Transition Onset Predictions for Oblique Breakdown in a Mach 3 Boundary Layer

摘要

Transition via oblique breakdown in a Mach 3 boundary layer was investigated using nonlinear PSE and DNS. This note focused on a comparison between the predictions based on PSE results via NASA's LASTRAC code and DNS results, extending all the way from disturbance generation to the initial stage of the breakdown process. Good agreement was found for all stages of transition, including receptivity, linear and nonlinear disturbance evolution, and the onset of the breakdown process until the mean wall shear had nearly doubled with respect to its laminar value. Hence, the PSE approach can correctly predict the transition onset via oblique breakdown. Therefore, when combined with appropriate turbulence models for transitional flow, this approach may provide a physics-based methodology for modeling the entire transition process of supersonic boundary layers. Finally, this note discussed the influence of the stationary modes [0, ±2] on the oblique breakdown process. By suppressing these modes, the distance to the transition onset location was increased by approximately 5%.