},

author = {Julien Bouyssier and Charles Pierre and Franck Plouraboué},

url = {https://oatao.univ-toulouse.fr/9357/

http://www.worldscientific.com/worldscinet/m3as},

doi = {10.1142/S0218202513500620},

year  = {2013},

date = {2013-08-01},

urldate = {2013-08-01},

journal = {Mathematical Models and Methods in Applied Sciences},

pages = {1--39},

publisher = {World Scientific Publishing},

abstract = {We propose a mathematical analysis of parallel convective exchangers for any general but longitudinally invariant domains. We analyze general Dirichlet or Neumann prescribed boundary conditions at the outer solid domain. Our study provides general mathematical expressions for the solution of convection/diffusion problems. Explicit form of generalized solutions along longitudinal coordinate are found from convoluting elementary base Graetz mode with the applied sources at the boundary. In the case of adiabatic zero flux counter-current configuration, we recover the longitudinally linearly varying solution associated with the zeroth eigenmode which can be considered as the fully developed behavior for heat-exchangers. We also provide general expression for the infinite asymptotic behavior of the solutions which depends on simple parameters such as total convective flux, outer domain perimeter and the applied boundary conditions. Practical considerations associated with the numerical precision of truncated mode decomposition is also analyzed in various configurations for illustrating the versatility of the formalism. Numerical quantities of interest are investigated, such as fluid/solid internal and external fluxes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao9314,

title = {Collective motility of sperm in confined cells},

author = {Adama Kpatagnon Creppy and Franck Plouraboué and Olivier Praud and Alexis Viel},

url = {https://oatao.univ-toulouse.fr/9314/

http://www.tandfonline.com/doi/abs/10.1080/10255842.2013.815899},

doi = {10.1080/10255842.2013.815899},

year  = {2013},

date = {2013-08-01},

urldate = {2013-08-01},

journal = {Computer Methods in Biomechanics and Biomedical Engineering},

volume = {16},

number = {supp. 1},

pages = {11--12},

publisher = {Taylor & Francis},

abstract = {Mammalian fertility analysis is an important industrial issue because of the selection for breeding. This is one reason, beside fundamental interest, for which many studies analyse the individual motion of the spermatozoon (Gaffney et al. 2011). On the other hand, more recent reviews suggest that neither individual motion indicators or molecular markers can be clearly correlated to fertility (Kastelic and Thundathil 2008; Nathali and Turek 2011). This is why the industry still uses the scoring of sperm motility from the observation of semen sessile drop with a phase-contrast microscope. This observation of pure semen displays wave motion associated with millions of sperm moving together in circular waves and whirlpools. The moving speed, deformation and size of whirlpools were ranked and scored. Similar collective movements have also been observed in different biological suspensions above a certain concentration (Sokolov et al. 2007). But until today, there has been no clear analysis of the origin of the observed whirlpools dynamics in semen. In this article, we provide new insights on the origin of whirlpools. As the sessile drops do not permit a careful control of the micro-hydrodynamic boundary conditions associated with surface tension variations, we investigate collective effects in controlled rectangular cells confined span wise with 20 and 100mm depth. We mainly analyse the influence of the confinement and the concentration on the appearance of whirlpools.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao9315,

title = {Hydrodynamic interactions among large populations of swimming micro-organisms},

author = {Blaise Delmotte and {É}ric Climent and Franck Plouraboué},

url = {https://oatao.univ-toulouse.fr/9315/

http://www.tandfonline.com/doi/abs/10.1080/10255842.2013.815881},

doi = {10.1080/10255842.2013.815881},

year  = {2013},

date = {2013-08-01},

urldate = {2013-08-01},

journal = {Computer Methods in Biomechanics and Biomedical Engineering},

volume = {16},

number = {supp. 1},

pages = {6--8},

publisher = {Taylor & Francis},

abstract = {Bio-convection, biofilm forming or mechanics of reproduction are connected to the motility and collective behaviour of micro-organisms. For instance, spermatozoa suspensions exhibit coherent motion whose frequency and lifespan are strongly correlated to semen fertility (Moore et al. 2002). As interplays in many-bodied systems result in intricate patterns, the understanding of these requires an in-depth knowledge of the suspension microstructure and statistics. Representative and reliable statistics require a large number Np of interactive swimmers that many simulation methods can hardly afford [e.g. Np ? 40 in Mehandia and Nott (2008) or Np # 216 in Ishikawa et al. (2008)]. In the following, a spherical swimmer model is derived from the classical low Reynolds number framework and implemented in the force-coupling method (FCM) for large populations. Resulting statistics reveals non-trivial spatial arrangements of swimmers depending on their swimming gait.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao8933,

title = {On the normalization of cerebral blood flow},

author = {Romain Guibert and Caroline Fonta and François Estève and Franck Plouraboué},

url = {www.nature.com/jcbfm/journal/v33/n5/full/jcbfm201339a.html

https://oatao.univ-toulouse.fr/8933/},

doi = {10.1038/jcbfm.2013.39},

year  = {2013},

date = {2013-05-01},

urldate = {2013-05-01},

journal = {Journal of Cerebral Blood Flow & Metabolism},

volume = {33},

pages = {669--672},

publisher = {Nature Publishing Group},

abstract = {Cerebral blood ?ow (CBF) is the most common parameter for the quanti?cation of brain?s function. Literature data indicate a widespread dispersion of values that might be related to some differences in the measurement conditions that are not properly taken into account in CBF evaluation. Using recent high-resolution imaging of the complete cortical microvasculature of primate brain, we perform extensive numerical evaluation of the cerebral perfusion. We show that blood perfusion associated with intravascular tracers should be normalized by the surface of the voxel rather than by its volume and we consistently test this result on the available literature data.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao8538,

title = {Broadband converging plasmon resonance at a conical nanotip},

author = {Yunshan Wang and Franck Plouraboué and Hsueh-Chia Chang},

url = {https://oatao.univ-toulouse.fr/8538/},

doi = {10.1364/OE.21.006609},

year  = {2013},

date = {2013-01-01},

journal = {Optics Express},

volume = {21},

number = {5},

pages = {6609--6617},

publisher = {Optical Society of America},

abstract = {We propose an analytical theory which predicts that Converging Plasmon Resonance (CPR) at conical nanotips exhibits a red-shifted and continuous band of resonant frequencies and suggests potential application of conical nanotips in various fields, such as plasmonic solar cells, photothermal therapy, tip-enhanced Raman and other spectroscopies. The CPR modes exhibit superior confinement and ten times broader scattering 

bandwidth over the entire solar spectrum than smooth nano-structures. The theory also explicitly connects the optimal angles and resonant optical frequencies to the material permittivities, with a specific optimum half 

angle that depends only on the real permittivity for high-permittivity and low-loss materials.},

note = {Thanks to Optical Society of America. The original publication is available at http://www.opticsinfobase.org/},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao6572,

title = {Simple Patient-Based Transmantle Pressure and Shear Estimate From Cine Phase-Contrast MRI in Cerebral Aqueduct},

author = {Gérald Bardan and Franck Plouraboué and Mokhtar Zagzoule and Olivier Balédent},

url = {http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6263280

https://oatao.univ-toulouse.fr/6572/},

doi = {10.1109/TBME.2012.2210716},

year  = {2012},

date = {2012-10-01},

urldate = {2012-10-01},

journal = {IEEE Transactions on Biomedical Engineering},

volume = {59},

number = {10},

pages = {2874--2883},

publisher = {IEEE},

abstract = {From measurements of the oscillating flux of the cerebrospinal fluid (CSF) in the aqueduct of Sylvius, we elaborate a patient-based methodology for transmantle pressure (TRP) and shear evaluation. High-resolution anatomical magnetic resonance imaging first permits a precise 3-D anatomical digitalized reconstruction of the Sylvius aqueduct shape. From this, a very fast approximate numerical flow computation, nevertheless consistent with analytical predictions, is developed. Our approach includes the main contributions of inertial effects coming from the pulsatile flow and curvature effects associated with the aqueduct bending. Integrating the pressure along the aqueduct longitudinal center-line enables the total dynamic hydraulic admittances of the aqueduct to be evaluated, which is the pre-eminent contribution to the CSF pressure difference between the lateral ventricles and the subarachnoidal spaces also called the TRP. The application of the method to 20 healthy human patients validates the hypothesis of the proposed approach and provides a first database for normal aqueduct CSF flow. Finally, the implications of our results for modeling and evaluating intracranial cerebral pressure are discussed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao6856,

