Experimental study on hypersonic crossflow instability over a swept flat plate by flow visualization

An experimental study on the traveling crossflow instability over a 60 $$^\circ $$ swept flat plate was conducted. The Mach number is 6, the angle of attack of the model is 5 $$^\circ $$ . The traveling crossflow waves and the secondary instability of the traveling crossflow waves were visualized by nano-tracer-based planar laser scattering (NPLS) technique. In the spanwise NPLS images, the traveling crossflow waves appeared as regular strikes, and the secondary instability appeared as small eddies attached to strikes. The wavelet transform was used to study the wavelength contents of the traveling crossflow waves. The most amplified wavelength is stable before the secondary instability happening, which is around 12 mm at $$Re_\infty $$ = 3.45 $$\times $$ 10 $$^6$$ m $$^{-1}$$ . Besides, the Reynolds number effects on the boundary layer transition and traveling crossflow instability were discussed.