Wavy surface induced transition delay for various controlled breakdown scenarios in supersonic boundary layers

The impact of wavy surfaces on the transition processes for various controlled breakdown scenarios was investigated using numerical simulation in a Mach 4.5 boundary layer. The transition scenarios were compared between the smooth wall case and the wavy wall cases. The findings revealed that wavy surfaces have the potential to delay transition in high-speed boundary layers, regardless of whether it is the subharmonic breakdown scenario, the fundamental breakdown scenario, or any other breakdown scenario examined in this study. The presence of wavy surfaces dampens forced planar second mode disturbances with high frequencies, whereas lower frequency oblique first mode disturbances remain unaffected by the wavy surfaces. Although certain high-frequency oblique disturbances are excited by the wavy surfaces, their growth does not persist over a significant distance. The wavy surfaces modify the development of disturbances, thereby altering the flow stability. This research proposes an effective flow control strategy utilizing wavy surfaces to delay transition in supersonic boundary layers.