title = {Pressure drop reconstruction in the aqueduct of sylvius from MRI acquisitions},

author = {Gérald Bardan and Franck Plouraboué and Mokhtar Zagzoule and Olivier Balédent},

url = {https://oatao.univ-toulouse.fr/6856/},

doi = {10.1080/10255842.2012.713735},

year  = {2012},

date = {2012-09-01},

journal = {Computer Methods in Biomechanics and Biomedical Engineering},

volume = {15},

pages = {79--80},

publisher = {Taylor & Francis},

abstract = {Pressure drop reconstruction in the aqueduct of sylvius 

from MRI acquisitions},

note = {Published in a special issue (Supplement 1 : 37th Congress of the Societe de Biomecanique). Open access is not allowed for this article.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao6855,

title = {Flow and particles deposition in anatomically realistic airways},

author = {Tian Xiong and Hassan Ilmi and Yannick Hoarau and Philippe Choquet and Christian Goetz and Andreas Fouras and Stephen Dubsky and Marianna Braza and Sylvie Saintlos-Brillac and Franck Plouraboué and David Lo Jacono},

url = {https://oatao.univ-toulouse.fr/6855/},

doi = {10.1080/10255842.2012.713731},

year  = {2012},

date = {2012-09-01},

urldate = {2012-09-01},

journal = {Computer Methods in Biomechanics and Biomedical Engineering},

volume = {15},

pages = {56--58},

publisher = {Taylor & Francis},

abstract = {The aerosol particles present in our environment are identified as increasingly risk factors for the human health. 

In particular, small particles that reach the surface of gas exchange in the alveolar region of lungs are considered most harmful to health.},

note = {Published in a special issue (Supplement 1 : 37th Congress of the Societe de Biomecanique).

Open access not allowed for this article.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao6021,

title = {Coupling and robustness of intra-cortical vascular territories},

author = {Romain Guibert and Caroline Fonta and Laurent Risser and Franck Plouraboué},

url = {http://www.sciencedirect.com/science/article/pii/S1053811912004260

https://oatao.univ-toulouse.fr/6021/},

doi = {10.1016/j.neuroimage.2012.04.030},

year  = {2012},

date = {2012-08-01},

urldate = {2012-08-01},

journal = {NeuroImage},

volume = {62},

number = {1},

pages = {408--417},

publisher = {Elsevier},

abstract = {Vascular domains have been described as being coupled to neuronal functional units enabling dynamic blood supply to the cerebral cyto-architecture. Recent experiments have shown that penetrating arterioles of the grey matter are the building blocks for such units. Nevertheless, vascular territories are still poorly known, as the collection and analysis of large three-dimensional micro-vascular networks are difficult. By using an exhaustive reconstruction of the micro-vascular network in an 18 mm 3 volume of marmoset cerebral cortex, we numerically computed the blood flow in each blood vessel. We thus defined arterial and venular territories and examined their overlap. A large part of the intracortical vascular network was found to be supplied by several arteries and drained by several venules. We quantified this multiple potential to compensate for deficiencies by introducing a new robustness parameter. Robustness proved to be positively correlated with cortical depth and a systematic investigation of coupling maps indicated local patterns of overlap between neighbouring arteries and neighbouring venules. However, arterio-venular coupling did not have a spatial pattern of overlap but showed locally preferential functional coupling, especially of one artery with two venules, supporting the notion of vascular units. We concluded that intra-cortical perfusion in the primate was characterised by both very narrow functional beds and a large capacity for compensatory redistribution, far beyond the nearest neighbour collaterals.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao6558,

title = {The Generalized Graetz Problem in Finite Domains},

author = {Jérôme Fehrenbach and Frédéric De Gournay and Charles Pierre and Franck Plouraboué},

url = {https://epubs.siam.org/doi/10.1137/11082542X

https://oatao.univ-toulouse.fr/6558/},

doi = {10.1137/11082542X},

year  = {2012},

date = {2012-01-01},

urldate = {2012-01-01},

journal = {SIAM Journal on Applied Mathematics},

volume = {72},

number = {1},

pages = {99--123},

publisher = {Society for Industrial and Applied Mathematics},

abstract = {We consider the generalized Graetz problem associated with stationary convection-diffusion inside a domain having any regular three-dimensional translationally invariant section and finite or semi-infinite extent. Our framework encompasses any previous extended and conjugated Graetz generalizations and provides theoretical bases for computing the orthogonal set of generalized two-dimensional Graetz modes. The theoretical framework includes both heterogeneous and possibly anisotropic diffusion tensors. In the case of semi-infinite domains, the existence of a bounded solution is shown from the analysis of two-dimensional operator eigenvectors which form a basis of L2 . In the case of finite domains a similar basis can be exhibited, and the mode?s amplitudes can be obtained from the inversion of newly defined finite domain operator. Our analysis includes both the theoretical and practical issues associated with this finite domain operator inversion as well as its interpretation as a multireflection image method. Error estimates are provided when numerically truncating the spectrum to a finite number of modes. Numerical examples are validated for reference configurations and provided in nontrivial cases. Our methodology shows how to map the solution of stationary convection-diffusion problems in finite three-dimensional domains into a two-dimensional operator spectrum, which leads to a drastic reduction in computational cost.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5465,

title = {Electrolyte Stability in a Nanochannel with Charge Regulation},

author = {Cédric Beaume and Franck Plouraboué and Alain Bergeon and Edgar Knobloch},

url = {https://pubs.acs.org/doi/10.1021/la2018488

https://oatao.univ-toulouse.fr/5465/},

doi = {10.1021/la2018488},

year  = {2011},

date = {2011-01-01},

urldate = {2011-01-01},

journal = {Langmuir},

volume = {27},

number = {17},

pages = {11187--11198},

publisher = {American Chemical Society},

abstract = {The stability of an electrolyte confined in one dimension between two solid surfaces is analyzed theoretically in the case where overlapping double layers produce nontrivial interactions. Within the Poisson Boltzmann Nernst Planck 

description of the electrostatic interaction and transport of electrical charges, the presence of Stern layers can enrich the set of possible solutions. 

Our analytical and numerical study of the stability properties of the trivial state of this system identified an 

instability to a new antisymmetric state. This state is stable for a range of gap widths that depends on the Debye and Stern lengths, but for smaller gap widths, where the Stern layers overlap, a second transition takes place and the stable nontrivial solution diverges. The origin of this divergence is explained and its properties analyzed 

using asymptotic techniques which are in good agreement with numerical results. The relevance of our results to confined electrolytes at nanometer scales is discussed in the context of energy storage in nanometric systems.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5467,

title = {Steady streaming confined between three-dimensional wavy surfaces},

author = {Romain Guibert and Franck Plouraboué and Alain Bergeon},

url = {https://oatao.univ-toulouse.fr/5467/},

doi = {10.1017/S0022112010001436},

year  = {2010},

date = {2010-08-01},

journal = {Journal of Fluid Mechanics},

volume = {657},

pages = {430--455},

publisher = {Cambridge University Press},

abstract = {We present a theoretical and numerical study of three-dimensional pulsatile confined flow between two rigid horizontal surfaces separated by an average gap h, and having three-dimensional wavy shapes with arbitrary amplitude ensuremathsigma h where ensuremathsigma $sim$ O(1), but long-wavelength variations ensuremathłambda, with h/ensuremathłambda 1. We are interested in pulsating flows with moderate inertial effect arising from the Reynolds stress due to the cavity non-parallelism. We analyse the inertial steady-streaming and the second harmonic flows in a lubrication approximation. The dependence of the three-dimensional velocity field in the transverse direction is analytically obtained for arbitrary Womersley numbers and possibly overlapping Stokes layers. The horizontal dependence of the flow is solved numerically by computing the first two pressure fields of an asymptotic expansion in the small inertial limit. We study the variations of the flow structure with the amplitude, the channel's wavelength and the Womersley number for various families of three-dimensional channels. The steady-streaming flow field in the horizontal plane exhibits a quadrupolar vortex, the size of which is adjusted to the cavity wavelength. When increasing the wall amplitude, the wavelengths characterizing the channel or the Womersley number, we find higher-order harmonic flow structures, the origin of which can either be inertially driven or geometrically induced. When some of the channel symmetries are broken, a steady-streaming current appears which has a quadratic dependence on the pressure drop, the amplitude of which is linked to the Womersley number.},

