Doostmohammadi A, Ardekani A M
Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2013 Aug;88(2):023029. doi: 10.1103/PhysRevE.88.023029. Epub 2013 Aug 30.
The anisotropic structure of fluidized suspensions is governed by their microstructures which are in turn determined by the dynamics of particle pair interactions. Here, we present a numerical simulation of particle interaction in linearly stratified fluids. It is shown that unlike homogeneous fluids, stratification results in the attraction of particles settling abreast. The attraction between the particles is characterized by the combined effects of buoyancy, inertia, and diffusion. The interaction of the particles settling in tandem can be fundamentally altered due to the presence of the background density gradients and the drafting-kissing-tumbling behavior in a homogeneous fluid can be replaced by drafting-kissing-separation or drafting-separation phenomenon depending on the strength of the stratification. In the case of weak stratification, drafting-kissing-tumbling occurs, however, a prolonged kissing time is observed and the rate of change of the orientation of particles is reduced. It is shown that the formation of the buoyancy-induced vortical structures and the generation of stratified jets behind the particles are the fundamental mechanisms in governing the dynamics of the particle pair interaction in stratified fluids.
流化悬浮液的各向异性结构由其微观结构决定，而微观结构又由颗粒对相互作用的动力学所决定。在此，我们给出了线性分层流体中颗粒相互作用的数值模拟。结果表明，与均匀流体不同，分层会导致并排沉降颗粒之间产生吸引力。颗粒之间的吸引力由浮力、惯性和扩散的综合作用所表征。由于背景密度梯度的存在，串联沉降颗粒之间的相互作用可能会发生根本性改变，并且均匀流体中的“拖曳-碰撞-翻滚”行为可能会被“拖曳-碰撞-分离”或“拖曳-分离”现象所取代，这取决于分层的强度。在弱分层的情况下，会发生“拖曳-碰撞-翻滚”，然而，会观察到较长的碰撞时间，并且颗粒取向的变化速率会降低。结果表明，浮力诱导的涡旋结构的形成以及颗粒后方分层射流的产生是控制分层流体中颗粒对相互作用动力学的基本机制。
