School of Aerospace Engineering

Gebhardt Distinguished Lecture

Hypersonic Boundary Layer Transition and the BOLT Flight Experiments

featuring

Graham Candler

University of Minnesota

October 30
11 a.m. - 12 p.m.
Guggenheim 442

About the Seminar: 

The Boundary Layer Transition and Turbulence (BOLT) sounding rocket flight experiments were designed to make detailed measurements of boundary layer transition and turbulence at hypersonic conditions. The BOLT geometry 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. 

About the Speaker: 
Professor Candler uses computational fluid dynamics to study high-temperature reacting flows and hypersonic flows, and is particularly interested in how the relaxation of internal energy modes and finite-rate chemical reactions interact with fluid motion. Applications of this work include the analysis of planetary entry spacecraft heat shields, hypersonic boundary layer transition, and the effects of chemical reactions on aerodynamics. Professor Candler works closely with experimentalists to validate high-enthalpy flow models by careful comparison to shock tunnel data. Recently, Candler's research group has been working to extend computational methods to complex geometries for application to future scramjet-powered hypersonic aircraft. These tools were used to design an inward-turning inlet for a upcoming sounding rocket flight experiment of a Mach 10 vehicle.