Abstract. This talk concentrates on the effect of chemical equilibrium and non-equilibrium on hypersonic boundary-layer transition. After an introduction on the non-equilibrium and general hypersonic effects on boundary-layers and problems encountered in hypersonic re-entry flight, two major cases are presented. First, the influence of chemical equilibrium and non-equilibrium on harmonic wave propagation in a two-dimensional flat-plate boundary layer is considered. The problems for DNS are also touched. The disturbance evolution in the presence of chemical equilibrium and non-equilibrium is elucidated.
As a second subject, the wake of a boundary-layer sized object in a hypersonic boundary layer is investigated. Paralleling the conditions of the HyBoLT-experiment, the wake of a cuboid object is simulated with DNS to investigate for the instability of the boundary-layer in the wake in the presence of chemical reactions. An outlook is given to planned activities of the group on transition investigations in high-enthalpy capsule-geometry boundary-layer flows (generic Apollo shape - Orion).