Laminar-turbulent Transition with Chemical (Non-)Equilibrium in Hypersonic Boundary-Layer Flows

Computational setup for a roughness patch on a re-entry capsule

Motivation

Blunt bodies returning from space are subject to immense heat loads leading to ablation. Roughnesses on these ablating surfaces can induce laminar-turbulent transition in an otherwise laminar flow. Laminar-turbulent transition increases the heat load on the surface. This self-energizing effect can lead to a catastrophic failure of the spacecraft. The role of the chemical modelling in high-temperature boundary layers in equilibrium and non-equilibrium is the main focus of the numerical work. 

Approach to Solution

Direct numerical simulations (DNS) are conducted on national HPC facilities such as SuperMUC and HLRS. Results show that roughness wakes are subject to an increased instability in the presence of chemical reactions and non-equilibrium effects

DNS results from vortical disturbances induced by surface roughness in a reacting environment. The wake of the roughness elements becomes unstable and laminar-turbulent transition takes place.