Passive porous coating effect on a hypersonic boundary layer on a sharp cone at small angle of attack

Abstract: Experimental investigations are performed to understand the effect of the passive porous coating on the high-frequency disturbances and laminar–turbulent transition of a hypersonic boundary layer on the sharp cone with an apex half-angle Θ_c = 7° aligned at normalized angles of attack up to α = 1° at the Mach number M_∞ = 5.8. It is demonstrated that the passive porous coating effectively suppresses the most unstable second-mode disturbances in the hypersonic boundary layer at the studied angles of attack. It is found that the passive porous coating delays the laminar–turbulent transition both on the windward and leeward sides. The reflection coefficient of the passive porous coating for ultrasonic acoustic waves is also measured.