Flow Control over a Conical Forebody by Duty-Cycle Actuations

Duty-cycle modulation alternately blowing from two opposite-facing plasma actuators on the leeward surface near the apex of a cone with a 10° semi-apex angle is adopted to control mean lateral force and moment, and the flow control mechanisms are presented. Pressure distributions over the forebody of the cone are measured by steady and unsteady pressure tappings. The experiments are performed in a 3.0 × 1.6 m open-circuit wind tunnel at a wind speed of 20 m/s, a 45º angle of attack and a Reynolds number of 2 × 105, based on the diameter of the base of the cone. Almost linear proportional control of the lateral forces and moments over a slender conical forebody at a high angle of attack has been demonstrated by employing a pair of single dielectric barrier discharge plasma actuators near the apex of the cone, combined with a duty-cycle technique. The pressure distribution measurements indicate that the bi-stable vortex pattern appears to be shifted in the opposite direction when the port or starboard actuator is activated, while the other is kept off during the test. It is shown that the reduced pulse-repetition frequency based on the local diameter at the plasma actuator equal to one yields the highest effectiveness among the cases considered.