Large Eddy Simulation of high-Reynolds number flow past a rotating cylinder

In the present study, uniform flow past a rotating cylinder at Re = 140,000 is computed based on Large Eddy Simulation (LES). The cylinder rotates with different spin ratios varying from a = 0 to a = 2, where a is defined as the ratio of the cylinder’s circumferential speed to the free-stream speed. The Smagorinsky model is applied to resolve the residual stresses. The present commercial code is validated based on available numerical and experimental data. The results agreed fairly well with these data for the cases of the flow over a stationary and over a rotating cylinder. As the spin ratio increases, the mean drag decreases and the mean cross-stream force acting to the cylinder increases. The vortices (time-averaged) downstream of the cylinder are displaced and deformed and the vortex that is close to the region of the fluid’s acceleration shrinks and eventually collapses. By increasing a, the flow is also stabilized. It is observed that the vortex shedding process is suppressed. Specifically, the flow is unstable in load terms for spin ratios up to 1.3. After this critical value, the flow is transitional for a few dimensionless time units demonstrating the well-known von-Karman vortex street and then it becomes stable with almost constant loads. An encouraging outcome resulting from this study is that the LES computations could be accurate for high-Re sub-critical flows with grids of medium resolution combined with a validated sub-grid scale model and a low-diffusive discretization scheme.