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Wednesday, March 23, 2022 – 12:00PM to 1:00PM
Graham V. Candler
The Boundary Layer Transition and Turbulence (BOLT) sounding rocket flight experiments are designed to make detailed measurements of boundary layer transition and turbulence at hypersonic conditions. BOLT has a complex nose geometry, highly swept leading edges and a concave surface, which challenge the validity of conventional stability analysis methods. At the University of Minnesota, we have been developing new approaches for predicting instability growth and boundary layer transition for complex geometry flows. The seminar will discuss results and progress using high-order, low-dissipation numerical methods to perform "quiet" direct numerical simulations of the BOLT flow field. The simulations reveal four competing instability mechanisms; these include second-mode acoustic disturbances, a vortical mode associated with boundary layer roll-up on the centerline, traveling crossflow due to boundary layer distortion near the leading edge, and a multi-mode instability near the trailing edge. It is shown that breakdown to turbulence occurs due to interactions between the crossflow and acoustic modes. The prospects for extending the simulation approach to include the effects of free-stream turbulence and particulates will also be discussed.
Graham Candler is the Russell J. Penrose and McKnight Presidential Endowed Chair of Aerospace Engineering and Mechanics at the University of Minnesota. He uses computational methods to study high-speed flight with application to future hypersonic flight systems and the entry of spacecraft into planetary atmospheres. Candler and his research collaborators have developed widely-used computational methods and codes that are being used for the design and analysis of future hypersonic flight systems, including several NASA exploration missions. Recently, his work has focused on the development of high-accuracy simulation methods for the exploration of hypersonic flight system design space. He has published extensively in the areas of computational methods, high-temperature gas dynamics, boundary layer laminar to turbulent transition, and validation of computational simulations with hypersonic wind tunnel data. He is a Fellow of the AIAA and a member of the National Academy of Engineering. Candler received his undergraduate degree from McGill University and his graduate degrees in Aeronautics and Astronautics from Stanford University.