Numerical simulation of liquid mixing inside soft droplets with periodic deformation by a lattice Boltzmann method

Abstract

Abstract In this work we applied lattice Boltzmann (LB) method to investigate the mixing performance and hydrodynamics inside droplet passing through baffled channels periodically. Specifically, a color-gradient model was employed to simulate micro-droplet motions and a LB algorithm of passive tracer was added to characterize mixing inside droplet without any influence on the macroscopic fluid motions. Our simulation results show that the added baffle in microchannels would force the droplet to deform, which leads to dynamically changing internal recirculation and thus enhancing mixing performance. The internal circulation periodically changes according to the length of the baffle; the local field is much similar to that in straight channels with the same channel width. By comparing the intensity of mixing in the cases with different initial species distributions, we found that coordination between circulation area and heterogamous region of tracer plays an important role in mixing performance because stream trajectories directly distribute the species into lower concentration region. In addition, our results show that the location of baffle is another influencing factor contributing to enhance mixing due to the effect of droplet rotation. Results in this work would be greatly helpful for analyzing the practical process design and constructing the microchannel geometry.