Reorganization of Coherent Structures Downstream a Circular Cylinder Located between Two Parallel Walls

Experiments were performed at low Reynolds numbers in the range ۷۵ Re ۲۷۵ in the wake of a circular cylinder of dc diameter placed symmetrically between two parallel walls of H height. ۲D۲C particle image velocimetry (PIV) was used to investigate the flow downstream the cylinder. In the unsteady flow regime downstream the cylinder, the detached primary vortices (Pi) interact with walls generating secondary ones (Pi’) and modify the cylinder wake dynamic. The kinematical properties (advection velocity, circulation, rotation kinetic energy, etc.) of the generated secondary vortices are studied and compared with the primary ones in order to show how the walls influence the von Kármán vortex street. The authors propose here a relation between the circulations and kinetic energies of primary and secondary vortices.

Keywords:

Confined cylinder wake , ۲ criterion , PIV measurements , Von Kármán vortices , Coherent structures , Wall , Vortex interaction