Transport of impurities in 2D incompressible periodic flows

The investigation of the motion of finite size particles with density diffe rent from that of the fluid is relevant to the study of transport in geophy sical flows. A two-dimensional model of an incompressible periodic flow is used in order to assess the role of the different forces acting on the impu rity. The classic results (stability of the vortex centre for impurities li ghter than the fluid; unstable motion for denser impurities) are reviewed. In the former case a typical convergence time scale towards the vortex cent re is defined and studied as a function of the Stokes number St and the den sity ratio gamma. In the range of parameters under consideration it is obse rved that the Basset force acts as a (further) drag term modifying the conv ergence time without altering the qualitative features of the particle traj ectory. (C) 2001 Elsevier Science Ltd. All rights reserved.