Synthetic jet actuation strategies for momentumless trailing edge wake

Abstract

Periodic addition of momentum employing a Trailing Edge Synthetic Jet Actuation (TESJA) to control the wake of a blunt trailing edge plate was investigated experimentally at Reynolds number Reh=U∞h/ν=7200, based on the trailing edge thickness, h. A pair of synthetic jets were symmetrically placed at the model base. Two-component PIV measurements were reported for natural wake and actuated wakes under different actuation strategies namely asymmetric actuation, symmetric synchronous dual-actuation, and out-of-phase dual-actuation. A pair of synthetic jets were symmetrically placed at the model base. Two positions of the TESJA on the model base (peripheral or central position) were also studied and discussed. The forcing was applied at a frequency of 0.75 the natural vortex shedding frequency, while a high momentum addition coefficient of up to 24% was applied to balance the momentum deficit and to accomplish a near momentumless state. The measurements revealed that the application of TESJA reduced the extent of the separation bubble and redistributed energy among the Reynolds stresses. A perfect lock-in of vortex shedding in the wake was achieved. The actuation efficiency depended on both the applied control strategy and the actuators' positions. Forcing was found to be most effective in achieving a near momentumless state when applied at base model extremities (peripheral configuration) to permit the interaction of synthetic jet with the neighbouring shear layers and a large entrainment. The above strategies and positions led generally to three actuated wake states: (1) vortex pair shedding vectoring for asymmetric forcing, (2) symmetric vortex shedding under in-phase synchronous forcing, and (3) alternate vortex shedding with increased vorticity and turbulence, combined with a large momentum addition when out-of-phase forcing was applied.