A direct numerical simulation of the interaction between a shock wave and the supersonic turbulent boundary layer in a compression–decompression corner with a fixed 24° deflection angle at Mach 2.9 is conducted. The characteristics of the shock interactions are investigated for two heights between the compression and decompression corners, corresponding to H/δref=4.25, 1.22, where δref denotes the reference turbulent boundary layer thickness. A classic shock wave/turbulent boundary layer interaction flow is reproduced in the higher case. For the lower case, the size of the separation region is significantly decreased, and the low-frequency unsteadiness is slightly suppressed in the interaction region, as assessed by analyzing the mean and fluctuating wall pressure. Flow patterns near the reattachment line show the existence of the Görtler vortices. By analyzing the curvature radius and Görtler number distribution, it was found that a strong centrifuge instability is reserved in the compression corner region and reversed in the decompression corner region due to the convex streamline curvature. The downstream flow of the decompression corner is relatively complex where the additional shocklet and new streamwise vortices are observed. A negative response mechanism is found regarding fluctuating wall-pressure signatures between the upstream and downstream of the decompression corner.
This paper performs direct numerical simulations of hypersonic boundary layer transition over a Hypersonic Transition Research Vehicle (HyTRV) model lifting body designed by the China Aerodynamic Research and Development Center. Transitions are simulated at four angles of attack: 0°, 3°, 5°, and 7°. The free-stream Mach number is 6, and the unit Reynolds number is 107 m−1. Four distinct transitional regions are identified: the shoulder cross-flow and vortex region and the shoulder vortex region on the leeward side, the windward vortex region and the windward cross-flow region on the windward side. As the angle of attack increases, the transition locations on the leeward side generally move forward and the transition ranges expand, while the transition locations generally move backward and the transition ranges decrease on the windward side. Moreover, the shoulder vortex region moves toward the centerline of the leeward side. At large angles of attack (5° and 7°), the streamwise vortex on the shoulder cross-flow and vortex region will enable the transition region to be divided into the cross-flow instability region on both sides and the streamwise vortex instability region in the middle. In addition, the streamwise vortex also leads to a significant increase in cross-flow instability in their upper region, which can generate a new streamwise vortex instability region between the two transition regions on the leeward side. Furthermore, since the decrease in the intensity and the range for the cross-flow on the windward side, the windward cross-flow region tends to become narrow and ultimately disappears.
Direct numerical simulation with up to 10×109 scale grid points based on graphics processing unit computation is carried out to investigate the bluntness effect on the hypersonic boundary-layer transition over a slender cone with zero angle of attack at Mach 6. Four cases with the nose radii of 1, 10, 20, and 40 mm are conducted, and the corresponding Reynolds number based on the nose radius varies from 1.0×104 to 4.0×105. Random disturbances with a broad spectrum of frequencies and a wide range of azimuthal wavenumbers were applied to the wall to simulate disturbances caused by wall roughness. The numerical results show that as the nose tip radius increases, the transition position gradually moves downstream with increased transition region. For the case with a nose radius of 1 mm, the flow transition and entropy swallowing occur almost simultaneously, while for other cases, the transition takes place earlier than the entropy swallowing. In consequence, the disturbance amplitude upstream of the transition in the 1 mm case is much larger than that of other cases. To further study the mechanism of the transition, the frequency spectrum analysis is carried out. It is found that all cases exhibit two characteristic frequencies within the transition region, i.e., the high frequency and extremely low frequency. Owing to the influence of the entropy layer, the characteristic high frequency of the 1 mm case is significantly higher than that of other cases. With the increase in the nose radius, the characteristic frequency of the high frequency decreases gradually.
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