Assessment of BGK Approaches to Modeling of Nozzle Flows (PREPRINT)
AIR FORCE RESEARCH LAB EDWARDS AFB CA
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Accurate and numerically efficient modeling of low to moderate Reynolds number nozzle flow expansions to vacuum can be difficult due to the presence of multiple flow length scales. Such simulations are important for the prediction of propulsive thrust as well as spacecraft contamination, both of which can be difficult to measure in ground based facilities. To that end, conical nozzle flows were studied for Reynolds numbers of 1,230 and 12,300 using the direct simulation Monte Carlo method DSMC, Navier-Stokes with velocity slip and temperature jump boundary conditions, and statistical and deterministic approaches to the solution of the BGK and ES-BGK equations. The deterministic and statistical solutions of the BGK equation were found to be in good agreement with the benchmark DSMC results. Statistical BGK and ES-BGK methods were also found to be more efficient methods than DSMC in the continuum and near-continuum regime, and more accurate than the Navier-Stokes equations in the portions of the flow with rarefaction, such as the boundary layer and the flow around the nozzle lip.
- Numerical Mathematics
- Fluid Mechanics