Effect of speed ratio increase on pressure measurement for hypersonic rarefied gas flows.

Rarefied aerodynamics need to be accurately estimated for planetary atmospheric entry and earth reentry missions. At Japan Aerospace Exploration Agency (JAXA), the hypersonic rarefied wind tunnel (HRWT) has been developed for rarefied aerodynamic prediction. In order to improve the prediction accuracy of rarefied aerodynamic characteristics, the determination of surface accommodation coefficients and its dependence on speed ratio is crucial. In this work, we have developed a cooling system for models using liquid nitrogen in order to improve speed ratio in HRWT. We have tested cooling pressure tube models in HRWT, and investigated the dependence of tube pressure on surface accommodation coefficients and surface temperature by carrying out direct simulation Monte Carlo (DSMC) computations. Finally, by comparing the measured pressure with the computed results, we discuss the effect of speed ratio increase in HRWT measurements. [ABSTRACT FROM AUTHOR]