Numerical study on the lateral migration of a deformable particle in rectangular channels

We numerically investigate the lateral migration of deformable particles in rectangular-channel Poiseuille flow using a fictitious-domain method with distributed Lagrange multipliers. Compared with rigid particles, deformable particles experience significantly deformation-induced lift, driving them toward the channel corners. During migration, soft particles remain farther from the wall than stiff particles and, after reaching a corner, shift away from the corner along the bisector, whereas stiff particles attain stable equilibrium at the corner. In the case of cylindrical particles, migration is irregular and accompanied by stronger vorticity, enhanced cross-stream velocities, and continuous tumbling with pronounced deformation. By focusing on rectangular-channel geometry, this work reveals deformability-dependent corner migration and finite-offset equilibria that are absent in rigid-particle dynamics, and extends the analysis to deformable cylinders to expose shape-driven irregular migration and tumbling.