note = {Thanks to Cambridge University Press. The definitive version is available at http://journals.cambridge.org. The original PDF of the article can be found at Journal of Fluid Mechanics website : http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=7862904},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5466,

title = {Cerebral blood flow modeling in primate cortex},

author = {Romain Guibert and Caroline Fonta and Franck Plouraboué},

url = {http://www.nature.com/jcbfm/journal/v30/n11/full/jcbfm2010105a.html

https://oatao.univ-toulouse.fr/5466/},

doi = {10.1038/jcbfm.2010.105},

year  = {2010},

date = {2010-07-01},

urldate = {2010-07-01},

journal = {Journal of Cerebral Blood Flow & Metabolism},

volume = {30},

number = {11},

pages = {1860--1873},

publisher = {Nature Publishing Group},

abstract = {We report new results on blood flow modeling over large volumes of cortical gray matter of primate brain. We propose a network method for computing the blood flow, which handles realistic boundary conditions, complex vessel shapes, and complex nonlinear blood rheology. From a detailed comparison of the available models for the blood flow rheology and the phase separation effect, we are able to derive important new results on the impact of network structure on blood pressure, hematocrit, and flow distributions. Our findings show that the network geometry (vessel shapes and diameters), the boundary conditions associated with the arterial inputs and venous outputs, and the effective viscosity of the blood are essential components in the flow distribution. In contrast, we show that the phase separation effect has a minor function in the global microvascular hemodynamic behavior. The behavior of the pressure, hematocrit, and blood flow distributions within the network are described through the depth of the primate cerebral cortex and are discussed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5016,

title = {Steady streaming confined between three-dimensional wavy surfaces},

author = {Romain Guibert and Franck Plouraboué and Alain Bergeon},

url = {https://oatao.univ-toulouse.fr/5016/},

doi = {10.1017/S0022112010001436},

year  = {2010},

date = {2010-03-01},

journal = {Journal of Fluid Mechanics},

volume = {657},

pages = {430--455},

publisher = {Cambridge University Press},

abstract = {We present a theoretical and numerical study of three-dimensional pulsatile confined flow between two rigid horizontal surfaces separated by an average gap h, and having three-dimensional wavy shapes with arbitrary amplitude ensuremathsigma h where ensuremathsigma $sim$ O(1), but long-wavelength variations ensuremathłambda, with h/ensuremathłambda 1. We are interested in pulsating flows with moderate inertial effect arising from the Reynolds stress due to the cavity non-parallelism. We analyse the inertial steady-streaming and the second harmonic flows in a lubrication approximation. The dependence of the three-dimensional velocity field in the transverse direction is analytically obtained for arbitrary Womersley numbers and possibly overlapping Stokes layers. The horizontal dependence of the flow is solved numerically by computing the first two pressure fields of an asymptotic expansion in the small inertial limit. We study the variations of the flow structure with the amplitude, the channel's wavelength and the Womersley number for various families of three-dimensional channels. The steady-streaming flow field in the horizontal plane exhibits a quadrupolar vortex, the size of which is adjusted to the cavity wavelength. When increasing the wall amplitude, the wavelengths characterizing the channel or the Womersley number, we find higher-order harmonic flow structures, the origin of which can either be inertially driven or geometrically induced. When some of the channel symmetries are broken, a steady-streaming current appears which has a quadratic dependence on the pressure drop, the amplitude of which is linked to the Womersley number.},

note = {Thanks to Cambridge University Press editor. The definitive version is available at http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=7862904},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5459,

title = {A New Approach to Model Confined Suspensions Flows in Complex Networks: Application to Blood Flow},

author = {Romain Guibert and Caroline Fonta and Franck Plouraboué},

url = {http://www.springerlink.com/content/kj72721r5783638w/?MUD=MP

https://oatao.univ-toulouse.fr/5459/},

doi = {10.1007/s11242-009-9492-0},

year  = {2010},

date = {2010-01-01},

urldate = {2010-01-01},

journal = {Transport in Porous Media},

volume = {83},

number = {1},

pages = {171--194},

publisher = {Springer},

abstract = {The modeling of blood flows confined in micro-channels or micro-capillary beds depends on the interactions between the cell-phase, plasma and the complex geometry of the network. In the case of capillaries or channels having a high aspect ratio (their longitudinal size is much larger than their transverse one), this modeling is much simplified from the use of a continuous description of fluid viscosity as previously proposed in the literature. Phase separation or plasma skimming effect is a supplementary mechanism responsible for the relative distribution of the red blood cell's volume density in each branch of a given bifurcation. Different models have already been proposed to connect this effect to the various hydrodynamics and geometrical parameters at each bifurcation. We discuss the advantages and drawbacks of these models and compare them to an alternative approach for modeling phase distribution in complex channels networks. The main novelty of this new formulation is to show that albeit all the previous approaches seek for a local origin of the phase segregation phenomenon, it can arise from a global non-local and nonlinear structuration of the flow inside the network. This new approach describes how elementary conservation laws are sufficient principles (rather than the complex arametric models previously proposed) to provide non local phase separation. Spatial variations of the hematocrit field thus result from the topological complexity of the network as well as nonlinearities arising from solving a new free boundary problem associated with the ?ux and mass conservation. This network model approach could apply to model blood flow distribution either on arti?cial micro-models, micro-fluidic networks, or realistic reconstruction of biological micro-vascular networks.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao9192,

title = {Le réseau micro-vasculaire structure la distribution de la pression sanguine},

author = {Romain Guibert and Caroline Fonta and Franck Plouraboué},

url = {https://www.mechanics-industry.org/articles/meca/pdf/2009/03/mi0021-2009.pdf

https://oatao.univ-toulouse.fr/9192/},

doi = {10.1051/meca/2009061},

year  = {2009},

date = {2009-05-01},

urldate = {2009-05-01},

journal = {Mécanique & Industries},

volume = {10},

number = {3-4},

pages = {255--260},

publisher = {EDP Sciences},

abstract = {Cerebral micro-vascular networks control the blood pressure distribution when considering in vitro blood rheology models. Blood rheology is complex and non-linear. In small vessels, the effective viscosity variations are important due to red blood cells packing in capillaries, the so-called Frahræus-Lindquist effect, whilst concomitantly phase segregation appears in bifurcations. Direct numerical simulations of different non-linear rheological models of the blood are performed on realistic three-dimensional micro-vascular networks. These simulations exhibit two significant results. First, various rheological models lead to very similar pressure distribution over the whole range of physiologically relevant hematocrits. Secondly, different models for phase segregation lead to very distinct hematocrit distributions in the micro-vacular network. Nevertheless, the hematocrit distribution very weakly affects the pressure distribution. Hence, our results suggest that the micro-vacular network structure mainly controls the pressure distribution in micro-circulation, whilst the effect of hematocrit distribution is weak.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5464,

title = {A 3D-investigation shows that angiogenesis in primate cerebral cortex mainly occurs at capillary level},

author = {Laurent Risser and Franck Plouraboué and Peter Cloetens and Caroline Fonta},

url = {http://www.sciencedirect.com/science/journal/07365748

https://oatao.univ-toulouse.fr/5464/},

doi = {10.1016/j.ijdevneu.2008.10.006},

year  = {2009},

date = {2009-04-01},

urldate = {2009-04-01},

journal = {International Journal of Developmental Neuroscience},

volume = {27},

number = {2},

pages = {185--196},

publisher = {Elsevier},

abstract = {This paper describes the use of a new 3D high-resolution imaging technique dedicated to functional vessels for a systematic quantitative study of angiogenesis in the primate cortex. We present a new method which permits, using synchrotron X-ray micro-tomography imaging, the identi?cation of micro-vascular components as well as their automatic numerical digitalization and extraction from very large 3D image analysis and post-treatments. This method is used to analyze various levels of micro-vascular 

organization and their postnatal modi?cations. Comparing newborn- and adult marmosets, we found an increase in vascular volume (270%), exchange surface (260%) and vessel length (290%) associated to a decrease in distances between vessel and tissue (32%). The increase in relative vascular volumes between the two ages, examined through the whole cortical depth, has been found to be mainly sustained by 

events occurring at the capillary level, and only marginally at the perforating vessel level. This work 

shows that the postnatal cortical maturation classically described in terms of synaptogenesis, gliogenesis and connectivity plasticity is accompanied by an intensive remodeling of micro-vascular patterns.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5463,

title = {Numerical Analysis of a New Mixed Formulation for Eigenvalue Convection-Diffusion Problems},

