Guest editorial: Special issue on measurement, modeling and prediction of hypersonic turbulence

Modern developments in materials science, propulsion, and aerothermodynamics pave the way for hypersonic transport. However, the design of vehicles that operate in the hypersonic regime is challenging. In particular, aerodynamic heating rates enhanced by boundary layer turbulence and thermo-chemical effects significantly challenge the structural integrity of high-speed vehicles. Overly conservative design decisions will increase vehicle mass, drastically reducing the available payload size and deployment options. Despite the challenging effects, turbulent boundary layers are often inevitable or even desired, for instance, in scramjet-relevant applications. Despite the critical importance of aerothermal heating, significant discrepancies between predicted and measured turbulent aerodynamic heating and drag over high-speed bodies are reported. These discrepancies warrant an urgent development and improvement of multi-fidelity computational models to enable hypersonic vehicle design and optimization. However, the experimental and numerical database for turbulent flows above Mach 5, critical for predictive model validation, remains exceptionally scarce. The available data are almost entirely restricted to perfect gas flows, leaving a significant gap in our understanding of how high-temperature effects impact turbulence. Ultimately, the guest editors are convinced that progress in the fundamental understanding of hypersonic turbulence can only occur through a synergistic effort among world-renowned scientists in the field. This will improve the state of the art in prediction capabilities and hence allow for a more effective vehicle design from an aerodynamic and, thus, systems perspective.