Peristaltic transport of elliptic particles: A numerical study

Peristaltic transport of elliptic particles suspended in Newtonian fluids is numerically investigated in a planar channel formed between two flexible membranes. Numerical results were obtained under creeping-flow conditions for centered and off-center particles using the lattice Boltzmann method. The results demonstrate the importance of aspect ratio and initial inclination angle on peristaltic transport of solid particles. For a domain comprising just one wave, it was shown that, in free-pumping mode, circular particles move faster than elliptic particles and experience less shear stress. They also resist a larger adverse pressure gradient before they are finally brought to rest. Above a critical Reynolds number, however, elliptic particles are predicted to move faster than circular particles. The effect was attributed to the vulnerability of circular particles to hydrodynamic instability, which is exhibited by the particle detaching itself from the centerline, thereby adopting a longer trajectory. This is the first time that peristaltic transport of elliptic particles is being numerically studied, and the results can be used for designing peristalsis-based micro-swimmers or microfluidic systems deemed for single-cell studies.