{"id":272,"date":"2021-07-21T08:36:40","date_gmt":"2021-07-21T08:36:40","guid":{"rendered":"https:\/\/franckplouraboue.net\/?page_id=272"},"modified":"2021-08-26T15:52:43","modified_gmt":"2021-08-26T15:52:43","slug":"bio-fluids","status":"publish","type":"page","link":"https:\/\/franckplouraboue.net\/?page_id=272","title":{"rendered":"Bio-fluids"},"content":{"rendered":"\t\t
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\n\t\t\t\t\t\t\t\t\t\"\"The study of biofluids is an active multi-disciplinary field of research involving soft matter and statistical physics, fluid mechanics and microfluidics. We are interested in <\/span>hydrodynamic modeling of spermatozoa cells <\/b>either at the individual or collective levels. Nevertheless, since beating cilia are generic from unicellular cells up to complex multicellular organisms, most of the developed models are relevant to a broader context.<\/span>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t
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\n\t\t\t\t\t\t\t\t\tHow active forces acting on flagella or cilia can be modeled? Combining models with observations of flagella\/cilia beating kinematics, is it possible to identify and evaluate these forces? How collective interactions are driving the transition from random to organized collective motion? How the observed collective behavior depends on cell concentration and how steric interactions can influence orientational order in dense packing?\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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\n\t\t\t\t\t\t\t\t\tWe analyzed the individual beating of spermatozoa both using original automatic segmentation tools (Yang et al, 2014<\/a>) and <\/span>bead models <\/span>(Delmotte et al, 2015<\/a>). The interest of
bead modelsBead models are articulated spheres or ellipsoids used to model flexible filaments subjected to various forces (including Brownian forcing) within a fluid.
They are widely used in polymer modeling.<\/span><\/div> resides in their ability to consider possibly complex mechanical anchoring conditions and\/or assemblies of cilia. Furthermore, we have shown that measuring the beating kinematics of cilia do not permit the identification and evaluation of the underlying active forcing (even for time-periodic ones) except when two independent measurements performed within two distinct and independent external flows are performed (Plourabou\u00e9 et al, 2017<\/a>). Regarding collective effects, we numerically analyzed the effect of long-range hydrodynamic interactions of a large number of active swimmers (pushers or pullers) leading to orientational order (Delmotte et al, 2015<\/a>, Delmotte et al., 2018<\/a>). \n
We also experimentally analyzed the random motion of dense ram semen, showing similarities with 2D turbulence in confined parallel Hele-Shaw cells (Creppy et al, 2015<\/a>). When confined within an annulus, such concentrated semen displays spontaneous rotation, the existence of which has been linked with steric interactions among cells as well as long-range orientational order (Creppy et al, 2016<\/a>).<\/span>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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2019<\/h3>

Sulaiman, Mostafa; Climent, \u00c9ric; Delmotte, Blaise; Fede, Pascal; Plourabou\u00e9, Franck; Verhille, Gautier<\/p>

Numerical modelling of long flexible fibers in homogeneous isotropic turbulence<\/a> Journal Article<\/span> <\/p>

In: <\/span>European Physical Journal E, <\/span>vol. 42, <\/span>no. 132, <\/span>2019<\/span>.<\/p>

Abstract<\/a><\/span> | Links<\/a><\/span> | BibTeX<\/a><\/span><\/p>

@article{oatao25639,
\r\ntitle = {Numerical modelling of long flexible fibers in homogeneous isotropic turbulence},
\r\nauthor = {Mostafa Sulaiman and {\u00c9}ric Climent and Blaise Delmotte and Pascal Fede and Franck Plourabou\u00e9 and Gautier Verhille},
\r\nurl = {https:\/\/oatao.univ-toulouse.fr\/25639\/},
\r\ndoi = {10.1140\/epje\/i2019-11894-7},
\r\nyear  = {2019},
\r\ndate = {2019-10-01},
\r\njournal = {European Physical Journal E},
\r\nvolume = {42},
\r\nnumber = {132},
\r\npublisher = {EDP Sciences},
\r\nabstract = {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, 
\r\n074501 (2014)) validating the assumptions of our model for the configurations we investigated.},
\r\nkeywords = {},
\r\npubstate = {published},
\r\ntppubtype = {article}
\r\n}
\r\n<\/pre><\/div>
Close<\/a><\/p><\/div>
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, 
\r\n074501 (2014)) validating the assumptions of our model for the configurations we investigated.<\/div>
Close<\/a><\/p><\/div>