Two Dimensional Simulations of a Feedback Controlled D-Cylinder Wake

Two dimensional feedback control simulations of the wake behind a D-shaped Cylinder are compared to feedback controlled circular cylinder results. A low dimensional model based on Proper Orthogonal Decomposition (POD) in conjunction with real time Linear Stochastic Estimation (LSE) is used to estimate the flow state. At laminar Reynolds numbers of up to 300, the von Karman Vortex Street can be strengthened or weakened depending on the phase shift applied in the controller. As opposed to the circular cylinder simulations, where actuation was implemented by translating the cylinder normal to the flow, the D shaped cylinder wake is controlled using two blowing and suction slots near the base of the model. Since the D shaped cylinder features a fixed separation point, this investigation truly demonstrates that our control approach controls the wake instability and not the separation location. Results of the high resolution simulations of the feedbackcontrolled truth model show a reduction in unsteady lift force of 40%, and a reduction in drag of 10% of the unforced flow field, using linear proportional fixed gain feedback of the first POD mode.