author = {Charles Pierre and Franck Plouraboué},

url = {https://oatao.univ-toulouse.fr/5463/},

doi = {10.1137/080736442},

year  = {2009},

date = {2009-01-01},

journal = {SIAM Journal on Applied Mathematics},

volume = {70},

number = {3},

pages = {658--676},

publisher = {Society for Industrial and Applied Mathematics},

abstract = {A mixed formulation is proposed and analyzed mathematically for coupled convection-diffusion in heterogeneous medias. Transfer in solid parts driven by pure di?usion is coupled with convection-diffusion transfer in fluid parts. This study is carried out for translation-invariant geometries (general infinite cylinders) and unidirectional flows. This formulation brings to the fore a new convection-diffusion operator, the properties of which are mathematically studied: its symmetry is first shown using a suitable scalar product. It is proved to be self-adjoint with compact resolvent on a simple Hilbert space. Its spectrum is characterized as being composed of a double set of eigenvalues: one converging towards ?? and the other towards +?, thus resulting in a nonsectorial operator. The decomposition of the convection-di?usion problem into a generalized eigenvalue problem permits the reduction of the original three-dimensional problem into a two-dimensional one. Despite the operator being nonsectorial, a complete solution on the infinite cylinder, associated to a step change of the wall temperature at the origin, is exhibited with the help of the operator?s two sets of eigenvalues/eigenfunctions. On the computational point of view, a mixed variational formulation is naturally associated to the eigenvalue problem. Numerical illustrations are provided for axisymmetrical situations, the convergence of which is found to be consistent with the numerical discretization.},

note = {Thanks to SIAM editor. This publication is available at http://epubs.siam.org/siap/},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5468,

title = {Symmetry breaking and electrostatic attraction between two identical surfaces},

author = {Franck Plouraboué and Hsueh-Chia Chang},

url = {https://oatao.univ-toulouse.fr/5468/},

doi = {10.1103/PhysRevE.79.041404},

year  = {2009},

date = {2009-01-01},

urldate = {2009-01-01},

journal = {Physical Review E},

volume = {79},

number = {4},

pages = {041404(1)--041404(9)},

publisher = {American Physical Society},

abstract = {By allowing the surface charge of one surface to affect the adsorption equilibrium of the other, we establish 

the existence of a long-range attractive interaction between two identical surfaces in an electrolyte containing 

polyvalent counterions with a mean-field Poisson-Boltzmann approach. A Stern electrostatic condition from 

linearization of the mass-action adsorption isotherm is used to capture how polyvalent ion condensation affects and reverses the surface charge. We furthermore establish a direct mapping between this Stern-layer condition and previously derived modified mean-field formulations associated with correlated fluctuations theory. For a sufficiently potential-sensitive isotherm, antisymmetric charge inversion can occur to produce an attractive force that increases with decreasing ionic strengths. Analyses of a mass-action isotherm produce force-separation relations, including an exponential far-?eld force decay distinct but consistent with previously 

proposed correlated fluctuation theories and in quantitative agreement with experimental data.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{F2008,

title = {Attraction between two similar particles in an electrolyte: effects of Stern layer absorption},

author = {Plouraboué F, Chang HC},

url = {https://hal.archives-ouvertes.fr/file/index/docid/338932/filename/art_iutam.pdf},

doi = {10.1590/s0001-37652010000100009},

year  = {2008},

date = {2008-11-14},

journal = {An Acad Bras Cienc.},

volume = {82},

number = {1},

pages = {95-108},

abstract = {When Debye length is comparable or larger than the distance between two identical particles, the overlapping among the particles double-layers can play an important role in their interactions. This paper presents a theoretical analysis of the interaction among two identical particles with overlapped double-layers. We particularly focus on the effect of a Stern electro static condition from linearization of the adsorption isotherm near the isoelectric (neutrality) point in order to capture how polyvalent ion condensation affect sand reverses the surface charge. The stationary potential problem is solved within the framework of an asymptotic lubrication approach for a mean-field Poisson-Boltzmann model. Both spherical and cylindrical particles are analyzed. The results are finally discussed in the context of Debye-Hückel (D-H) limit and beyond it.},

note = {PMID: 20209246},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5470,

title = {Nonuniversal conductivity exponents in continuum percolating Gaussian fractures},

author = {Frédérique Flukiger and Franck Plouraboué and Marc Prat},

url = {https://oatao.univ-toulouse.fr/5470/},

doi = {10.1103/PhysRevE.77.047101},

year  = {2008},

date = {2008-01-01},

journal = {Physical Review E},

volume = {77},

number = {4},

pages = {047101--1-047101-4},

publisher = {The American Physical Society},

abstract = {We study the electrical and hydraulic conductivity percolation exponents in a Gaussian fracture using the method proposed in Plouraboué et al. [Phys. Rev. E 73, 036305, 2006]. Nonuniversal conductivity percolation exponents are found: they differ from the theoretical predictions for in?nite system size for frozen power-law distributions of local conductivities, as with their ?nite size corrections. In the hydraulic case, we also ?nd that the probability density function of the conductivity follows a power-law distribution near the percolation threshold.},

note = {Thanks to The American Physical Society. 

The definitive version is available at http://dx.doi.org/10.1103/PhysRevE.77.047101},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5469,

title = {Gap Filling of 3-D Microvascular Networks by Tensor Voting},

author = {Laurent Risser and Franck Plouraboué and Xavier Descombes},

url = {https://oatao.univ-toulouse.fr/5469/

https://ieeexplore.ieee.org/document/4389807},

doi = {10.1109/TMI.2007.913248},

year  = {2008},

date = {2008-01-01},

urldate = {2008-01-01},

journal = {IEEE Transactions on Medical Imaging},

volume = {27},

number = {5},

pages = {674--687},

publisher = {Institute of Electrical and Electronics Engineers},

abstract = {We present a new algorithm which merges discontinuities in 3-D images of tubular structures presenting undesirable gaps. The application of the proposed method is mainly associated to large 3-D images of microvascular networks. In order to recover the real network topology, we need to fill the gaps between the closest discontinuous vessels. The algorithm presented in this paper aims at achieving this goal. This algorithm is based on the skeletonization of the segmented network followed by a tensor voting method. It permits to merge the most common kinds of discontinuities found in microvascular networks. It is robust, easy to use, and relatively fast. The microvascular network images were obtained using synchrotron tomography imaging at the European Synchrotron Radiation Facility. These images exhibit samples of intracortical networks. Representative results are illustrated.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5472,

title = {Critical point network for drainage between rough surfaces},

author = {Olivier Amyot and Frédérique Flukiger and Sandrine Geoffroy and Franck Plouraboué and Marc Prat},

url = {https://oatao.univ-toulouse.fr/5472/},

doi = {10.1007/s11242-007-9098-3},

year  = {2007},

date = {2007-01-01},

urldate = {2007-01-01},

journal = {Transport in Porous Media},

volume = {70},

number = {2},

pages = {257--277},

publisher = {Springer},

abstract = {In this paper, we present a network method for computing two-phase flows between two rough surfaces with significant contact areas. Low-capillary number drainage is investigated here since one-phase flows have been previously investigated in other contributions. An invasion percolation algorithm is presented for modeling slow displacement of a wetting fluid by a non wetting one between two rough surfaces. Short-correlated Gaussian process is used to model random rough surfaces.The algorithm is based on a network description of the fracture aperture field. The network is constructed from the identification of critical points (saddles and maxima) of the aperture field. The invasion potential is determined from examining drainage process in a flat mini-channel. A direct comparison between numerical prediction and experimental visualizations on an identical geometry has been performed for one realization of an artificial fracture with a moderate fractional contact area of about 0.3. A good agreement is found between predictions and observations.},

note = {Thanks to Springer. The definitive version is available at http://www.springerlink.com. The original PDF of the article can be found at Transport in Porous Media website : http://www.springerlink.com/content/c088378t11p4880n/?MUD=MP},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5476,

title = {Capillary pinching in a pinched microchannel},

author = {Olivier Amyot and Franck Plouraboué},

url = {https://oatao.univ-toulouse.fr/5476/},

doi = {10.1063/1.2709704},

year  = {2007},

date = {2007-01-01},

journal = {Physics of Fluids},

volume = {19},

number = {3},

pages = {033101--1-033101-10},

publisher = {American Institute of Physics},

abstract = {We report a study of the capillary pinching of a gas bubble by a wetting liquid inside a pinched channel. The capillary pinching induces very reproducible bubbling, at a very well-de?ned frequency. There are two regimes associated with drip and jet bubbling. In the latter, we show that highly monodispersed bubbles are formed by our pinched channel. The dynamics of the bubble formation also shows two distinct regimes: a long-duration elongation of the air bubble and a rapid relaxation of the interface after interface breakup. The slow regime depends on the ?ux imposed and the channel geometry. The rapid deformation dynamic regime depends very weakly on the boundary conditions. Scaling arguments are proposed in the context of the lubrication approximation to describe the two regimes.},

