Resolved Fluid-Particle Simulation of Pattern Formation in Flow of Suspensions in Square Channels
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The study of suspensions in narrow channels is interesting both from a fundamental science perspective and with regard to applications in microfluidics devices. Since the discovery by Segré and Silberberg that particles in pipe flow migrate to an off-center equilibrium position, half a century has passed and much research on the topic has been performed. It has been reported in literature that in square channels, eight equilibrium positions exist: four close to the corners and four close to the face centers. The position and stability of these positions depends on channel Reynolds number and ratio of particle diameter and channel width, and is well-known in the single-particle limit. However, little is known about the physics of more dense suspensions.
We present fully resolved simulations of a suspension of spheres in a quasi-infinite square channel using LBDEMcoupling. The solid fraction in the domain is varied in the range of 0.01%-3% at several Reynolds numbers. At 0.01% solid fraction, we are able to reproduce experimental results. Several yet unknown patterns arise when the solid fraction in the channel increases, such as instability of the face equilibrium positions and multiple band formation parallel to the channel walls. The origin of these patterns lies in the hydrodynamic interaction between the particles. With this study, we broaden the range of known effects of suspensions in channel flow and hope to lay a foundation for future applications.