Patterns of vortex generation behind a cylinder in a wall-bounded cross-flow during transition to turbulence

Abstract

The paper elaborates on experimental investigation and direct numerical simulation of the wake flow behind a circular cylinder located near the wall of a rectangular channel. The study considers the Reynolds number range that covers transition to turbulence in the wake. Spiral fluid motion directed from the sidewalls to the channel center is revealed behind the cylinder for both positions of the cylinder considered in the study. The paper describes the effect of this motion on the critical Reynolds number corresponding to the onset of Karman vortex street and on the vortex topology. The spiral motion is shown to correlate with the onset of low-pressure regions behind the cylinder near the sidewalls. These regions result from the interaction between the boundary layer on the sidewalls and the separation region behind the cylinder.