A recent numerical study by Huang et al. [“The stabilizing effect of grooves on Görtler instability-induced boundary layer transition in hypersonic flow,” Physics of Fluids, Vol. 35, No. 4, 2023, Paper 041701] has shown that grooves can attenuate secondary instability of Görtler vortices when placed at the center of Görtler streaks (the groove valley location coincides with the low-speed streak location) over a concave wall. However, experimental studies have not been conducted, and the underlying physical mechanism has not been investigated. For that reason, calculations are performed based on direct numerical simulations and biglobal stability analysis to discover the delaying mechanism. In the simulations, Görtler vortices are excited by wall steady blowing and suction with spanwise wavelengths of 3 mm. The wall is covered with grooves with depths in 1, 2, and 3 mm. A delaying mechanism by grooves is proposed: grooves with spacings corresponding to the wavelength of primitive Görtler vortices reduce the streamwise velocity gradients, which act as the source of the disturbance energy. Thus, the growth rate of the sinuous secondary instability mode of Görtler vortices is reduced efficiently, leading to the delay of boundary-layer transition. In addition, with the increase in the depth of grooves within an appropriate range, a better stabilizing effect can be achieved. The effect of phase difference between grooves and stationary Görtler vortices on hypersonic boundary-layer transition is also investigated, revealing that grooves with 0 phase difference (i.e., the groove peak location coincides with the low-speed streak location) could delay the boundary-layer transition most efficiently. Finally, preliminary experimental results are obtained, showing a qualitative agreement with the numerical results.
Delaying Görtler-Vortex-Induced Hypersonic Boundary-Layer Transition Utilizing Streamwise Grooves
AIAA Journal ; 1-12
01.06.2025
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
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