Roughness-induced transition is an unavoidable reality in practical high-speed vehicles. Typical prediction of transition due to roughness include algebraic correlations and, more recently, semi-empirical methods. In the NASA Langley Research Center Supersonic Low Disturbance Tunnel, a Mach 3.5 quiet tunnel, several transition experiments have been performed in the past decade to better understand the mechanisms by which small roughness causes transition in a supersonic boundary layer. The study started first with isolated roughness elements of different planforms and shapes and progressed to increasingly more complicated geometries before arriving at a pseudorandom roughness, defined by an analytic function. Concurrent computational efforts progressed with these studies as well, starting with the use of linear stability theory and progressing to the use of harmonic linearized Navier-Stokes to predict the growth of boundary layer stabilities.

Dr. Amanda Chou is a research aerospace engineer at the NASA Langley Research Center in the Flow Physics and Control Branch. Her research focuses primarily on high-speed boundary layer transition and receptivity to freestream disturbances. Dr. Chou earned her Bachelor of Science in Honors in Aerospace Engineering from Virginia Tech and her Master of Science and Doctorate in Aeronautics & Astronautics from Purdue University.