Effect of Vibrational Nonequilibrium on Hypersonic Double-Cone Experiments

TLDR

Numerical simulations of hypersonic double‑cone experiments overpredict the heat‑transfer rate to the model by about 20%. The study aims to explain this 20% overprediction of heat‑transfer in hypersonic double‑cone simulations. The authors conduct a systematic analysis of the experimental facility and perform nozzle‑field simulations to investigate vibrational nonequilibrium effects in the test section. The simulations show that vibrational mode freezing near the nozzle throat and weak vibrational energy accommodation at the surface reduce heat transfer, and when combined with minor flow nonuniformity, the predicted heat‑transfer rate matches experimental measurements.

Abstract

Recent numerical simulations of hypersonic double-cone experiments overpredict the heat-transfer rate to the model by about 20%. We present a systematic analysis of the experimental facility and the physical modeling to explainthisdiscrepancy.Nozzlee owe eldsimulationsareusedtoinvestigatetheeffectofvibrationalnonequilibrium in the test section. These simulations show that the vibrational modes of the nitrogen gas freeze near the nozzle throatconditions, resulting inanelevated vibrationaltemperatureinthetestsection. Thislowersthekineticenergy e ux, reducing the heat transfer to the model. The effect of slip boundary conditions is also studied, and it is shown that weak accommodation of vibrational energy at the surface further reduces the heat-transfer rate to the model. The combination of these two effects brings the predicted heat-transfer rate into agreement with the experiments. In addition, weak e ow nonuniformity in the test section is shown to slightly modify the predicted separation zone, further improving the agreement.