Performance Enhancement of a Vertical Tail Using Synthetic Jet Actuators

Active flow control with synthetic jets has been shown to increase aerodynamic efficiency by delaying flow separation. The application of flow control to a vertical tail of an aircraft could enable a significant size reduction of that tail. Wind tunnel experiments were conducted at Rensselaer Polytechnic Institute on a swept back, tapered tail with a 29.6% chord rudder. Flow control was implemented using eight synthetic jet actuators located just upstream of the hinge line. The mechanism of enhancement was characterized with surface pressure measurements and stereoscopic particle image velocimetry. Using flow control, the side force was increased by up to 18% at moderate rudder deflections with actuators operating at dimensionless frequency of O(10). Actuating the synthetic jets with a pulse-modulated waveform yielded superior performance at high rudder deflections. The effect of spanwise spacing was also investigated, as was the relative effect of actuators at different spanwise locations. It was demonstrated that midspan actuators provide the greatest contribution at moderate rudder deflections, and root (inboard) actuators provide the greatest contribution at high rudder deflections; this is due to the fact that the separation propagates from the tip to the root as rudder deflection increases. Moreover, due to the vertical tail sweep, the effect of each actuator is predominantly on a region outboard of its own position.