CIMMS Lunchtime Series: Lessons Learned from Recent Experiments on Active Flow Control

Dr. Hassan M. Nagib, John T. Rettaliata Distinguished Professor of Mechanical & Aerospace Engineering, Illinois Institute of Technology, Chicago, IL

Recently, there have been a number of successful demonstrations of the effectiveness of Active Flow Control (AFC) for manipulating flows exhibiting large separated regions in fixed-wing and rotorcraft applications. These demonstrations, included flight tests and large wind-tunnel experiments, and primarily utilized open-loop periodic AFC methods. Based on observations made during these studies, a series of wind tunnel tests and computations were recently carried out using a hump model to generate a flow with a large separation region starting from a meandering location, to compare different types of steady, oscillatory, and pulsed AFC containing blowing and/or suction components. The results of these tests provided valuable insight into physical mechanisms by which various AFC methods affect the flow, and suggest that suction (or the suction component of oscillatory AFC) has the greatest effect on the flow. Hysteresis in the response of the flow to AFC suggests that non-periodic pulsed techniques can improve efficiency of the AFC system and make it more suitable for closed-loop control. The discussion will also include what lessons we have learned that might have an impact on models suitable for reduced-order closed-loop control, with an eye on application to transient behavior as the flow changes between steady-state configurations.