Experimental verification of a novel actuator signal for efficient synthetic jet

Circular cylinder separation control with synthetic jet has been investigated in a water channel. The jet issues from a slot and ejects toward downstream from the back stagnation point of the cylinder. In order to improve the effect of synthetic jet on separation control, we adopt a novel actuator signal which alters the ratio of the time duration of the suction and blowing cycles in one period. The experiments indicate that when the normal sine actuator signal is adopted, as Re_U based on average exit orifice velocity is increased, the separation region behind the cylinder decreases and the separation point delays. When Re_U is about greater than 430, the separation region disappears and the flow over cylinder is fully attached. Along with the blowing and suction cycles of the synthetic jet, the wake region behind the cylinder will appear a periodic opening and closuring phenomenon and thus suppress the Karman vortex shedding. Adopting the novel signal and fixing Re_U, when decreasing the suction duty factor k, the effect of synthetic jet on separation control is reduced; when increasing k high enough, the exit orifice velocity and vortex strength increase greatly and the effect of the synthetic jet on separation control is significantly improved, which validates the effect of the novel signal on the synthetic jet for flow control.