Amplification factor transport transition model for high-speed flows

A fully local amplification factor transport model is developed for high-speed transitional flows. On the basis of the approximate eN envelope method of linear stability theory, two transport equations are established to describe the evolution of amplification factors for first-and second-mode instabilities in high-speed boundary layers. An intermittency factor transport equation is then constructed based on the transported amplification factors and is coupled with Menter's k - ! shear-stress transport eddy-viscosity turbulence model. The new model is validated through several test cases under different flow conditions, including flat plates, straight and flared cones, and a double ramp configuration. Comparisons with linear stability theory and experimental data demonstrate the ability of the model to predict the transition behavior induced by first-or second-mode instabilities. The model provides a reasonable reflection of the effects of different parameters that influence transitions, including the Mach number, temperature, nose bluntness, and pressure gradient.