Large-Eddy Simulation of Flow Over a Circular Cylinder With Plasma-Based Control

Abstract

Control of flow over a circular cylinder by means of plasma actuators is numerically investigated. Large-eddy simulations are carried out for Reynolds number of 30, 000 based on free-stream velocity and cylinder diameter. The effect of plasma is represented by a body force field in the Navier-Stokes equations using a plasma actuation model. Both steady actuation and unsteady actuation are studied and, in the unsteady case, the effect of actuation frequency is examined. The configurations considered include four actuators and two actuators. Results from baseline simulations without control show reasonable agreement with previous experimental results in terms of wake turbulence statistics and shear-layer characteristics. Similar to experimental observations, small-scale fluid motions due to shear-layer instability are found immediately behind the cylinder. With four actuators turned on at θ = ±90 and ±135 from the front stagnation point, the separation point is delayed drastically due to the electric body forces generated by the plasma. As a result, large-scale vortex shedding is virtually eliminated by both steady and unsteady actuation, and the mean drag as well as drag and lift fluctuations are significantly reduced. The frequency of unsteady actuation has a large effect on the control performance when it is varied from Stc = 0.5 to 1, whereas between Stc = 1 and 1.5 the control performance is relatively unchanged. With only two actuators at θ = ±90, the control is much less effective with steady actuation but is nearly as effective as in the four-actuator case with unsteady actuation at Stc = 1.