Coupling immersed boundary and lattice Boltzmann method for modeling multi-body interactions subjected to pulsatile flow

This paper numerically investigates the effect of pulsating flow on the settling dynamics of rigid circular particles. This is an interdisciplinary subject and spans several areas ranging from mathematical and numerical modeling to fluid mechanics. For this purpose, pulsatile flow characteristics are embedded in the combination of the direct-forcing immersed boundary method and the split-forcing lattice Boltzmann method. Inter-collision forces between the solid boundaries (particles and boundaries) and the added mass force due to acceleration are considered. Adequate verification tests are done to ensure the credibility of the findings. The critical parameters of pulsating flow, such as amplitude and frequency of pulsation, are investigated in detail. The paper especially puts emphasis on the interaction between particles and studies the well-known drafting, kissing, and tumbling (DKT) phenomena. Two different scenarios are taken into account and also compared with the stationary flow. The first case is when the pulsating flow is in the direction of gravity (co-flow), while in the latter, there is an opposing flow (counterflow). The sedimentation manners of 12 particles in a vertical channel are also presented. The findings shed light on the importance of pulsating flow and the extension of the proposed computational method for such problems. It is also revealed that pulsation and its variables can alter DKT by either postponing or speeding up the process. Also, in some cases, the cycle of DKT can be maintained incompletely, and particles would just stick together. The results can be useful for various engineering problems like filtration and particle sorting.