Microparticle detachment from surfaces exposed to turbulent air flow: microparticle motion after detachment

The motion of heavy microspheres after their detachment from flat surfaces is considered. The microspheres initially are in static contact equilibrium, embedded fully in the viscous sublayer and subjected to a slowly accelerating fully developed turbulent flow. The equations of motion of the microspheres are presented, including surface roughness effects. The equations are solved numerically for detachment with and without consideration of a burst–sweep event initiating detachment. The microsphere velocity along the surface after detachment is measured using a strobed laser-light sheet and compared to the numerical solutions. Results indicate that the microspheres undergo pure rolling along the surface before possible entrainment and that the sweep plays a role in the detachment process. A model for predicting the microsphere velocity along the surface after detachment is presented.