GALCIT Colloquium

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 simulating the effects of atmospheric turbulence and particulates will also be discussed.