Effect of multiple Görtler vortices on roughness-induced transition in a high-speed boundary layer

The impact of Görtler vortices on roughness-induced transition in a Mach 6 concave hypersonic boundary layer is examined through implicit large eddy simulation. Our prior numerical investigations indicated that the evolution of the most amplified Görtler vortices appeared to have minimal influence on the process of roughness-induced transition within a hypersonic boundary layer. In this study, we conduct a comprehensive analysis of the effects of Görtler vortices on roughness-induced transition by simulating various roughness locations, dimensions, and multiple Görtler vortices. In hypersonic flows, the trapped layer Görtler mode is predominant; however, the most amplified Görtler vortices exhibit negligible influence on roughness-induced vortices, regardless of whether the roughness location or dimension is altered. This behavior contrasts sharply with that observed in other Görtler vortices. Amplified Görtler vortices with a wavelength twice that of the most amplified Görtler vortices significantly affect roughness-induced vortices and delay the transition process. It appears that distinct Görtler vortices exert varying degrees of influence on roughness-induced transition.