Development of a hybrid DSMC/Navier-stokes solver with application to the STS-119 boundary layer transition flight experiments

K. A. Stephani, D. B. Goldstein, P. L. Varghese

Research output: Contribution to conferencePaper

Abstract

The effects of rarefaction on hypersonic boundary layer flow over a discrete surface roughness element are examined in the context of the STS-119 flight experiment. The purpose of this flight experiment was to acquire data regarding the onset of roughnessinduced boundary layer transition during atmospheric entry of the Orbiter. Transition onset was confirmed at a freestream Mach number M = 15.1 Initial estimates indicate that the local Knudsen number (Kn = λ/k) in the region of the roughness was O(10-3), such that k ∼ 450λ, where k is the height of the protuberance and λ is the molecular mean free path. In this regime, the continuum approximations of zero velocity and no thermal slip at the wall begin to break down, and thermal non-equilibrium effects may become more prominent due to a relative increase in time required for thermal equilibration. The aim of this work is to address the significance of rarefaction effects in modeling the disturbance field generated by hypersonic boundary layer flow over surface roughness using a hybrid of the DAC and DPLR numerical simulation codes. A new method for generating DAC particles from a non-equilibrium surface reservoir is presented, and we also outline a method for matching the transport properties between the DAC and DPLR solvers. Studies have been conducted to examine flow over the STS-119 boundary layer trip geometry under flight conditions at M = 20.3. A comparison of the flowfield quantities between the hybrid and DPLR solutions indicate good agreement in the general shock structure and expansion formed in the region of the roughness, and it was also observed that the disturbances of the flowfield quantities in the wake tend to be more pronounced in the DPLR solution. The heat flux on the surface of the protuberance and the surface downstream of the protuberance is also examined. Both solvers show a significant heating augmentation on the protuberance itself, with a band of high surface heating which originates from the protuberance leading edge and extends downtream. Results from this study indicate that the Navier-Stokes solution predicts a peak heating on the roughness which is 6 times that of the undisturbed surface heating, while the vortex heating in the wake produces an increase in heating which is 3 times greater than the undisturbed surface heating. In contrast, the hybrid solution predicts a peak heating on the protuberance which is 4.5 times that of the undisturbed surface heating, while the vortex heating in the wake increases the surface heating to 1.5 times that of the undisturbed surface heating.

Original languageEnglish (US)
StatePublished - Dec 6 2011
Externally publishedYes
Event49th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition - Orlando, FL, United States
Duration: Jan 4 2011Jan 7 2011

Other

Other49th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition
CountryUnited States
CityOrlando, FL
Period1/4/111/7/11

ASJC Scopus subject areas

  • Aerospace Engineering

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    Stephani, K. A., Goldstein, D. B., & Varghese, P. L. (2011). Development of a hybrid DSMC/Navier-stokes solver with application to the STS-119 boundary layer transition flight experiments. Paper presented at 49th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition, Orlando, FL, United States.