A numerical investigation of supersonic nozzle boundary layer transition

It has been found in previous studies that the wall heat flux measured experimentally in the NASA Lewis high-area-ratio nozzle was not always predicted by laminar or turbulent boundary layer computations. These results suggest that the boundary layer undergoes transition. In the present paper, the e^N method was used to predict which operating conditions produce boundary layer transition In the nozzle. If transition was predicted, the stability analysis provided the location of transition onset as well as the structure and wavelength of the dominant instability. Tollmien-Schlichtingwaves and Taylor-Görtler vortices were considered as possible disturbance structures which trigger transition. When the chamber pressure was 360 psia, the stability analysis indicated that transition does not occur in the nozzle. The analysis correctly determined that a laminar boundary layer computation accurately predicts the experimental wall heat flux. For chamber pressure of 656 psia and above, it was found that Taylor-Gortler vortices produced transition in the nozzle. At these conditions, the laminar boundary layer computation did not accurately predict the wall heat flux. The stability analysis can be used to establish the nozzle conditions which will be accurately predicted by a laminar boundary layer computation.