3D vortex structure investigation using Large Eddy Simulation of flow around a rotary oscillating circular cylinder

Three-dimensional turbulent flow over a circular cylinder performing sinusoidal rotational motions around its axis is investigated using Large Eddy Simulation (LES). The simulation is carried out for Reynolds number equal to 3900 with rotation rate (Ω=θosc*r∕U0, where θosc is oscillation amplitude, r cylinder radius, and U0 flow velocity) varying from 0.5 to 2; and with non-dimensional forcing frequencies (ratio of the frequency of the cylinder oscillation and that of the vortex-shedding from a stationary cylinder) from 0 to 8. Time-averaged flow parameters as well as mean drag and lift coefficients, mean base pressure coefficient, and separation angle and mean length of the vortex formation region are obtained and thoroughly analyzed. It was found that under forcing control, 50% of drag reduction was achieved and the flow three-dimensionality was reduced in the lock-on range.