note = {Thanks to American Institute of Physics editor. The definitive version is available at http://pof.aip.org/ The original PDF of the article can be found at Physics of Fluids website : http://pof.aip.org/resource/1/phfle6/v19/i3/p033101_s1},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5471,

title = {Stationary convection-diffusion between two co-axial cylinders},

author = {Franck Plouraboué and Charles Pierre},

url = {https://oatao.univ-toulouse.fr/5471/

http://www.sciencedirect.com/science/article/pii/S0017931007004772},

doi = {10.1016/j.ijheatmasstransfer.2007.06.037},

year  = {2007},

date = {2007-01-01},

urldate = {2007-01-01},

journal = {International Journal of Heat and Mass Transfer},

volume = {50},

number = {23-24},

pages = {4901--4907},

publisher = {Elsevier},

abstract = {In this note, we examine the high Peclet number limit of the stationary extended Graetz problem for which two families of real and imaginary eigenvalues are associated, respectively, with a downstream convective relaxation and the upstream diffusive establishment. The asymptotic behavior of both families of eigenvalues is studied, in the limit of large Peclet number and thin wall, which bring to the fore a single parameter dependence, previously mentioned in the literature from numerical investigations [M.A. Cotton, J.D. Jackson, in: R.W. Lewis, K. Morgan (Eds.), Numerical Methods in Thermal Problems, vol. IV, Pineridge Press, Swansea, 1985, pp. 504-515]. The fully developed region is specifically studied thanks to the first eigenvalue dependence on the Peclet number, on the thermal conductivity coefficients and on the diameter ratio of the cylinders. The effective transport between the fluid and the solid is investigated through the 

evaluation of the fully developed Nusselt number and experimental measurements.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5479,

title = {Quasi-static liquid-air drainage in narrow channels with variations in the gap},

author = {Sandrine Geoffroy and Franck Plouraboué and Marc Prat and Olivier Amyot},

url = {https://oatao.univ-toulouse.fr/5479/},

doi = {10.1016/j.jcis.2005.07.008},

year  = {2006},

date = {2006-02-01},

journal = {Journal of Colloid and Interface Science},

volume = {294},

number = {1},

pages = {165--175},

publisher = {Elsevier},

abstract = {This paper studies the shape of an air bubble quasi-statically flowing in the longitudinal direction of narrow channels. Two bottom topographies are treated, i.e., linear and quadratic variations of the gap along the transverse direction. This work analyses the main characteristics of the gas?liquid interface with respect to the wedge aspect ratio. From the convergence of asymptotic, numerical and experimental analyses, we found simple dependences for the finger width and total curvature as a function of channel aspect ratio. These results provide simple and general expressions for the pressure drop needed to overcome capillary forces and push the air finger inside the channel.},

note = {Thanks to Elsevier editor. The definitive version is available at http://www.sciencedirect.com The original PDF of the article can be found at Journal of Colloid and Interface Science website : http://www.sciencedirect.com/science/journal/00219797},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5473,

title = {Geodesic network method for flows between two rough surfaces in contact},

author = {Franck Plouraboué and Frédérique Flukiger and Marc Prat and Pierre Crispel},

url = {https://oatao.univ-toulouse.fr/5473/

http://pre.aps.org/abstract/PRE/v73/i3/e036305},

doi = {10.1103/PhysRevE.73.036305},

year  = {2006},

date = {2006-01-01},

urldate = {2006-01-01},

journal = {Physical Review E (PRE)},

volume = {73},

number = {3},

pages = {036305--1},

publisher = {American Physical Society},

abstract = {A discrete network method based on previous asymptotic analysis for computing fluid flows between confined rough surfaces is proposed. This random heterogeneous geodesic network method could be either applied to surfaces described by a continuous random field or finely discretized on a regular grid. This method tackles the difficult problem of fluid transport between rough surfaces in close contact. We describe the principle of the method as well as detail its numerical implementation and performances. Macroscopic conductances are computed and analyzed far from the geometrical percolation threshold. Numerical results are successfully compared with the effective medium approximation, the application of which is also studied analytically.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5477,

title = {From homogeneous to fractal normal and tumorous microvascular networks in the brain},

author = {Laurent Risser and Franck Plouraboué and Alexandre Steyer and Peter Cloetens and Géraldine Le Duc and Caroline Fonta},

url = {https://oatao.univ-toulouse.fr/5477/},

doi = {10.1038/sj.jcbfm.9600332},

year  = {2006},

date = {2006-01-01},

journal = {Journal of Cerebral Blood Flow and Metabolism},

volume = {27},

number = {2},

pages = {293--303},

publisher = {Nature Publishing Group},

abstract = {We studied normal and tumorous three-dimensional (3D) microvascular networks in primate and rat brain. Tissues were prepared following a new preparation technique intended for high-resolution synchrotron tomography of microvascular networks. The resulting 3D images with a spatial resolution of less than the minimum capillary diameter permit a complete description of the entire vascular network for volumes as large as tens of cubic millimeters. The structural properties of the vascular networks were investigated by several multiscale methods such as fractal and power-spectrum analysis. These investigations gave a new coherent picture of normal and pathological complex vascular structures. They showed that normal cortical vascular networks have scale-invariant fractal properties on a small scale from 1.4 lm up to 40 to 65 lm. Above this threshold, vascular networks can be considered as homogeneous. Tumor vascular networks show similar characteristics, but the validity range of the fractal regime extend to much larger spatial dimensions. 

These 3D results shed new light on previous two dimensional analyses giving for the first time a 

direct measurement of vascular modules associated with vessel-tissue surface exchange.},

note = {Thanks to Nature Publishing group. This article is available at http://www.nature.com/jcbfm/index.html},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5480,

title = {Weak-inertial flow between two rough surfaces},

author = {David Lo Jacono and Franck Plouraboué and Alain Bergeon},

url = {https://aip.scitation.org/doi/full/10.1063/1.1923347

https://oatao.univ-toulouse.fr/5480/},

doi = {10.1063/1.1923347},

year  = {2005},

date = {2005-05-01},

urldate = {2005-05-01},

journal = {Physics of Fluids},

volume = {17},

number = {6},

pages = {063602--1-033101-10},

publisher = {American Institute of Physics},

abstract = {Oseen-Poiseuille equations are developed from an asymptotic formulation of the three-dimensional Navier-Stokes equations in order to study the influence of weak inertia on flows between rough surfaces. The impact of the first correction on macroscopic flow due to inertia has been determined by solving these equations numerically. From the numerical convergence of the asymptotic expansion to the three-dimensional Navier?Stokes flows, it is shown that, at the macroscopic scale, the quadratic correction to the Reynolds equation in the weak-inertial regime vanishes generalizing a similar result in porous media.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5489,

title = {Kelvin-Helmholtz instability in a Hele-Shaw cell: Large effect from the small region near the meniscus},

author = {E. John Hinch and Franck Plouraboué},

url = {https://oatao.univ-toulouse.fr/5489/},

doi = {10.1063/1.1914729},

year  = {2005},

date = {2005-01-01},

urldate = {2005-01-01},

journal = {Physics of Fluids},

volume = {17},

number = {5},

pages = {052107(1)--052107(13)},

publisher = {American Institute of Physics},

abstract = {In an attempt to improve the poor prediction of our previous theory, we examine corrections from the small region in a Hele-Shaw cell near the meniscus where the flow is three dimensional. At larger Reynolds numbers, we find an O(1) change to the effective boundary condition for mass conservation which is to be applied to the large scale flow outside the small region.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5482,

title = {Convergence of the Generalized Volume Averaging Method on a Convection-Diffusion Problem: A Spectral Perspective},

