Behavior of three circular particles in a confined power-law fluid under shear

We studied the interactions among three circular particles suspended in a power-law fluid undergoing confined shear flow in two dimensions. The calculations are based on our previously developed lattice Boltzmann direct-forcing/fictitious-domain method. Reynolds numbers 1 ⩽ Re ⩽ 20 and power-law indices 0.5⩽n⩽1.5 were considered. We roughly classified the particles' motion into “returning” and “passing” behaviors. We found that the particles are more likely to pass for higher Reynolds numbers or lower power-law indices, given the same flow conditions. In particular, we investigated the dynamics of the particles in shear flows and find two peaks in the horizontal fluid (drag) force for large Reynolds number or small power-law index. The first peak serves to decelerate the particles, while the second does the opposite, and might be primarily responsible for the transition from the “returning” to the “passing” behavior. We also studied the effects of the Reynolds number and the power-law index on particle velocity and streamline patterns.