Instability and Transition of Hypersonic Boundary Layer on a Blunted Delta Wing

The instability and transition of hypersonic boundary layer on a blunted delta wing is performed by numerical simulation of experiments conducted in the quiet wind tunnel. Disturbances are calculated using linear stability theory to obtain the integrated disturbance growth rates and amplification factors from laminar steady base flows. Comparisons are made between the results of the stability analysis and the experimentally measured transition characteristics. The results show that the generalized inflections existing in velocity profiles reveal both the streamwise instability and crossflow instability of the boundary layer on the delta wing. In the parameter spaces of frequency and wave number, there is only one unstable region in which the first-mode and second-mode waves are integrated with each other at 0 degrees angle of attack, whereas the unstable regions of the first-mode and second-mode waves are separately distributed at angle of attack of 10 degrees. The numerically predicted N factor distribution is in good agreement with the measured transition front, and the N factor is about 3 when boundary-layer transition occurs. The low-frequency unstable waves with about 25-30 kHz play a key role in dominating the boundary-layer transition of the delta wing.