40th NIA CFD Seminar: Non-equilibrium Pressure Considerations in Modeling Viscous Rotating Flows
Speaker: Robert L. Ash
Biography: Dr. Robert L. (Bob) Ash joined the engineering faculty at Old Dominion University at the time when LaRC was heavily involved in the design and development of their spectacularly successful Viking missions to Mars.
His research has been sponsored primarily by NASA, and accomplishments have ranged from co-inventing riblets for turbulent skin friction drag reduction through determination that the most cost-effective and practical way to accomplish sample return and human missions to Mars was to manufacture the rocket propellant required for the return trip in situ using local Mars water and carbon dioxide (while he was working as a National Research Council Senior Resident Researcher at JPL). He and now-retired LaRC scientist, Dr. Allan J. Zuckerwar, have been collaborating for more than 30-years, working to develop a better understanding of the role of bulk viscosity in modeling fluid behavior, and that effort has led to the work that will be discussed in this seminar. Professor Ash is designated as an Eminent Scholar in the Mechanical and Aerospace Engineering Departmetn at Old Dominion University.
Abstract: Hamilton's Principal of Least Action has been employed to incorporate non-equilibrium fluid behavior in the study of simple viscous flows. The original goal was to clarify the role of bulk viscosity in modeling high-speed viscous and reacting flows. The theory demonstrated that bulk viscous transport effects and non-equilibrium density effects coexisted, but were intertwined. Employing acoustically-based estimates for this overall bulk viscous effect, the theory predicted correctly the density-jump and shock thickness for air flows at various Mach numbers. The theory also exhibited a separate non-equilibrium pressure effect, and the associated pressure relaxation coefficient could be estimated using acoustic data. Recently-published work has identified a possible new low-speed sound source, while predicting that pressure deficits within the central cores of tornadoes and dust devils (and similarly aircraft trailing line vortices) can be substantially larger than equilibrium-based estimates. Modifying the Navier-Stokes equations to incorporate non-equilibrium.......
Additional information, including the webcast link, can be found at the NIA CFD Seminar website, which is temporarily located at: