The effects of stagnation enthalpy on a hypersonic boundary layer developing over a compression ramp are analyzed in this work using direct numerical simulations. Separate sets of simulations with different values of free-stream temperature, wall-cooling rate, and edge Mach number are carried out to evaluate and isolate stagnation enthalpy effects. Moreover, these sets of calculations are performed with and without vibrational excitation to further characterize the impact of this thermodynamic phenomenon on the flow. The presented calculations show that the variation of stagnation enthalpy and the presence of vibrational excitation are not able to qualitatively alter the structure of the flow. From a quantitative point of view, it is shown that the variation of the thermodynamic state of the gas can cause a 10% variation in the skin-friction coefficient, a 20% decrease in wall heat flux, and a shift in the typical frequencies of wall-pressure fluctuations by a factor of 2 toward higher frequencies.

• Received 19 October 2023
• Accepted 15 February 2024

DOI:https://doi.org/10.1103/PhysRevFluids.9.033401