Closed Loop Flow Control of a Tangent Ogive at a High Angle of Attack

Abstract

The flowfield around an axisymmetric forebody at a moderate angle of attack (40 � < � < 60 � ) produces a significant side force as the result of an asymmetric pressure distribution around the body resulting from an asymmetric vortex flow state. Numerical studies of open-loop control using mass-blowing slots near the tip of the model have shown proportional control of the side force by varying the momentum coefficient of the blowing slots. From the open-loop simulations, a prediction-error minimization method (PEM) was used to develop a linear time invariant (LTI) model which captures the dynamics of the side force response to different mass flow rates applied to the port or starboard actuator. Based on the model, a PI controller was developed for reference tracking a prescribed side force profile. The development of the LTI model, and corresponding controller simulations of the closed-loop system are presented to illustrate the models capabilities as well as its limitations. The ability to track a prescribed reference signal based on the LTI model and corresponding PI control scheme is shown. The results indicate that the bandwidth of the controller is limited to frequencies below half the convective frequency due to the convective time delay as well as the actuator and sensor placement. Finally, the closed-loop controller simulations are compared to Navier-Stokes feedback simulations.