Computational Hypersonics Research Lab
Director G. Candler
Location: 230 Akerman Hall

Computational Hypersonics Research LabDirector G. Candler Location: 230 Akerman Hall The Computational Hypersonics Research Lab is developing computational fluid dynamics methods and simulation tools for the design and analysis of future hypersonic flight systems. Graham Candler leads the research group, in close collaboration with the Nichols and Schwartzentruber research teams at the University of Minnesota. The research is supported by the Air Force Office of Scientific Research, the Office of Naval Research, the Air Force Research Laboratory, Sandia National Laboratories, and NASA. The overall goal of the Lab is to develop physicsbased models and highfidelity numerical methods to predict the operation of hypersonic flight vehicles and to discover new hypersonic flow physics. The main tool is US3D, which is a highly parallel, implicit, unstructured grid code designed for the simulation of complexgeometry hypersonic flow fields. Simulations can be performed with conventional secondorder upwind numerical methods and highorder, lowdissipation methods. This enables rapid solutions for steadystate problems, and the simulation of more complex flows that require the resolution of finescale features or unsteady effects. Thus, the US3D code can be used to simulate fullvehicle configurations to predict aerodynamics and aeroheating, but it can also be used in largeeddy simulation (LES) or direct numerical simulation (DNS) mode to resolve complicated flow physics. A complete set of finiterate chemical kinetics models for hightemperature air are included, and novel loworder manifold approaches are being developed for the simulation of highspeed scramjet combustor flows. One of the primary areas of focus in the Lab is on predicting how hypersonic boundary layers transition from a laminar state to a turbulent state. Understanding this process is critical because transition to turbulence typically increases the heat transfer rate to the surface by a factor of three to eight. Transition prediction is usually performed with linear stability analysis methods, in which an assumed disturbance mode is tracked through the laminar flow field and the rate of growth of the disturbance is computed. Then, when a specified relative amplitude is reached, the boundary layer is predicted to be critically unstable, leading to transition to turbulence. Such an approach has been shown to work for simple hypersonic flows like sharp cones at zero angle of attack, but it becomes increasingly inaccurate as the geometry becomes more complicated. At the University of Minnesota, we have been using the advanced simulation methods in US3D to explore more general approaches to predicting transition, including using methods from the linear systems literature and direct numerical simulations on very large grids with highorder numerical methods. The figures below show the results of a 160 million grid element solution on the AFOSR Boundary Layer Transition (BOLT) sounding rocket hypersonic flight experiment; Figure 1 shows the surface heat transfer rate, and Figure 2 visualizes instabilities that grow in the BOLT flow field. These simulations are being compared with experiments; so far, everything is consistent with the data. AFOSR Boundary Layer Transition (BOLT) Sounding Rocket Hypersonic Flight Experiment
The research is also developing advanced physicsbased models for hightemperature air reactions, novel finiterate kinetics models for carbon oxidation and ablation, new approaches for representing turbulence at extreme conditions, and the ability to simulate the interaction of particulates in the freestream with the flow field. The US3D code is being combined with the Molecular Gas Dynamics Simulator (MGDS) code being developed in the Schwartzentruber group to predict hypersonic flows at conditions where the continuum NavierStokes equations are not valid. Recent simulations of highspeed combustion with inexpensive loworder manifold approaches to represent the combustion process show promise for the development of predictive simulations of scramjet flowpaths. Last Modified: 20181220 at 09:37:11  this is in International Standard Date and Time Notation 