Unsteady DSMC Simulation of blunt nose with spike at hypersonic rarefield flows
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To design an efficient ram-air intake for an air-breathing propulsion system for VLEO (Very-Low) / SLEO (Super Low) Earth Orbit satellites requires consideration of the unsteady effects in the hypersonic low-density or rarefied environment. This study aims to analyze the unsteady effects due to shock instabilities on a forward facing spike geometry attached to a flat blunt nose in low-density hypersonic flows. The Direct Simulation Monte-Carlo (DSMC) approach is used to study two flow-conditions: 1) ground test facility (V∞ = 2075 m/s, Kn = 1.4×10−3 ) and 2) at an altitude of 100 km (V∞ = 8557 m/s, Kn = 0.45) for a spiked blunt nose with flat face. It was found that gas surface interaction (specular and diffuse reflection) results in changing dynamics of flow field for both conditions. The large amplitude shock fluctuations are not observed in lower density environments as compared to continuum flow in previous literature. The diffuse reflection leads to higher drag and higher unsteadiness at Vin fty = 2075 m/s, when compare to specular reflection, while lower drag and unsteadiness at high Knudsen number case of Vin fty = 8557 m/s.
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