author = {Charles Pierre and Franck Plouraboué and Michel Quintard},

url = {https://oatao.univ-toulouse.fr/5482/

https://epubs.siam.org/doi/10.1137/040610015},

doi = {10.1137/040610015},

year  = {2005},

date = {2005-01-01},

urldate = {2005-01-01},

journal = {SIAM Journal on Applied Mathematics},

volume = {66},

number = {1},

pages = {122--152},

publisher = {Society for Industrial and Applied Mathematics},

abstract = {A mixed formulation is proposed and analyzed mathematically for coupled convection-diffusion in heterogeneous medias. Transfer in solid parts driven by pure diffusion is coupled with convection-diffusion transfer in fluid parts. This study is carried out for translation-invariant geometries (general infinite cylinders) and unidirectional flows. This formulation brings to the fore a new convection-diffusion operator, the properties of which are mathematically studied: its symmetry is first shown using a suitable scalar product. It is proved to be self-adjoint with compact resolvent on a simple Hilbert space. Its spectrum is characterized as being composed of a double set of eigenvalues: one converging towards -∞ and the other towards +∞, thus resulting in a nonsectorial operator. The decomposition of the convection-diffusion problem into a generalized eigenvalue problem permits the reduction of the original three-dimensional problem into a two-dimensional one. Despite the operator being nonsectorial, a complete solution on the in?nite cylinder, associated to a step change of the wall temperature at the origin, is exhibited with the help of the operator's two sets of eigenvalues/eigenfunctions. On the computational point of view, a mixed variational formulation is naturally associated to the eigenvalue problem. Numerical illustrations are provided for axisymmetrical situations, the convergence of which is found to be consistent with the numerical discretization.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5483,

title = {X-ray high-resolution vascular network imaging},

author = {Franck Plouraboué and Peter Cloetens and Caroline Fonta and Alexandre Steyer and Frédéric Lauwers and J. P Marc-Vergnes},

url = {https://oatao.univ-toulouse.fr/5483/},

doi = {10.1111/j.0022-2720.2004.01362.x},

year  = {2004},

date = {2004-08-01},

urldate = {2004-08-01},

journal = {Journal of Microscopy},

volume = {215},

number = {2},

pages = {139--148},

publisher = {Wiley},

abstract = {This paper presents the first application of high-resolution X-ray synchrotron tomography to the imaging of large micro-vascular networks in biological tissue samples. This technique offers the opportunity of analysing the full three-dimensional vascular network from the micrometre to the millimetre scale. 

This paper presents the specific sample preparation method and the X-ray imaging procedure. Either barium or iron was injected as contrast agent in the vascular network. The impact of the composition and concentration of the injected solution on the X-ray synchrotron tomography images has been studied. Two imaging modes, attenuation and phase contrast, are compared. Synchrotron high-resolution computed tomography offers new prospects in the three-dimensional imaging of in situ biological vascular networks.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5484,

title = {Conductances between confined rough walls},

author = {Franck Plouraboué and Sandrine Geoffroy and Marc Prat},

url = {https://aip.scitation.org/doi/abs/10.1063/1.1644152

https://oatao.univ-toulouse.fr/5484/},

doi = {10.1063/1.1644152},

year  = {2004},

date = {2004-03-01},

urldate = {2004-03-01},

journal = {Physics of Fluids},

volume = {16},

number = {3},

pages = {615--624},

publisher = {American Institute of Physics},

abstract = {Two- and three-dimensional creeping flows and diffusion transport through constricted and possibly rough surfaces are studied. Asymptotic expansions of conductances are derived as functions of the constriction local geometry. The validity range of the proposed theoretical approximations is explored through a comparison either with available exact results for specific two-dimensional aperture fields or with direct numerical computations for general three-dimensional geometries. The large validity range of the analytical expressions proposed for the hydraulic conductivity (and to a lesser extent for the electrical conductivity) opens up interesting perspectives for the simulation of flows in highly complicated geometries with a large number of constrictions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5485,

title = {Un nouveau préconditionneur pour les problèmes elliptiques à coefficients variables},

author = {Mejdi Aza{"i}ez and Alain Bergeon and Franck Plouraboué},

url = {https://oatao.univ-toulouse.fr/5485/},

doi = {10.1016/S1631-0721(03)00091-3},

year  = {2003},

date = {2003-07-01},

journal = {Comptes Rendus Mécanique},

volume = {331},

number = {7},

pages = {509--514},

publisher = {Elsevier},

abstract = {On présente dans cette Note un nouveau préconditionneur pour l?inversion du syst`eme algébrique issu de la discrétisation par méthode spectrale d?un probl`eme elliptique du second ordre `a coefficients variables et non séparables. Ce préconditionneur est construit en discrétisant un probl`eme similaire `a l?original et obtenu par moyenne des coefficients. L?inversion du préconditionneur utilise une méthode directe connue sous le nom de diagonalisation successive.},

note = {Thanks to Elsevier editor. The definitive version is available at http://www.sciencedirect.com. The original PDF of the article can be found at Comptes Rendus Mécanique website : http://www.sciencedirect.com/science/article/pii/S1631072103000913},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5487,

title = {Average Flow Model of Rough Surface Lubrication: Flow Factors for Sinusoidal Surfaces},

author = {Nicolas Letalleur and Franck Plouraboué and Marc Prat},

url = {http://dx.doi.org/10.1115/1.1467084

https://oatao.univ-toulouse.fr/5487/},

doi = {10.1115/1.1467084},

year  = {2002},

date = {2002-07-01},

urldate = {2002-07-01},

journal = {Journal of Tribology},

volume = {124},

number = {3},

pages = {539--546},

publisher = {American Society of Mechanical Engineers (ASME)},

abstract = {The effects of lubricant film flow, pressurized and sheared between two parallel sinusoidal wavy surfaces in sliding motion is studied analytically. Results are presented using a flow factor model which provides an average description of the surfaces roughness impact. Two distinct cases are studied in order to compare stationary or time dependent local aperture configurations. Flow factors are computed respectively for each case through spatial or spatio-temporal average, revealing striking differences. The results shed light on the relevance of the composite roughness concept. Special attention is paid to the flow factor analytical behavior when surfaces are near contact.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5481,

title = {Kelvin-Helmholtz instability in a Hele-Shaw cell},

author = {Franck Plouraboué and E. John Hinch},

url = {https://oatao.univ-toulouse.fr/5481/},

doi = {10.1063/1.1446884},

year  = {2002},

date = {2002-03-01},

urldate = {2002-03-01},

journal = {Physics of Fluids},

volume = {14},

number = {3},

pages = {922--929},

publisher = {American Institute of Physics},

abstract = {A linear stability analysis is presented for the Kelvin-Helmholtz instability in a Hele-Shaw cell, an analysis based on the Navier-Stokes equation to improve on the previous Euler-Darcy study that Gondret and Rabaud [Phys. Fluids 9, 3267 (1997)] made of their own experiments.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5486,

title = {Averaged Reynolds Equation for Flows between Rough Surfaces in Sliding Motion},

author = {Marc Prat and Franck Plouraboué and Nicolas Letalleur},

url = {https://oatao.univ-toulouse.fr/5486/},

doi = {10.1023/A:1015772525610},

year  = {2002},

date = {2002-01-01},

journal = {Transport in Porous Media},

volume = {48},

number = {3},

pages = {291--313},

publisher = {Springer},

abstract = {The ?ow between rough surfaces in sliding motion with contacts between these surfaces, 

is analyzed through the volume averaging method. Assuming a Reynolds (lubrication) approximation 

at the roughness scale, an average ?ow model is obtained combining spatial and time average. Time 

average, which is often omitted in previous works, is specially discussed. It is shown that the effective 

transport coef?cients, traditionally termed ??ow factors? in the lubrication literature, that appear in 

the average equations can be obtained from the solution to two closure problems. This allows for the 

numerical determination of ?ow factors on ?rmer bases and sheds light on some arguments to the 

literature. Moreover, ?uid ?ows through fractures form an important subset of problems embodied 

in the present analysis, for which macroscopisation is given.},

note = {Thanks to Springer. The original publication is available at www.springerlink.com},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5495,

title = {Light scattering from cold rolled aluminum surfaces},

author = {Damien Vandembroucq and Annie Tarrats and Jean-Jacques Greffet and Stéphane Roux and Franck Plouraboué},

url = {http://www.sciencedirect.com/science/journal/00304018

https://oatao.univ-toulouse.fr/5495/},

doi = {10.1016/S0030-4018(00)01136-6},

year  = {2001},

date = {2001-01-01},

urldate = {2001-01-01},

journal = {Optics Communications},

volume = {187},

number = {4-6},

pages = {289--294},

publisher = {Elsevier},

abstract = {We present experimental light scattering measurements from aluminum surfaces obtained by cold rolling. We show that our results are consistent with a scale invariant description of the roughness of these surfaces. The roughness parameters that we obtain from the light scattering experiment are consistent with those obtained from atomic force microscopy measurements.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5491,

