Advanced validation of nonequilibrium plasma flow simulation for arc-heated wind tunnels

Turbulent plasma flows in arc heaters, such as Japan Aerospace Exploration Agency's 750 kW, NASA's 20 MW, and Kyushu University's 20 kW facilities, were investigated, and the distributions of the flowfield properties were successfully obtained. The arc discharge in the constrictor section and the expansion processes in the nozzle section played key roles in the formation of an arc-heated flow. Hence, for accurately predicting high-enthalpy flow properties, it was important to correctly model the complex phenomena observed in various-scale facilities. For this purpose, an integrated analysis model to simulate various-scale arc-heated flows with high accuracy was developed. The turbulent flowfield was described using the Reynolds-averaged Navier-Stokes equations with a multitemperature model, which was tightly coupled with electric-field and radiation-field calculations. A sophisticated and low-cost radiation model and a low-Reynolds-number two-equation turbulence model were introduced into the flowfield simulation. To validate the present integrated analysis model, the computed results were compared with the corresponding experimental data for the mass-averaged enthalpy, the translational and rotational temperatures, and the number density of nitrogen obtained through spectroscopic and laser-induced fluorescence techniques. Moreover, the mechanisms of energy input by discharge and energy loss are discussed, along with the distributions of the electronic excitation temperature and heat flux on the constrictor wall derived from the arc column. Although the results indicated that a relatively detailed discharge model is required to describe the arc discharge with relatively high accuracy, the present flowfield model was generally in good agreement with various operating conditions of the facilities.