Study of shock-shock interactions for the HET facility double wedge configuration using the DSMC approach

Abstract

A set of numerical simulations designed to study the laminar, shock-shock interactions from hypersonic flows about a double-wedge configuration for the Hypervelocity Expansion Tube (HET) facility are presented. Computations are made using the Direct Simulation Monte Carlo (DSMC) method, an approach for modeling finite-Knudsen number flows. The current study focuses on the investigation of Mach 7 nitrogen flows about a 30-/55-deg double wedge model for stagnation enthalpies varying from 2.0-8.0 MJ/kg. The simulation results of the double wedge flows are compared with the data obtained from experiments at HET. Numerical Schlierens are generated to visualize the shock structure and shock-shock interactions present in these flows and are compared with the experimental Schlieren images. The computed heat transfer values from the simulations match the experiment along the first surface, but on the second wedge the computed heat transfer distribution over predicts the measured peak values. The influence of different models for nonequilibrium nitrogen dissociation, rotational and vibrational relaxation rates, and gas-surface interactions on the shock interaction region are analyzed for high enthalpy flow features and heat transfer rates. Overall good agreement is observed in the experimental and computational results. Unsteadiness of the flow and time-averaging of the experimental measurements are likely reasons for the inability of the DSMC simulations to exactly reproduce the experimental data.

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