When
Thursday, October 30, 2025 at 4:00 P.M.
Koen Groot
Assistant Professor
Mechanical Engineering
University of Wyoming
"Crossflow-Vortex/Step-Excrescence Interaction: How A Step Can Postpone Laminar-Turbulent Transition"
AME Lecture Hall, Room S202
Zoom link
Abstract: Instability mechanisms drive laminar flows to transition to turbulence, which contributes high drag in commercial flight and high heating in hypersonic conditions. The crossflow instability mechanism, for example, is most relevant in flows subject to high sweep and yields stationary, streamwise vortices that distort the laminar boundary layer. An interesting situation occurs when these vortices run over step excrescences, which naturally occur when wing panels are not perfectly flush and when the thermal protection system on hypersonic vehicles undergoes an uneven thermal expansion. While transition to turbulence occurs at the step when the step height is large enough, small step heights have been demonstrated to be able to postpone transition in low-speed conditions versus the "clean case", i.e. without a step. Dr. Groot will explain how this is possible and how he plans to investigate crossflow-vortex/step-excrescence interaction at hypersonic conditions.
Bio: Koen J. Groot is an assistant professor at the University of Wyoming, he specializes in theoretical and computational aerodynamics and focuses on flow instability mechanisms. He was recently awarded the Top Prof award for exceptional contributions to the University of Wyoming and service to the students in Spring 2025, notably this is less than one year after he started his position in Wyoming; and he was awarded the Texas A&M University Engineering Teaching Excellence Award in Spring 2024. Notable accomplishments include successfully extracting secondary crossflow instability information from a base flow measured by tomographic Particle Image Velocimetry (tomo-PIV) and helping achieve laminar flow on a Slotted Natural-Laminar-Flow (SNLF) wing in the NASA Ames 11-foot transonic wind tunnel as contributor to a NASA University Leadership Initiative (ULI). He completed his PhD degree in aerospace engineering at Delft University of Technology.