Unsteady Aerodynamic Loads Effected by Flow Control on a Moving Axisymmetric Bluff Body

The coupling between a moving axisymmetric bluff body and its wake is modified in wind tunnel experiments using controlled interactions between an azimuthal array of fluidic actuators and the cross flow over its aft end. Enhancement or suppression of the flow coupling has profound effects on the global unsteady aerodynamic loads on the moving body and the evolution of its near wake. The model moves in six degrees of freedom along a prescribed trajectory using eight servocontrolled support wires with inline force transducers that are operated in closed-loop with feedback from a motion analysis system. Actuation is effected by an integrated azimuthal array of four aft-facing synthetic jet actuators around the perimeter of the tail end such that each actuator effects a time-dependent segment of local flow attachment over the aft surface. The present investigation focuses attention on the reciprocal relation between the response of the nearand farwake to the actuation and the associated changes in the induced aerodynamic loads when the body executes nearly time-harmonic pitch over a range of reduced oscillation frequencies (up to k = 0.26). The response of the wake to stabilizing and destabilizing actuation programs that effect reduction or enhancement of the aerodynamic loads are investigated using particle image velocimetry (PIV) and hot wire anemometry in the near and far wake, respectively. It is shown that this flow control approach induces aerodynamic loads that are comparable to the loads on the baseline configuration, and therefore may be suitable for in-flight stabilization.

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