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Aerodynamic Flow Control of Axisymmetric Bodies

The aerodynamic forces on an axisymmetric body are altered by fluidic interaction of an azimuthal array of integrated synthetic jet actuators with the cross flow.  Actuators are integrated into a Coanda surface on the aft section of the body, and the jets emanate from narrow, azimuthally segmented slots equally distributed around the perimeter.  The model is suspended in the tunnel with two configurations.   The first uses eight mounting wires, each comprising miniature in-line force sensors and shape-memory-alloy (SMA) strands that are used to measure the instantaneous forces and moments and control the model orientation, respectively.  The interaction of the actuation jets with the flow over the moving model generates transitory aerodynamic loading effected by coupling between the induced motion of the aerodynamic surface and the fluid dynamics that is driven by the actuation.  It is shown that these interactions can lead to effective control of the aerodynamic forces and moments throughout a range of different orientations.  The second configuration uses a single mounting wire which allows the model to be free to yaw, but constrains the model in all other directions.  In this configuration, the model has a baseline oscillatory response to the flow. 

Continuous actuation control with either one or both control jets in the plane of motion demonstrates that open loop control can be applied to either suppress natural oscillations of the model by up to about 60%, or to shift the center of the body oscillations of up to about 30% of the baseline oscillation.  A PID closed-loop control is developed and utilized to control a desired trajectory of the model.  The model’s measured displacement is used as the control input, while the amplitude modulation of both of the jets prescribed outputs at the fixed actuation frequency is the control output.  The present experiments demonstrate that this fluidic actuation paired with a closed-loop control is capable of dramatically suppressing the model's unstable yaw oscillations, often in excess of 90%.  Furthermore, the same controller can dramatically amplify natural oscillation, up to several-fold of the natural amplitude.

Supported by ARO