Dynamic Adhesion of Particles Impacting a Cylinder

Abstract

Adhesion efficiencies for ammonium fluorescein particles impacting a stainless steel cylinder were measured by a fluorometric technique. Below the critical velocity, the adhesion efficiency reached only 80%. When the efficiencies were divided by 0.8, they agreed with the theory of Wang¹. Counting of particles around the cylinder by a microscope showed rebound to increase rapidly with angles beyond 15° from the stagnation point, accounting for the missing 20% in the overall adhesion efficiency. The data imply that the tangential velocity component can cause particle bounce even when the normal component is below the critical velocity. The critical velocity is found to depend on particle diameter to the power -1.29, in agreement with the data of Cheng and Yeh² but in disagreement with the theory of Dahneke³. Comparison of the magnitudes of the critical velocity from various experiments suggests that the observed critical velocity is lower when the angles of impaction and rebound are not restricted to 90°.