Improved modeling of blow-down supersonic wind tunnels

Supersonic wind tunnels are an essential tool for high-speed aerodynamics research, supporting studies ranging from fundamental flow analysis to advancements in supersonic transport. Accurately predicting tunnel performance, however, requires precise mathematical modeling. Previous models have primarily focused on plenum pressure predictions, often assuming an adiabatic process and overlooking temperature dynamics. Temperature changes during a test affect velocity and Reynolds number, influencing experimental measurements and underscoring the need to improve temperature prediction capabilities. In this paper, we develop a new model introducing two key corrections: heat addition from the thermal mass of the wind tunnel and real gas effects, particularly the Joule–Thomson effect, allowing us to capture the critical influence of temperature. Additionally, we account for pressure losses within the piping system. Comparative analysis with experimental data shows that our model reduces temperature prediction errors to within 2%, a marked improvement over the base model’s 9–13% error range. Furthermore, pressure predictions are refined, yielding more accurate assessments of plenum, reservoir and valve inlet pressures. These findings underscore the model’s utility in enhancing control system development and its broader value in advancing experimental design and operational precision in supersonic wind tunnel research.