Dispersed particles traveling at a high throughput in microchannels laterally migrate and focus into a streamline at each channel face. The focusing attractors within the cross-section are determined by the balance between the lift forces. However, particles in close proximity (e.g. due to high concentration and abrupt particle contact) suffer a breakdown of distinct focusing due to excessive hydrodynamic interaction. Here, I present numerical investigations into the effects of the strong hydrodynamic interaction on the inertial focusing. The direct numerical simulation is used to calculate the focusing/defocusing of particles, specifically since the particle-induced disturbance flows vary at the particle scale and hence affect the individual particle motion. The simulated defocusing of many-body systems prefer finite inter-particle separation, in contrast with sedimentation of two mobile particles, whereby the trailing particle catches up with the leading particle due to reduced drag in its wake. I numerically demonstrate that the finite separation between nearest neighbors is a consequence of hydrodynamic repulsive motion unique to wall-bound shear flows. The author further presents direct demonstrations of the effects of the strong hydrodynamic interaction on the inertial focusing in an experimentally unachievable manner. The excessive hydrodynamic interaction drastically dissipates the near-wall focusing attractors and thus causes irreversible defocusing by breaking the balance between the lift forces. Unexpectedly, I also find that moderate hydrodynamic interaction can alter focusing speed on specific conditions, suggesting that an optimum concentration may significantly boost the inertial focusing in microfluidic-based applications.

在微通道中以高通量传播的分散颗粒横向迁移并集中在每个通道表面的流线中。横截面内的聚焦吸引器由提升力之间的平衡确定。但是，粒子非常接近（例如由于高浓度和突然的粒子接触而导致的）由于过度的水动力相互作用而遭受明显聚焦的破坏。在这里，我对强水动力相互作用对惯性聚焦的影响进行了数值研究。直接数值模拟用于计算粒子的聚焦/散焦，特别是因为粒子引起的扰动流在粒子尺度上会发生变化，从而影响单个粒子的运动。与两个可移动粒子的沉降相反，多体系统的模拟散焦更倾向于有限的粒子间分离，这是由于两个尾随粒子的尾流阻力减小，使得尾随粒子追上了前导粒子。我用数值方法证明了最近的邻居之间的有限距离是壁面剪切流特有的流体动力排斥运动的结果。作者还以实验上无法实现的方式，直接展示了强流体动力相互作用对惯性聚焦的影响。过度的水动力相互作用会极大地消散近壁聚焦吸引器，从而通过破坏升力之间的平衡而导致不可逆的散焦。出乎意料的是，我还发现适度的流体动力学相互作用会改变在特定条件下的聚焦速度，这表明在基于微流体的应用中，最佳浓度可能会显着提高惯性聚焦。作者还以实验上无法实现的方式，直接展示了强流体动力相互作用对惯性聚焦的影响。过度的水动力相互作用会极大地消散近壁聚焦吸引器，从而通过破坏升力之间的平衡而导致不可逆的散焦。出乎意料的是，我还发现适度的流体动力学相互作用会改变在特定条件下的聚焦速度，这表明在基于微流体的应用中，最佳浓度可能会显着提高惯性聚焦。作者还以实验上无法实现的方式，直接展示了强流体动力相互作用对惯性聚焦的影响。过度的水动力相互作用会极大地消散近壁聚焦吸引器，从而通过破坏升力之间的平衡而导致不可逆的散焦。出乎意料的是，我还发现适度的流体动力学相互作用会改变在特定条件下的聚焦速度，这表明在基于微流体的应用中，最佳浓度可能会显着提高惯性聚焦。过度的水动力相互作用会极大地消散近壁聚焦吸引器，从而通过破坏升力之间的平衡而导致不可逆的散焦。出乎意料的是，我还发现适度的流体动力学相互作用会改变在特定条件下的聚焦速度，这表明在基于微流体的应用中，最佳浓度可能会显着提高惯性聚焦。过度的水动力相互作用会极大地消散近壁聚焦吸引器，从而通过破坏升力之间的平衡而导致不可逆的散焦。出乎意料的是，我还发现适度的流体动力学相互作用会改变在特定条件下的聚焦速度，这表明在基于微流体的应用中，最佳浓度可能会显着提高惯性聚焦。