Kabacaoğlu G, Quaife B, Biros G
Department of Mechanical Engineering, The University of Texas at Austin , Austin, Texas 78712, USA.
Department of Scientific Computing, Florida State University , Tallahassee, Florida 32306, USA.
Phys Fluids (1994). 2017 Feb;29(2):021901. doi: 10.1063/1.4975154. Epub 2017 Feb 9.
We study mixing in Stokesian vesicle suspensions in two dimensions on a cylindrical Couette apparatus using numerical simulations. The vesicle flow simulation is done using a boundary integral method, and the advection-diffusion equation for the mixing of the solute is solved using a pseudo-spectral scheme. We study the effect of the area fraction, the viscosity contrast between the inside (the vesicles) and the outside (the bulk) fluid, the initial condition of the solute, and the mixing metric. We compare mixing in the suspension with mixing in the Couette apparatus without vesicles. On the one hand, the presence of vesicles in most cases slightly suppresses mixing. This is because the solute can be only diffused across the vesicle interface and not advected. On the other hand, there exist spatial distributions of the solute for which the unperturbed Couette flow completely fails to mix whereas the presence of vesicles enables mixing. We derive a simple condition that relates the velocity and solute and can be used to characterize the cases in which the presence of vesicles promotes mixing.
我们使用数值模拟研究了二维圆柱库埃特装置中斯托克斯囊泡悬浮液的混合情况。囊泡流动模拟采用边界积分法进行，溶质混合的平流扩散方程则使用伪谱格式求解。我们研究了面积分数、内部（囊泡）与外部（主体）流体之间的粘度对比、溶质的初始条件以及混合度量的影响。我们将悬浮液中的混合情况与无囊泡的库埃特装置中的混合情况进行了比较。一方面，在大多数情况下囊泡的存在会略微抑制混合。这是因为溶质只能通过囊泡界面扩散而不能被平流输送。另一方面，存在这样一些溶质的空间分布情况，即未受干扰的库埃特流完全无法实现混合，而囊泡的存在却能实现混合。我们推导出了一个将速度和溶质联系起来的简单条件，该条件可用于表征囊泡的存在促进混合的情况。