title = {Generalized Lagrangian Coordinates for Transport and Two-Phase Flows in Heterogeneous Anisotropic Porous Media},

author = {Franck Plouraboué and Alain Bergeon and Mejdi Azaïez},

url = {https://oatao.univ-toulouse.fr/5491/},

doi = {10.1023/A:1010786423656},

year  = {2001},

date = {2001-01-01},

urldate = {2001-01-01},

journal = {Transport in Porous Media},

volume = {44},

number = {2},

pages = {281--304},

publisher = {Springer},

abstract = {We show how Lagrangian coordinates provide an effective representation of how difficult non-linear, hyperbolic transport problems in porous media can be dealt with. Recalling Lagrangian description first, we then derive some basic but remarkable properties useful for the numerical computation of projected transport operators. We furthermore introduce new generalized Lagrangian coordinates with their application to the Darcy-Muskat two-phase flow models. We show how these generalized Lagrangian coordinates can be constructed from the global mass conservation, and that they are related to the existence of a global pressure previously de?ned in the literature about the subject. The whole representation is developed in two or three dimensions for numerical purposes, for isotropic or anisotropic heterogeneous porous media.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5492,

title = {Sliding lubricated anisotropic rough surfaces},

author = {Franck Plouraboué and Marc Prat and Nicolas Letalleur},

url = {https://journals.aps.org/pre/abstract/10.1103/PhysRevE.64.011202

https://oatao.univ-toulouse.fr/5492/},

doi = {10.1103/PhysRevE.64.011202},

year  = {2001},

date = {2001-01-01},

urldate = {2001-01-01},

journal = {Physical Review E},

volume = {64},

number = {1},

pages = {011202(1)--011202(10)},

publisher = {American Physical Society},

abstract = {The object of this paper is to study the effects of lubricant film flow, pressurized and sheared between two parallel rough surfaces in sliding motion. The influence of microscopic surface roughness on lubricant film flow macroscopic behavior is described through five nondimensional parameters called flow factors. These macroscopic transport parameters are related to the local geometry of apertures and surfaces. Short- and long-range-correlated surface roughnesses display very different macroscopic behaviors when surfaces are close to contact. These behaviors are related to underlying surface roughness parameters such as the correlation length and the self-affine Hurst exponent. The problem is numerically studied, and results are compared to some analytical asymptotic results.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5496,

title = {Experimental study of the transport properties of rough self-affine fractures},

author = {Franck Plouraboué and Pascal Kurowski and Jean-Marc Boffa and Jean-Pierre Hulin and Stéphane Roux},

url = {https://doi.org/10.1016/S0169-7722(00)00134-0

https://oatao.univ-toulouse.fr/5496/},

doi = {10.1016/S0169-7722(00)00134-0},

year  = {2000},

date = {2000-01-01},

urldate = {2000-01-01},

journal = {Journal of Contaminant Hydrology},

volume = {46},

number = {3-4},

pages = {295--318},

publisher = {Elsevier},

abstract = {An experimental study of the transport properties of fluid-saturated joints composed of two complementary rough fracture surfaces, translated with respect to each other and brought in contact, is reported. Quantitative roughness measurements on different fractured granite samples show that the surfaces have a self-affine geometry from which the dependence of the mean aperture on the relative displacement of fracture surfaces kept in contact can be predicted. Variations of the hydraulic and electrical conductances of the joint are measured as functions of its mean aperture. A simple parallel plane model accounts for the global trend of the measurements, but significant deviations are observed when a relative lateral displacement of the surfaces is introduced. A theoretical analysis of their origin shows that they are due both to the randomness of the aperture field and to a nonzero local slope of the surface near the injection hole; the corresponding conductivity fluctuation amplitudes have power law and linear variations with the lateral displacement, and are enhanced by the radial injection geometry.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5497,

title = {Roughness of sandstone fracture surfaces: Profilometry and shadow length investigations},

author = {Jean-Marc Boffa and C. Allain and R. Chertcoff and Jean-Pierre Hulin and Franck Plouraboué and Stéphane Roux},

url = {https://oatao.univ-toulouse.fr/5497/},

doi = {10.1007/s100510050602},

year  = {1999},

date = {1999-01-01},

urldate = {1999-01-01},

journal = {The European Physical Journal B},

volume = {7},

number = {2},

pages = {179--182},

publisher = {Springer},

abstract = {The geometrical properties of fractured sandstone surfaces were studied by measuring the length distribution of the shadows appearing under grazing illumination. Three distinct domains of variation were found: at short length scales a cut-off of self-affinity is observed due to the inter-granular rupture of sandstones, at long length scales, the number of shadows falls off very rapidly because of the non-zero illumination angle and of the finite roughness amplitude. Finally, in the intermediate domain, the shadow length distribution displays a power law decrease with an exponent related to the roughness exponent measured by mechanical profilometry. Moreover, this method is found to be more sensitive to deviations from self-affinity than usual methods.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5498,

title = {Multi-scale roughness transfer in cold metal rolling},

author = {Franck Plouraboué and Matthieu Boehm},

url = {http://dx.doi.org/10.1016/S0301-679X(99)00013-4

https://oatao.univ-toulouse.fr/5498/},

doi = {10.1016/S0301-679X(99)00013-4},

year  = {1999},

date = {1999-01-01},

urldate = {1999-01-01},

journal = {Tribology International},

volume = {32},

number = {1},

pages = {45--57},

publisher = {Elsevier},

abstract = {We report on a comparative Atomic Force Microscope (AFM) multi-scale roughness analysis of cold rolled Al alloy and steel roll, in order to characterize the roughness transfer from the steel roll to the workpiece in cold strip rolling processes. More than three orders of length-scale magnitudes were investigated from 100 μ to 50 nm on both types of surfaces. The analysis reveals that both types of surfaces are anisotropic self-affine surfaces. Transverse and longitudinal height profiles exhibit a different roughness exponent (Hurst exponent) ζ⊥=0.93±0.03 and ζ⊥=0.5±$0.05 Different length-scale cut-offs are obtained in each direction lsup=50mm, lsup>100mm. Height and slope distributions are also computed to complement this study. The above mentionned self-affine characteresitics are found to be very similar for the roll and the strip surfaces, which suggest that roughness transfer takes place from the macroscopic (100 μm) to the very small scale (50 nm).},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5499,

title = {Un nouveau système de coordonnées pour les équations de Darcy-Muskat diphasiques en milieux poreux hétérogènes isotropes à deux dimensions},

author = {Franck Plouraboué},

url = {https://oatao.univ-toulouse.fr/5499/},

doi = {10.1016/S1251-8069(99)80035-0},

year  = {1998},

date = {1998-01-01},

journal = {Comptes Rendus de l'Académie des Sciences - Series IIB - Mechanics-Physics-Astronomy},

volume = {326},

number = {12},

pages = {827--832},

publisher = {Elsevier},

abstract = {Nous formulons les équations Darcy-Muskat pour les écoulements diphasiques en milieu poreux hétérogène `a l'aide d'équations non linéaires couplées entre la saturation et la fonction de courant globale (ou la pression globale). A deux dimensions, le système de coordonnées associé `a la fonction de courant globale et la pression globale monophasique équivalente dans la limite des nombres capillaires infinis permet de dire l'évolution de la saturation des phases comme unidimensionnelle. Nous montrons comment ce système de coordonnées permet à grand nombre capillaires, la mise en œuvre d'une méthode de calcul numérique performante, pour le problème diphasique complet.},

note = {Thanks to Elsevier publ. The original PDF is available at http://www.sciencedirect.com/science/journal/12874620},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5500,

title = {Numerical study of geometrical dispersion in self-affine rough fractures},

author = {Franck Plouraboué and Jean-Pierre Hulin and Stéphane Roux and Joel Koplik},

url = {https://oatao.univ-toulouse.fr/5500/},

doi = {10.1103/PhysRevE.58.3334},

year  = {1998},

date = {1998-01-01},

journal = {Physical Review E},

volume = {58},

number = {3},

pages = {3334--3346},

publisher = {American Physical Society},

abstract = {We report a numerical study of passive tracer dispersion in fractures with rough walls modeled as the space between two complementary self-affine surfaces rigidly translated with respect to each other. Geometrical dispersion due to the disorder of the velocity distribution is computed using the lubrication approximation. Using a spectral perturbative scheme to solve the flow problem and a mapping coordinate method to compute dispersion, we perform extensive ensemble averaged simulations to test theoretical predictions on the dispersion dependence on simple geometrical parameters. We observe the expected quadratic dispersion coefficient dependence on both the mean aperture and the relative shift of the crack as of well as the anomalous dispersion dependence on tracer traveling distance. We also characterize the anisotropy of the dispersion front, which progressively wrinkles into a self-af?ne curve whose exponent is equal to that of the fracture surface.},

