Particle sedimentation in active nematic fluid within a square tube

Active fluids can influence the behavior of passive particles, with sedimentation being an important such process. We investigate how the velocity of a sphere varies when settling in a square tube filled with active nematic fluids. While the direct active forces exerted on the sphere are weak in our study, activity can still significantly modify settling velocity by altering the flow structure and nematic field. The results manifest mechanisms of activity-induced shear thinning and thickening for various anchoring conditions and activity. As activity increases, transitions between flow patterns further influence settling, with different effects observed in extensile and contractile fluids.