Secondary flows and heat transfer in shallow flow around a cylinder: LES, PIV

Abstract

We report on Large-eddy simulations (LES) of flow around a short cylinder mounted in a narrow plane channel in a range of Reynolds numbers 1000, 2000, 3750 based on the bulk velocity of the flow and diameter of the cylinder supplemented with Particle image velocimetry (PIV) measurements for the highest considered Re. First two cases appear to be steady, however, for Re=3750 the flow becomes unsteady with the wake dominated by periodic vortex shedding. In front of the cylinder typical horseshoe vortices are identified intensifying the skin friction and heat transfer on the wall, while in the near wake we observe a quasiperiodic low-frequency secondary motion in the form of a pair of counterrotating eddies developing in the transverse direction. The Karman vortex street remains the dominant pattern, but further downstream from the cylinder the transport across the channel is associated with the secondary streamwise vortices, as also previously observed in slot jets. We observe their impact on heat transfer and skin friction on the wall of the channel.