High-enthalpy shock/boundary-layer interaction on a double wedge

Jean-Paul Davis, Caltech

Interaction between a shock wave and a boundary layer at a compression corner can produce a region of separated flow, the size of which is important in determining aerodynamic forces. Real gas effects (e.g., in a high enthalpy dissociating flow) on the length of the separated region are not well known. Experiments to measure separation length are performed in the T5 Hypervelocity Shock Tunnel on a double wedge configuration with nitrogen test gas. The double wedge geometry allows greater control over local flow conditions at separation and, at high incidence angle, can produce stronger real gas effects due to dissociation behind the leading shock. Local flow conditions at separation are found by computational reconstruction of the external nonequilibrium flow field. Analysis of separation length for a laminar non-reacting boundary layer leads to a new scaling based on triple-deck theory, extending a previous result to arbitrary viscosity law and non-adiabatic walls. A classification is introduced which divides mechanisms for real gas effects into mechanisms acting internal and external to the boundary layer. External mechanisms are shown to decrease separation length in high enthalpy dissociating flows. Internal mechanisms are considered qualitatively. A limited numerical study shows that internal mechanisms for real gas effects are relatively unimportant in the present experiments. Correlations are presented of experimentally measured separation length against reattachment pressure ratio and Reynolds Number using the new scaling law (which includes external mechanisms for real gas effects). Real gas effects on reattachment heat flux will also be discussed.

For more details, see my ISSW 21 paper.

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