| Hypersonic gas flow over cones is solved using computational fluid dynamics to obtain accurate boundary layer profiles. A linear stability analysis is performed on the profiles to determine the amplification rates of naturally occurring disturbances, and this information is used with the e N method to predict the boundary layer transition location. The effects of free-stream total enthalpy and chemical composition on transition location are studied to give a better understanding of recent experimental observations. Namely, there is an increase in transition Reynolds number with increasing free-stream total enthalpy, and this increase is greater for gases with lower dissociation energies.; It was observed that as the free-stream enthalpy is increased, the presence of chemical reactions and translational-vibrational energy exchange in the boundary layer becomes increasingly important and a stability code which does not take these effects into account will not give correct disturbance amplification rates. However, when these energy transfer modes are properly accounted for, linear stability predicts the same trends that were observed in the experiments. The analysis demonstrates a significant damping effect of endothermic chemical reactions and thermal energy transfer in boundary layer disturbances. Conversely, exothermic reactions are shown to have a destabilizing effect. Therefore, a series of numerical experiments were performed in an attempt to further our understanding of the role of thermochemical interactions in hypersonic boundary layer stability. |
