Daniel MAURAT, Gabriel AXTMANN, Uwe GAISBAUER, Robert HRUSCHKA, Friedrich LEOPOLD
DOI Number: N/A
Conference number: HiSST-2025-057
Hypersonic test facilities are used to accelerate the fluid to the desired test conditions. Hypersonic nozzles are classically designed by using the Method of Characteristics (MoC) in combination with a boundary layer correction. However, previous studies has shown that this design method is only valid for design Mach numbers below eight, since it assumes a boundary layer that remains relatively thin compared to the nozzle radius. This assumption is no longer valid for higher Mach numbers. An alternative approach to overcome this limitation is the design-by-analysis method, which uses the results from numerical simulations of the nozzle flow to generate the nozzle contour at the desired design point. For this purpose, the framework HyNCO (Hypersonic Nozzle Contour Optimization) has been developed at the Institute for Aerodynamics and Gas Dynamics, University of Stuttgart (IAG), combining numerical simulations with a multi-objective genetic optimization approach to generate a group of optimized nozzle contours. To obtain accurate and reliable results, selecting the appropriate numerical setup is crucial. The choice of gas model significantly influences the simulation’s precision and computational efficiency. Therefore, a numerical study has been conducted consisting of three cases: thermally and calorically perfect gas with a range of constant isentropic exponents, real gas as one species with an temperature dependent isentropic exponent and a gas in thermochemical non-equilibrium. These results were compared with experimental results obtained at the STB shock tunnel at French-German Research Institute of Saint-Louis (ISL) for a nozzle with exit Mach number of Me = 8. Among the numerical cases, the thermochemical non-equilibrium model provided the closest reproduction of the experimental results. However, its high computational effort makes it impractical for the optimization process. On the other hand, the case using a constant isentropic exponent also agrees well with the experimental data while requiring significantly less computational effort. It is therefore the preferred choice for nozzle optimization. Based on this study, a nozzle contour optimization with HyNCO for the Mach 8 nozzle at the STB shock tunnel is conducted. In addition to the nozzle flow, the thermal and mechanical loads on the nozzle are evaluated with regards to the possibility of modular nozzles and different materials for the nozzle wall.