Motivation

High-altitude, hypersonic flows exhibit large variations in the local mean-free-path (the average distance travelled between molecular collisions). In regions where the mean-free-path becomes large (rarefied wakes) or becomes to comparable to small length scales of interest (sharp leading edges, shock waves, boundary layers, etc.), continuum assumptions inherent in CFD methods may become inaccurate. Research focuses on coupling DSMC and CFD methods within a single simulation. CFD algorithms are used to accurately and efficiently simulate continuum regions, and the DSMC method is restricted to non-equilibrium regions where increased physical refinement is required.

Results and Publications

A Modular Particle-Continuum (MPC) Method:

    Schwartzentruber, T.E., Scalabrin, L.C., and Boyd, I.D., “Multiscale Particle-Continuum

    Simulations of Hypersonic Flow over a Planetary Probe”, Journal of Spacecraft and Rockets, 2008,

    Vol. 45, No. 6, pp 1196-1206.

    Schwartzentruber, T.E., Scalabrin, L.C., and Boyd, I.D., “Hybrid Particle-Continuum Simulations

    of Hypersonic Flow over a Hollow Cylinder-Flare Geometry”, AIAA Journal, 2008, Vol. 46, No. 8,

    pp 2086-2095.

    Schwartzentruber, T.E., Scalabrin, L.C., and Boyd, I.D., “Hybrid Particle-Continuum Simulations

    of Nonequilibrium Hypersonic Blunt-Body Flowfields”, Journal of Thermophysics and Heat

    Transfer, 2008, Vol. 22, No. 1, pp 29-37.

    Schwartzentruber, T.E., Scalabrin, L.C., and Boyd, I.D., “A modular particle-continuum method

    for hypersonic non-equilibrium gas flows”, Journal of Computational Physics, 2007, Vol. 225, No. 1,

    pp 1159-1174.

    Schwartzentruber, T.E., and Boyd, I.D., “A hybrid particle-continuum method applied to shock

    waves”, Journal of Computational Physics, 2006, Vol.215, No. 2, pp 402-416.

The above publications describe in full detail the MPC method and its application to a number of flow problems. The main publication concerning the algorithm details is the 2007 Journal of Computational Physics article cited above. Current research in my group focuses on using the MPC algorithms to couple our DSMC code (MGDS) with the CFD code (US3D) developed in Graham Candler’s group in the AEM department. Some example images of US3D solutions to transitional flows are shown below (courtesy of Joe Brock). The first simply shows temperature contours for a hypersonic flow over a 3D capsule geometry (normalized by the wall temperature). The second image shows the local gradient-length Knudsen number for the same CFD solution. Regions in which this parameter rises above 0.01, such as the near wake and leeward-side boundary layer, may require DSMC simulation for accuracy.