Transport of impurities in 2D incompressible periodic flows

The investigation of the motion of finite size particles with density different from that of the fluid is relevant to the study of transport in geophysical 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 impurity. The classic results (stability of the vortex centre for impurities lighter than the fluid; unstable motion for denser impurities) are reviewed. In the former case a typical convergence time scale towards the vortex centre is defined and studied as a function of the Stokes number St and the density ratio gamma. In the range of parameters under consideration it is observed that the Basset force acts as a (further) drag term modifying the convergence time without altering the qualitative features of the particle trajectory. (C) 2001 Elsevier Science Ltd. All rights reserved.