Experimental and numerical study of inertial particle clustering mechanism in a laminar stirred flow

Abstract Isolated mixing regions (IMRs) in high‐viscosity laminar stirred tanks reduce mixing efficiency but enable new solid–liquid separation and localized reactions. This work establishes an experimental and a modeling methods for inertial particle clustering. Experiments show that particle density and Reynolds number of the fluid control ring‐like clustering. Simulations reveal buoyant particles are attracted to the IMR via slow manifold attraction and “Sweep‐Stick” mechanism and locked onto closed IMR orbits (Lissajous‐like trajectories) by the pressure gradient force. The “orbital classification” phenomenon of binary particles is found. Lighter buoyant particles approach the higher‐vorticity region of the IMR, while heavier particles are pushed to the periphery. A novel clustering criterion is proposed in three‐dimensional laminar stirred flows. The study enables a deeper insight into the dynamics of inertial particle migration and clustering, and provides a new paradigm for the design of solid–liquid separation and localized reaction environments.