A preliminary numerical study of the effect of mixed convection on hydrodynamic removal of contaminants contained in a cavity is carried out. The process of fluid renewal in a cavity is modeled via a numerical solution of the Navier-Stokes equations coupled with the energy equation for transient flows. Attention in the present work is focused on the effects of mixed convection on the transient development of a cavity flow and the efficiency of cleaning cavities. The results show that the change in Grashof number causes a dramatic difference in the observed flow pattern and cleaning efficiency. (C) 2003 Elsevier Science Ltd. All rights reserved.