Hypersonics Center receives additional support and continues to grow

The National Hypersonics Research Center was established at the University of Minnesota in 2004. Since then, the Center has developed into one of the leading academic programs in hypersonics research and education. The Center combines leading computational modeling and simulation methods with the world's premiere hypersonic testing facilities at CUBRC in Buffalo NY. The Center's primary goal is to support the nation's design of future hypersonic systems through the development of validated computational simulation methods. The Center receives its core funding from the Air Force Office of Scientific research; Minnesota Senators Norm Coleman and Amy Klobuchar helped to secure much of this support. Center research is also supported by NASA, DARPA, and Sandia National Laboratories.
During the past year, there have been some notable accomplishments by Center researchers. The HyCAUSE (Hypersonic Collaborative Austalia-United States Experiment) scramjet flight experiment was launched in Australia on a large sounding rocket. The inlet of this flight vehicle was designed by Center researchers and features a novel inward-turning design. Prior to the flight, the inlet and engine design were tested at CUBRC. This concept has the potential to be much more efficient than conventional inlets.
Another recent project involves the development of a computational method for the prediction of transition to turbulence in hypersonic boundary layers. Dr. Heath Johnson has been developing a computational simulation method (called STABL) that predicts how disturbances are amplified by hypersonic boundary layers. Once the cumulative amplification of a disturbance reaches a critical amplitude, it is assumed that the flow becomes unstable and has transitioned to turbulent flow. This computational method has been used to analyze a number of flows, including the HIFiRE Flight 1 geometry. HIFiRE is the Hypersonic International Flight Research and Experimentation program, and is a joint Australian – US Air Force program. Simulations performed by Dr. Johnson and AEM graduate research assistant Christopher Alba show excellent agreement with wind tunnel measurements. The experiment will be launched in May 2008, and the simulation tools will be critical for analyzing the resulting flight data. Center researchers are actively supporting the development of the HIFiRE Flight 5 geometry.
A new research project recently funded by NASA seeks to combine several of the simulation tools developed at the Center. The goal is to study how a hypersonic boundary layer transitions from laminar to turbulent flow using high-fidelity simulations. The concept is to use the computational methods developed by Prof. Candler’s research group to provide a high-quality laminar mean flow over a simple geometry such as a sphere-cone. Then using the STABL code, white-noise disturbances will be propagated through the flow field, and a field of physically-meaningful disturbances will be created. This information will then be fed to the simulation method developed by Prof. Mahesh’s research group, and the disturbances will be simulated as they interact with one another, go through the non-linear amplification regime, and then break down to turbulent flow. Prof. Mahesh’s methods are ideal for performing this type of simulation. The goal is to better understand the physics of the non-linear breakdown of hypersonic boundary layers, and then to provide more accurate models for predicting heat transfer rates during and after transition.
The Center activities will expand in a new direction with the addition of Prof. Thomas Schwartzentruber to the AEM faculty. Dr. Schwartzentruber's research in the simulation of low density hypersonic flows is a natural fit to the ongoing research at the Center. The use of his particle-based numerical simulation methods will allow novel studies of gas-surface interactions and detailed chemical kinetics processes that are critical to accurate predictions of hypersonic flows.

Graham Candler
Krishnan Mahesh