26 July 2008

Impinging shock results for a 5 degree wedge at Mach 8.2

After a dead-end-full month of futzing with Gridgen, DPLR, and Tecplot 360, today I finally got a result worth showing:

This is a simulation of a hypersonic experiment performed by Kussoy and Horstman in 1991. A flat plate and an angled wedge are placed in a Mach 8.2 flowfield. Starting from the upstream tip of the flat plate (not shown), a turbulent boundary layer develops along the plate's length. An attached shock occurs at the wedge tip, and the shock interacts with the plate's turbulent boundary layer. Kussoy and Horstman looked at how surface pressure and heat flux at the plate varied with the wedge angle. Here I'm comparing their surface pressure data with my simulated numbers for the 5 degree wedge case. Agreement isn't that bad (eyeball norm), especially given the paper's experimental error bounds and how new I am to this whole process.

I was surprised to see the simulated pressure gradient is sharper than the experimentally obtained gradient. I suspect that

  • I goofed when specifying the turbulence transition point along the flat plate, or
  • perfect air assumptions weren't appropriate, or
  • Baldwin-Lomax wasn't the right turbulence model to use, or
  • I've not done any averaging and the flowfield has turbulence, or
  • any one of a number of other things.
I'm elated to be in the why-isn't-this-what-I-expect stage instead of playing the why-is-the-solver-blowing-up game.

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