Numerical characterisation of active drag and lift control for a circular cylinder in cross-flow

Abstract

Synthetic jet actuators have shown promise to control drag and lift for a bluff body in cross-flow. Using unsteady RANS CFD modelling, a significant modification of the drag coefficient for a circular cylinder in cross-flow at Re = 3900 is achieved by varying the actuation frequency. The variation in actuation frequency corresponds to a range in Stokes number of 2.4 < Sto < 6.4. The trends in drag coefficient modification largely agree with the findings of past publications, achieving a maximum drag reduction at Sto = 4.9 for a fixed jet Reynolds number of the synthetic jet of ReŪo = 12. A decrease in the adverse pressure gradient near the jet orifice correlated with a momentum increase in the viscous sublayer and stronger vortical structures at the rear of the cylinder. In these same conditions, a decrease in turbulence intensity was observed in the far field wake, which is a relevant finding in the context of wind and tidal turbine arrays.