Seminar: Large-Eddy Simulations of the Onset of Airfoil Dynamic Stall at a Reynolds Number of 1.0 x 10^6

Dynamic stall due to a constant pitch-rate motion is investigated on the NACA 0012 airfoil at Re = 1.0 x 10^6 through the use of large eddy simulation. At this Reynolds number it is shown that turbulent separation moves upstream across much of the airfoil suction surface. When separation reaches the leading edge separation bubble, a bursting-event is initiated that results in a strong coherent leading edge vortex structure. This vortex wraps up the turbulent shear layer to form a large dynamic stall vortex. These results help to clarify previous experimental works that were not capable of measuring boundary layer interactions prior to vortex development. The sensitivity of these interactions to various pitch-rates and the use of a thinner NACA 0009 airfoil are briefly discussed. Finally, high-frequency forcing at the leading edge is introduced with the intent of eliminating the bubble bursting event and delaying the onset of dynamic stall. It is shown that bubble bursting is eliminated through control, but that the delay of dynamic stall is due to a slower upstream propagation of turbulent separation. A dynamic stall vortex eventually forms through the roll-up of the separated turbulent boundary layer, noticeably downstream of the uncontrolled case. The combined use of high-fidelity simulations and high-frequency flow control clarifies the roll of the laminar separation bubble in defining the onset of the dynamic stall process.

About the Speaker

Dr. Stuart Benton is a Senior Researcher for the Ohio Aerospace Institute supporting research at the U.S. Air Force Research Laboratory. He is working with Dr. Miguel Visbal to utilize the large-eddy simulation approach to study the unsteady boundary layer interactions that lead to airfoil dynamic stall. Dr. Benton received his Ph.D. from The Ohio State University in 2015. His research has focused on developing and improving flow control concepts for greater aerodynamic efficiency and performance. This body of work has used a wide array of experimental and computational techniques to provide high-fidelity measurements of the unsteady fluid dynamic interactions. 

Hosted by Professor Jeffrey Bons