Key scientific questions

Two key scientific questions arise in this context:

"How does increasing stagnation energy modify the coupling between turbulence, shocks, and thermochemical nonequilibrium processes in high-speed flows?"

In homogeneous isotropic turbulence, increasing stagnation energy promotes the onset of chemical dissociation and vibrational excitation. These phenomena may be triggered both by turbulence fluctuations and shock-induced compression, with characteristic timescales that can become comparable to those of the turbulence, leading to strongly non-equilibrium flows. Because of the highly nonlinear coupling between turbulence, thermochemistry, and shock dynamics, modeling remains a major challenge for turbulence models.

In wall-bounded configurations, additional mechanisms influence the interaction, including wall cooling and surface chemistry. In particular, the intense heat fluxes associated with shock-wave/boundary-layer interactions can give rise to significant conjugate heat transfer effects, which may alter the structure and dynamics of the interaction. Understanding the fundamental implications of these processes and their representation in reduced-order models is therefore a central question for the colloquium.

"What are the governing drivers of hypersonic shock–turbulence interactions across the parameter space?"

Hypersonic shock–turbulence interactions span a wide parameter space defined by turbulence intensity, Mach number, wall cooling, and thermochemical conditions. Exploring this space enables the identification of distinct interaction regimes and the dominant mechanisms governing each of them.

In homogeneous turbulence, parameter variations influence the relative importance of vortical, dilatational, and entropic fluctuations, as well as their coupling with shock dynamics and chemical non-equilibrium processes. In wall-bounded configurations, wall temperature, surface characteristics, and inflow turbulence determine separation behaviour, heat transfer, and pressure fluctuations, which are also coupled with non-equilibrium phenomena. Hence, establishing the governing influences across these parameters is crucial for enabling meaningful comparisons between different flow configurations, as well as between experimental and numerical studies, where boundary conditions and external constraints may differ, and therefore represent a key topic for discussion in the colloquium.