Impact of shape on particle detachment in linear shear flows

Abstract Transport and detachment of colloidal particles with irregular shapes occur in geology, environmental, and water-resource engineering. We investigated the effect of shape and aspect ratio on the detachment of non-spherical microparticles attached to a plane substrate, in Couette linear shear flow, under favourable conditions. The detachment conditions were determined by the mechanical equilibrium of drag, lift, gravity and adhesion forces acting on the particle. Drag and lift were evaluated using Computational Fluid Dynamics (CFD), introducing the shape-dependent corrections into traditional formulae for spherical particles. The adhesive particle–surface force is determined by the Surface Element Integration (SEI) method, which also corrects the classical DLVO expression. The forces exerted on spheroids and cylinders can significantly differ from spheres and their detachment exhibit non-monotonic dependencies with aspect ratio. Direct visualisation experiments were performed by piecewise-constant change of flow velocity and the observed detachment were in good agreement with the mechanical-equilibrium based predictions.