IGM Colloquium: Prof. Phillip J. Ansell, University of Illinois
Dynamic Stall of Pitching Wings at Transitional Reynolds Numbers
Dynamic stall is a complex phenomenon in aerodynamics, which occurs for wings and bodies subject to unsteady separation due to rapid changes in relative freestream conditions. The onset of dynamic stall is associated with drastic increases in flow field unsteadiness, producing high levels of airframe vibratory loading as well as an overall impairment of vehicle aerodynamic performance. While it is most commonly regarded as a hazard for rotorcraft in forward flight, dynamic stall can also occur for wind turbines and fixed wing aircraft under severe gust loading and during rapid maneuvers. The transient and highly unsteady nature of these types of flow fields make them substantially difficult to predict and simulate, particularly with the increases in the distribution of characteristic length scales brought about by increasing Reynolds number. In order to better understand the flow physics of dynamic stall, a series of experimental campaigns have been performed at the University of Illinois on pitching airfoil and finite wing geometries. These studies cover a range of transitional Reynolds numbers (1 × 105 – 1 × 106) and focus on fundamental aspects of the flow field leading up to emergence of dynamic stall vortex structures. Specific attention is given to characterizing oscillatory scales of interest, identification of separation bubble structures and off-body flow structures, and understanding the influence of the trailing vortex system on unsteady separation.
Dr. Ansell is an Assistant Professor in the Department of Aerospace Engineering at the University of Illinois at Urbana-Champaign. He earned his BS in Aerospace Engineering from Penn State University, and his MS and PhD in Aerospace Engineering from the University of Illinois at Urbana-Champaign. He is the director of the Aerodynamics and Unsteady Flows research group at Illinois, which specializes in subsonic and transonic experimental research on flow control, unsteady aerodynamics, and novel aerodynamic configurations. He has received Young Investigator Awards from AFOSR (2015) and ARO (2017), and was included in the Forbes 30 Under 30 list in 2016 under the Science category.