Active Control of Separated Flow

AEROSPACE & MECHANICAL ENGINEERING DEPARTMENT"Active Control of Separated Flow"Lou CattafestaAssociate ProfessorDepartment of Mechanical and Aerospace EngineeringUniversity of FloridaAbstract:Flow separation incurs a large amount of energy loss and limits the performance of many flow-related devices (e.g., airfoils, diffusers, etc.). Researchers have been trying to mitigate or eliminate flow separation for over a century because of its large potential payoff in practical applications. Numerous active separation control strategies have been attempted on civil and military aircraft and underwater vehicles with varying degrees of success. However, most of the active control approaches are open-loop in nature because of their simplicity but are often time-consuming and expensive. This talk discusses two novel adaptive feedback control approaches designed to reattach a massively separated flow over a NACA airfoil with minimal control effort using piezoelectric synthetic jet actuators and various sensors for feedback. One approach uses an adaptive feedback disturbance rejection algorithm in conjunction with a system identification algorithm to develop a reduced-order dynamical systems model between the actuator voltage and unsteady surface pressure signals. The objective of this feedback control scheme is to suppress the pressure fluctuations on the upper surface of the airfoil model, which results in reduced flow separation, increased lift, and reduced drag. A second approach leverages various flow instabilities in a nonlinear fashion to maximize the lift-to-drag ratio using a constrained optimization scheme – in this case using a static lift/drag balance for feedback. Detailed experiments are described to elucidate the baseline uncontrolled and controlled flow physics, and various technical challenges are addressed and discussed in detail.Biographical Information:Lou Cattafesta is currently an Associate Professor in the Department of Mechanical and Aerospace Engineering at the University of Florida. His primary research interests are active flow control and aeroacoustics. Prior to joining UF in 1999, he was a Senior Research Scientist at High Technology Corporation in Hampton, VA, where he was the group leader of the Experimental and Instrumentation Group. His research at NASA Langley focused on supersonic laminar flow control and pressure- and temperature-sensitive paint measurement techniques. At that time, he became involved in active control of flow-induced cavity oscillations, which provoked his current research interests in active flow control and aeroacoustics. More information regarding his research can be found at http://www.img.ufl.edu. Dr. Cattafesta has co-authored 4 papers that have received AIAA best conference paper awards and 6 US Patents and more than 100 journal and conferences papers. He is an Associate Fellow of AIAA and long-time member of the AIAA Fluid Dynamics Technical Committee.

Location: Seaver Science LIbrary Room 150

Audiences: Everyone Is Invited

Contact: April Mundy