Resuspension by Droplets

Abstract

Most of the work on hydrodynamic resuspension has concentrated on the lift (and drag) forces generated by motion in the turbulent boundary layer beneath some mean flow. In the fluvial context, this hydrodynamic mechanism represents the dominant component of resuspension for most naturally occurring particle-laden flows. However, in the aeolian context, the hydrodynamic mechanism has great difficultly resus-pending fine dust particles, although may often resuspend larger ‘sand’ particles. It is then the saltating of these sand particles (which perform a series of approximately parabolic hops along the ground) that drives the ballistic mechanism of direct mechanical interaction that is capable of resuspending the finer dust. Further details may be found in the many review articles on both these processes (e.g. Willets 1998). An additional hydrodynamic mechanism, whereby the wake of a colliding particle can play a role, has explored recently by Eames & Dalziel (2000). The resuspension mechanism driven by droplets, however, turns out to be quite different.