note = {Thanks to APS editor. The original PDF is available at http://pre.aps.org/},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5501,

title = {Tracer Dispersion in Rough Open Cracks},

author = {Stéphane Roux and Franck Plouraboué and Jean-Pierre Hulin},

url = {https://oatao.univ-toulouse.fr/5501/},

doi = {10.1023/A:1006553902753},

year  = {1998},

date = {1998-01-01},

urldate = {1998-01-01},

journal = {Transport in Porous Media},

volume = {32},

number = {1},

pages = {97--116},

publisher = {Springer},

abstract = {Tracer dispersion is studied in an open crack where the two rough crack faces have been translated with respect to each other. The different dispersion regimes encountered in rough-wall Hele-Shaw cell are first introduced, and the geometric dispersion regime in the case of self-affine crack surfaces is treated in detail through perturbation analysis. It is shown that a line of tracer is progressively wrinkled into a self-affine curve with an exponent equal to that of the crack surface. This leads to a global dispersion coefficient which depends on the distance from the tracer inlet, but which is still proportional to the mean advection velocity. Besides, the tracer front is subjected to a local dispersion (as could be revealed by point measurements or echo experiments) very different from the global one. The expression of this anomalous local dispersion coefficient is also obtained.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5503,

title = {Experimental study of the roughness of crumpled surfaces},

author = {Franck Plouraboué and Stéphane Roux},

url = {http://dx.doi.org/10.1016/0378-4371(95)00380-0

https://oatao.univ-toulouse.fr/5503/},

doi = {10.1016/0378-4371(95)00380-0},

year  = {1996},

date = {1996-06-01},

urldate = {1996-06-01},

journal = {Physica A Statistical Mechanics and its Applications},

volume = {227},

number = {3-4},

pages = {173--182},

publisher = {Elsevier},

abstract = {We report on the experimental study of the roughness of randomly crumpled surfaces which are unfolded. This system provides a natural example of random surfaces which exhibit long-range correlations. It is shown that such rough surfaces are self-affine with a Hurst exponent H textttchar126 0.9. A simple one-dimensional model illustrates the way long-range correlations may naturally occur in the crumpling process.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5504,

title = {Experimental study of fracture surface roughness on rocks with crack velocity},

author = {Franck Plouraboué and Kenneth Winkler and Luc Petitjean and Jean-Pierre Hulin and Stéphane Roux},

url = {https://oatao.univ-toulouse.fr/5504/

http://pre.aps.org/abstract/PRE/v53/i1/p277_1},

doi = {PhysRevE.53.277},

year  = {1996},

date = {1996-01-01},

urldate = {1996-01-01},

journal = {Physical Review E},

volume = {53},

number = {1},

pages = {277--283},

publisher = {American Physical Society},

abstract = {In this paper we address the question of the influence of crack velocity on the fractured surface roughness. We studied samples made of Berea sandstone, chosen for their good macroscopic homogeneity and their granular microstructure. The samples were fractured in a double cantilever geometry, which allowed for a controlled crack speed that was maintained constant for each sample using an imposed displacement quadratic in time. The range of speed covered in the experiments was 5.10-4 m/s to 2.10-1 m/s. Systematic profilometry measurements of the fractured surfaces revealed a self-affine geometry characterized by a roughness exponent, which was found to be independent of the crack speed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5502,

title = {Fluctuation dynamics of a single magnetic chain},

author = {Adriana S. Silva and Robert Bond and Franck Plouraboué and Denis Wirtz},

url = {https://oatao.univ-toulouse.fr/5502/},

doi = {10.1103/PhysRevE.54.5502},

year  = {1996},

date = {1996-01-01},

urldate = {1996-01-01},

journal = {Physical Review E},

volume = {54},

number = {5},

pages = {5502--5510},

publisher = {American Physical Society},

abstract = {"Tunable" fluids such as magnetorheological "MR" and electrorheological "ER" fluids are comprised of paramagnetic or dielectric particles suspended in a low-viscosity liquid. Upon the application of a magnetic or electric field, these fluids display a dramatic, reversible, and rapid increase of the viscosity. This change in viscosity can, in fact, be tuned by varying the applied field, hence the name "tunable fluids". This effect is due to longitudinal aggregation of the particles into chains in the direction of the applied field and the subsequent lateral aggregation into larger semisolid domains. A recent theoretical model by Halsey and Toor "HT" explains chain aggregation in dipolar fluids by a fluctuation-mediated long-range interaction between chains and predicts that this interaction will be equally efficient at all applied fields. This paper describes video-microscopy observations of long, isolated magnetic chains that test HT theory. The measurements show that, in contrast to the HT theory, chain aggregation occurs more efficiently at higher magnetic field strength (H0) and that this efficiency scales as H0?. Our experiments also yield the steady-state and time-dependent ?uctuation spectra C(x,x')? [h(x)-h(x')]?ensuremath>? and C(x,x',t,t')? ensuremath<[h(x,t)-h(x',t')]? ensuremath>? for the instantaneous deviation h(x,t) from an axis parallel to the ?eld direction to a point x on the chain. Results show that the steady-state ?uctuation growth is similar to a biased random walk with respect to the interspacing ? ensuremath|x-x'ensuremath| along the chain, C(x,x')$approx$ensuremath|x-x'ensuremath| ensuremathalpha, with a roughness exponent ensuremathalpha =0.53$pm$0.02. This result is partially confirmed by Monte Carlo simulations. Time-dependent results also show that chain relaxation is slowed down with respect to classical Brownian diffusion due to the magnetic chain connectivity, C(x,x',t,t')$approx$ensuremath|t-t'ensuremath|ensuremathbeta, with a growth exponent ensuremathbeta=0.35$pm$0.05ensuremath
keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao5505,

title = {Aperture of rough cracks},

author = {Franck Plouraboué and Pascal Kurowski and Jean-Pierre Hulin and Stéphane Roux and Jean Schmittbuhl},

url = {http://dx.doi.org/10.1103/PhysRevE.51.1675

https://oatao.univ-toulouse.fr/5505/},

doi = {10.1103/PhysRevE.51.1675},

year  = {1995},

date = {1995-03-01},

urldate = {1995-03-01},

journal = {Physical Review E},

volume = {51},

number = {3},

pages = {1675--1685},

publisher = {The American Physical Society},

abstract = {We analyse the problem of the geometrical aperture between the two faces of a crack described as a self-affine surface. We consider the contact of the two surfaces after a relative rigid-body displacement (translation and/or rotation) of one side of the crack with respect to the opposite one. A number of properties are obtained analytically and illustrated by numerical simulations on generated self-affine surfaces. The results concern the scaling of the average aperture which is shown to include a very slowly varying correction term (logarithmic with respect to the displacement) : this affects severely the dependence of the measured aperture on the displacement. These results are used to analyse experimental data obtained on a granite sample and to estimate the roughness exponent from a global measurement. This estimate is shown to agree with an analysis of the roughness based on profilometry measurements.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{oatao11898,

title = {Geometry of contact between self-affine surfaces},

author = {Franck Plouraboué and Stéphane Roux and Jean Schmittbuhl and Jean-Pierre Vilotte},

url = {https://oatao.univ-toulouse.fr/11898/},

doi = {10.1142/S0218348X95000114},

year  = {1995},

date = {1995-01-01},

urldate = {1995-01-01},

journal = {Fractals},

volume = {3},

number = {1},

pages = {113--122},

publisher = {Word scientific publishing},

abstract = {We study the geometry of the contact between two rigid self-affine surfaces. We investigate the mean shape of the surface in the vicinity of the contact point as well as the probability distribution of apertures a as a function of the distance to the contact point. The latter reveals two distinct scaling regimes which are characterized. We show that as the two surfaces are shifted with respect to each other, the contact point on one surface undergoes a "Levy walk". If u is the relative shift of the surfaces, the distance d between the two contact points (before and after the shift), scales as d ? u  alpha where the exponent ensuremathalpha is shown to be equal to the roughness exponent of the surfaces.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}