Receptivity characteristics of a hypersonic boundary layer under freestream slow acoustic wave with different amplitudes

摘要

An unsteady hypersonic blunt wedge flowfield under freestream slow acoustic wave is solved by direct numerical simulation (DNS), and the receptivity characteristics of the boundary layer under slow acoustic disturbance with different amplitudes are analyzed. Results show that slow acoustic wave in the freestream not only has a significant effect on the aerothermodynamics characteristics of hypersonic flowfield and boundary layer, but also on the bow shock characteristics. It shows that the maximum amplitudes of the disturbance modes in the boundary layer are positively correlated with the disturbance amplitude of the freestream. The bigger the amplitude of the freestream disturbance gets, the earlier the high-frequency disturbance mode exists, and the stronger the high frequency interference is. The larger amplitude of freestream disturbance wave can accelerate the generation of the higher order harmonic modes in boundary layer. Furthermore, the transformation position and the times of the dominant mode in the boundary layer differ under various amplitude of freestream disturbance, and compared with the smaller amplitude's slow acoustic disturbance in the freestream, the larger amplitude disturbance can accelerate the first transformation of the dominant mode in boundary layer, and also delay its second transformation.