On resuspension of spherical particles from rough and smooth surfaces by a wall-normal vortex

A three-dimensional particle tracking velocimetry (3D-PTV) method was applied to study in details the single-particle resuspension (lift-off) events of large spherical particles. In order to increase statistics, we have utilized a wall-normal, tornado-like vortex that lifted the particles from surfaces of different roughness. Analyzing the three-dimensional particle trajectories, velocities and accelerations before, during and after the resuspension events, the resuspension efficiency was obtained directly. The results show that the lift-off efficiency from the rough surface is significantly higher than from the smooth one. We suggest a simplified mechanistic model based on the mobility parameter that can predict this peculiar effect. This study can lead to improved modeling of resuspension rates from smooth and rough beds.