Large-eddy simulation of flow about a rotating cylinder at large Reynolds number

Wall-resolved large-eddy simulations (LES) of flow past a rotating cylinder are described. The principal flow parameters are the dimensionless rotation speed α = Ω D/(2U∞) and the Reynolds number ReD = U∞ D/ν . We vary ReD at fixed α = 0.6 with emphasis on the lift-crisis phenomenon where, with increasing ReD, the lift coefficient CL decreases suddenly as ReD passes though a narrow, critical band. Calculations of CL and CD are compared with experimental measurements to demonstrate that the lift crisis is captured by the LES. Results show that the mechanisms that drive the lift crisis when varying ReD at fixed α are similar to those observed when varying α at fixed ReD. Both data sets support a hypothesis which interprets the lift crisis as the result of near-wall, small-scale reversal flows aggregating into a relatively narrow zone, producing small-scale incoherent separation accompanied by a deep pressure minimum. Scaling of the skin friction coefficient with Re1/2D, which was found previously for flow past a non-rotating, is also observed for α = 0.6.