Aerodynamic Control of Coupled Body-Wake Interactions

The unsteady interactions between fluidic actuators and the cross flow over the aft end of a moving bluff body are exploited for modification of the global unsteady aerodynamic loads in wind tunnel experiments using a moving axisymmetric model. The model moves in combined pitch and yaw which is designed to mimic the natural unstable motion of a similar airborne platform in the absence of roll. Actuation is effected using an azimuthallysegmented array of four aft-facing synthetic jet modules around the tail end of a model, and motion is effected by eight mounting wires that are attached to servo motors for timedependent, six degrees of freedom motion along a prescribed trajectory. Enhancement and suppression of stabilizing aerodynamic loads on the model are each investigated using coupled force and moment measurements and stereo particle image velocimetry in the near wake, at reduced frequencies of up to 0.26. The present measurements show significant suppression (up to 80%) and augmentation (up to 40%) of the platform’s motion-induced aerodynamic forces or moments with concomitant controlled deflection and decoupling of the near-wake from the motion of the body. The present investigations show that the effects of actuation on the near wake of the body are comparable to the effects of its baseline unstable pitch and yaw motion and therefore can be used to induce aerodynamic loads that cancel or enhance the baseline loads to effect dynamic steering and stabilization.

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