Virtual control surfaces for the optimization of steady and unsteady airloads on a compressor cascade are assessed numerically. The effects of mechanical surfaces are realized with plasma actuators, located both on the pressure and on the suction side of the blade trailing edge. Suction side plasma actuation is thought to reproduce the effects of mechanical wing spoilers, whereas pressure side plasma actuation is meant to act as a mechanical Gurney flap. Indeed actuators are operated to generate an induced velocity field that is opposite relative to the direction of the freestream velocity. As a consequence controlled recirculating flow areas are generated, which modify the effective mean line shape, as well as the position of the Kutta condition application point - and in turn the developed airloads. Proper triggering of pressure/suction side actuation is found to be effective in altering the blade loading, with effects comparable to mechanical control surfaces. Traveling wave mode simulations show that significant reductions in the peaks of the blade pitching moment can be achieved for multiple inter blade phase angles. It is proved that virtual control surfaces can provide effective load alleviation on the cascade, without failures likely to occur on mechanical devices under temperatures and centrifugal fields typical of aero engine compressors.
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