Profile blunting and flow blockage in a yield-stress fluid: A molecular dynamics study

@article{citeulike:2878302, abstract = {The flow of a simple glass forming system (a 80:20 binary Lennard-Jones mixture) through a planar channel is studied via molecular dynamics simulations. The flow is driven by an external body force similar to gravity. Previous studies show that the model exhibits both a static [F. Varnik et al., J. Chem. Phys. 120, 2788 (2004)] and a dynamic [F. Varnik and O. Henrich, Phys. Rev. B 73, 174209 (2006)] yield stress in the glassy phase. These observations are corroborated by the present work, where we investigate how the presence of a yield stress may affect the system behavior in a Poiseuille-type flow geometry. In particular, we observe a blunted velocity profile across the channel: A relatively wide region in the channel center flows with a constant velocity (zero shear rate) followed by a nonlinear change of the shear rate as the walls are approached. The observed velocity gradients are compared to those obtained from the knowledge of the shear stress across the channel and the flow curves (stress versus shear rate), the latter being determined in our previous simulations of homogeneous shear flow. Furthermore, using the value of the (dynamic) yield stress known from previous simulations, we estimate the threshold body force for a complete arrest of the flow. Indeed, a blockage is observed as the imposed force falls below this threshold value. Small but finite shear rates are observed at stresses above the dynamic but below the static yield stress. We discuss the possible role of the stick-slip-like motion for this observation.}, author = {Varnik, F. and Raabe, D. }, citeulike-article-id = {2878302}, doi = {10.1103/PhysRevE.77.011504}, journal = {Physical Review E (Statistical, Nonlinear, and Soft Matter Physics)}, keywords = {2008, flow, grains, pre, qualif2, shear, shearband, simulation}, number = {1}, posted-at = {2008-06-09 23:45:40}, priority = {2}, publisher = {APS}, title = {Profile blunting and flow blockage in a yield-stress fluid: A molecular dynamics study}, url = {http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal\&id=PLEEE8000077000001011504000001\&idtype=cvips\&gifs=yes}, volume = {77}, year = {2008} }

TY - JOUR ID - citeulike:2878302 L3 - citeulike-article-id:2878302 TI - Profile blunting and flow blockage in a yield-stress fluid: A molecular dynamics study JF - Physical Review E (Statistical, Nonlinear, and Soft Matter Physics) VL - 77 IS - 1 PB - APS N2 - The flow of a simple glass forming system (a 80:20 binary Lennard-Jones mixture) through a planar channel is studied via molecular dynamics simulations. The flow is driven by an external body force similar to gravity. Previous studies show that the model exhibits both a static [F. Varnik et al., J. Chem. Phys. 120, 2788 (2004)] and a dynamic [F. Varnik and O. Henrich, Phys. Rev. B 73, 174209 (2006)] yield stress in the glassy phase. These observations are corroborated by the present work, where we investigate how the presence of a yield stress may affect the system behavior in a Poiseuille-type flow geometry. In particular, we observe a blunted velocity profile across the channel: A relatively wide region in the channel center flows with a constant velocity (zero shear rate) followed by a nonlinear change of the shear rate as the walls are approached. The observed velocity gradients are compared to those obtained from the knowledge of the shear stress across the channel and the flow curves (stress versus shear rate), the latter being determined in our previous simulations of homogeneous shear flow. Furthermore, using the value of the (dynamic) yield stress known from previous simulations, we estimate the threshold body force for a complete arrest of the flow. Indeed, a blockage is observed as the imposed force falls below this threshold value. Small but finite shear rates are observed at stresses above the dynamic but below the static yield stress. We discuss the possible role of the stick-slip-like motion for this observation. KW - 2008 KW - flow KW - grains KW - pre KW - qualif2 KW - shear KW - shearband KW - simulation AU - Varnik, F AU - Raabe, D PY - 2008/// UR - http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PLEEE8000077000001011504000001&idtype=cvips&gifs=yes ER -