Search

In the paper (Theoret Comput Fluid Dyn 36:705–722, 2022), we analyzed acoustic receptivity of the boundary layer on a flat plate in Mach 6 flow at various angles of attack (AoA). It was shown that slow and fast acoustic waves passing through: a bow shock at AoA = - 5 ∘ , a weak shock induced by the viscous–inviscid interaction at AoA = 0 ∘ , or an expansion fan at AoA = 5 ∘ , excite dominant modes F and S in a small vicinity of the plate leading edge. The present paper extends this analysis to the cases of receptivity to entropy and vorticity waves. Similar to the case of acoustic receptivity, modes F and S of about equal amplitude are excited in a small vicinity of the plate leading edge. These modes propagate downstream in accord with the two-mode approximation model accounting for the mean-flow nonparallel effects and the intermodal exchange mechanism. Cross-comparisons of the initial amplitudes of excited modes help to evaluate the relative role of acoustic, entropy and vorticity waves in the second-mode dominated transition. [ABSTRACT FROM AUTHOR]

Direct numerical simulation and theoretical analysis of acoustic receptivity are performed for the boundary layer on a flat plate in Mach 6 flow at various angles of attack (AoA). Slow or fast acoustic wave passes through: a bow shock at AoA = - 5 ∘ , a weak shock induced by the viscous–inviscid interaction at AoA = 0 ∘ or an expansion fan emanating from the plate leading edge at AoA = 5 ∘ . The study is focused on cases where the integral amplification of unstable mode S (or Mack second mode) is sufficiently large (N ≈ 8.4) to be relevant to transition in low-disturbance environments. It is shown that excitation of dominant modes F and S occurs in a small vicinity of the plate leading edge. The initial disturbance propagates further downstream in accord with the two-mode approximation model accounting for the mean-flow nonparallel effects and the intermodal exchange mechanism. This computationally economical model can be useful for predictions of the second mode dominated transition onset using the physics-based amplitude method. [ABSTRACT FROM AUTHOR]