Abstract
Due to the difficulty and expense of obtaining experimental measurements for hypersonic gas flows, numerical simulation of these flows plays an important role in the development and analysis of high speed flight vehicles. While hypersonic flow simulations have been employed in vehicle development programs since at least the 1960s, the accuracy and utility of simulation results have greatly improved over the past several decades. In recent years, with advances in both computing power and modeling techniques, simulation capabilities have increased to a point at which molecular-scale hypersonic flow phenomena can be modeled with very high fidelity for practical engineering applications. As one example of such phenomena, continuum breakdown effects associated with nonequilibrium distributions of gas molecule velocities may be important in a wide variety of hypersonic flows, and consideration of these effects becomes important in determining aerodynamic and aerothermal properties of many vehicle systems.

This talk focuses on recent efforts within the Air Force Research Laboratory (AFRL) to develop and apply numerical simulation techniques which accurately account for continuum breakdown effects in hypersonic flow regimes. Simulations employ a new AFRL code based on the direct simulation Monte Carlo (DSMC) method. In DSMC calculations, a large number of simulated particles – each representing many individual atoms or molecules – are tracked through a computational grid, and probabilistic routines are used to model collisions between nearby particles. Applications covered in the talk include assessment of continuum breakdown effects and uncertainty quantification in shock wave-boundary interaction flows, as well as aerodynamic optimization for a lifting reentry vehicle. Recent DSMC algorithm development work at AFRL will also be discussed, with a focus on efforts to greatly reduce computational expense in hypersonic flow simulations at comparatively low altitudes.

Bio
Jonathan Burt is a research engineer at the Ohio Aerospace Institute, working as a contractor in the Aerospace Systems Directorate of the Air Force Research Laboratory (AFRL) at Wright-Patterson Air Force Base. His work includes development of a direct simulation Monte Carlo (DSMC) code which is currently used for hypersonics and space systems applications by AFRL, NASA and other government agencies. Additional work in this position includes aerodynamic analysis for Air Force flight test programs and algorithm development for rarefied gas flow simulations. Before coming to AFRL in 2010, he work as a post-doctoral researcher at the University of Michigan, where his research focused on multiscale simulation of atmospheric reentry and rocket exhaust flows. He received a PhD from the University of Michigan in 2006 and a BS from Yale University in 2001.

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