Interaction vortex - boundary layer : numerical study of wall mechanisms

¹ LIMSI-CNRS, UPR 3251, BP 133, F-91403 Orsay Cedex, France
² Institut de Mécanique des Fluides de Toulouse, UMR 5502 CNRS/INP-UPS, Université Paul Sabatier, 118 Route de Narbonne, F-31062 Toulouse Cedex, France

Abstract

The interactions between a coherent vortex structure and a flat plate boundary layer are investigated. The unsteady numerical method used associates the Vortex-In-Cell algorithm for the convection step to the Random Walk algorithm for the diffusion one. The boundary layer is discretized by a large number of vortices, 10⁵. An appropriate choice of discretization parameters leads to a good solution for the flat plate and exhibits a minimal numerical dissipation. Interactions are studied for different Reynolds numbers, for positive and negative vortices. The Lighthill's mechanism of production of vorticity is observed. In the case of a negative vortex, a recirculation zone appears and a secondary structure with positive vorticity is created inside the boundary layer. The ejection of this structure induces the rebound of the main vortex. The wall mechanisms, particularly the study of C_f and C_p evolutions, confirm previous behaviors.