April 21, 2025, Mark Gragston, University of Tennessee Space Institute

4:00 p.m.
190 Goodwin Hall

"Experimental Measurements of Unsteady Aerodynamic Phenomena in Hypersonic Flows" 

Abstract: Unsteady aerodynamic phenomena such as laminar-turbulent boundary layer transition, shockwave-boundary layer interactions (SBLI), and others remain difficult to model and characterize but play an import role in hypersonic flight system considerations. Experiments remain the best way to study these phenomena due to computational limitations and the wide range of conditions and parameters of interest. Work will be presented examining the influence of incoming boundary layer state on the evolution of shockwave-boundary layer interactions in hypersonic conditions, with particular focus on the surface heating near reattachment. Additionally, preliminary results and observations regarding the response of a hypersonic boundary layer to directed energy-like flow-field disturbances induced via laser-surface interactions will be discussed.

Bio: Dr. Mark Gragston has been an Assistant Professor at the University of Tennessee-Knoxville (UTK) and Space Institute (UTSI) since 2020. He received his Ph.D. from University of Tennessee-Knoxville in 2018, with work focusing on the development of laser-based diagnostics for reacting flows and plasmas. Afterwards, he was a Research Assistant Professor at UTK/UTSI working in Hypersonic aerodynamics between to 2018-2020. His current work focuses on developing measurement capabilities for studying high-speed flow phenomena such as aerodynamic heating, boundary layer transition, shockwave-boundary layer interactions, thermochemistry, and more. He was an awardee for the AFOSR Summer Faculty Fellowship Program in 2020 and 2021, conducted at Wright-Patterson AFB and Arnold AFB, respectively and also won the 2022 Louis and Ann Hoffman Research Award at UTK. Dr. Gragston holds two U.S. patents related to optical imaging and laser-based measurements and has authored over 40 peer-reviewed journal publications in the field and is also an active member of the AIAA Aerodynamic Measurement Technology (AMT) Technical Committee. He teaches courses in hypersonic flows, viscous flows, aerothermochemistry, laser diagnostics, and engineering mathematics at UTSI and UTK.