Distance Of Shock Wave Research Articles

On low-frequency unsteadiness of single-incident and dual-incident shock waves/turbulent boundary layer interactions with large-scale separations

Interactions between turbulent boundary layer and single-incident or dual-incident shock waves are commonly observed in supersonic inlets. To provide novel insights into the unsteadiness of these interactions, six incident shock wave/turbulent boundary layer interactions (ISWTBLIs), including both single-ISWTBLIs and dual-ISWTBLIs, are experimentally investigated using dynamic wall-pressure measurements at Mach 2.73 flow conditions. Through spectral analysis and correlation analysis, the unsteadiness characteristics of single-ISWTBLIs and dual-ISWTBLIs are comparatively examined, revealing significant influences of shock-wave strength and shock-wave distance on low-frequency unsteadiness. Specifically, both regions near the separation and reattachment points exhibit distinct low-frequency unsteadiness in single-ISWTBLIs and dual-ISWTBLIs with relatively strong separations. An increase in the deflection angle from 10° to 12° in single-ISWTBLIs extends the streamwise separation length, while causing a dramatic decrease in both characteristic frequency and normalized characteristic frequency (Strouhal number) of low-frequency unsteadiness. However, for dual-ISWTBLIs, as the shock-wave distance increases, there is an initial increase followed by a subsequent decrease in the separation length accompanied by a continuously increasing characteristic frequency, thus indicating a different relationship between separation length and characteristic frequency of unsteadiness in dual-ISWTBLIs in comparison with that observed in single-ISWTBLIs. Moreover, correlation analysis revealed that the pressure signals in the reattachment region are of strong negative correlation with those near the separation-shock foot, and the correlation increases with increasing shock-wave strength in single-ISWTBLIs and decreasing shock-wave distance in dual-ISWTBLIs.

Separation length scaling for dual-incident shock wave–turbulent boundary layer interactions with different shock wave distances

In this study, the length scaling for the boundary layer separation induced by two incident shock waves is experimentally and analytically investigated. The experiments are performed in a Mach 2.73 flow. A double-wedge shock generator with two deflection angles ( $\alpha _1$ and $\alpha _2$ ) is employed to generate two incident shock waves. Two deflection angle combinations with an identical total deflection angle are adopted: ( $\alpha _1 = 7^\circ$ , $\alpha _2 = 5^\circ$ ) and ( $\alpha _1 = 5^\circ$ , $\alpha _2 = 7^\circ$ ). For each deflection angle combination, the flow features of the dual-incident shock wave–turbulent boundary layer interactions (dual-ISWTBLIs) under five shock wave distance conditions are examined via schlieren photography, wall-pressure measurements and surface oil-flow visualisation. The experimental results show that the separation point moves downstream with increasing shock wave distance ( $d$ ). For the dual-ISWTBLIs exhibiting a coupling separation state, the upstream interaction length ( $L_{int}$ ) of the separation region approximately linearly decreases with increasing $d$ , and the decrease rate of $L_{int}$ with $d$ increases with the second deflection angle under the condition of an identical total deflection angle. Based on control volume analysis of mass and momentum conservations, the relation between $L_{int}$ and $d$ is analytically determined to be approximately linear for the dual-ISWTBLIs with a coupling separation region, and the slope of the linear relation obtained analytically agrees well with that obtained experimentally. Furthermore, a prediction method for $L_{int}$ of the dual-ISWTBLIs with a coupling separation region is proposed, and the relative error of the predicted $L_{int}$ in comparison with the experimental result is $\sim$ 10 %.

Influence of expansion corner on the interaction of dual separation zones

The complex shock waves/boundary layer interaction is an important problem in inlets, which induces the interaction of multiple separation zones and has attracted experts’ attention gradually. In this paper, based on a two-dimensional hypersonic inlet model, a numerical method is used to study the influence characteristics of the expansion corner on dual separation zones’ interaction. The shock wave distance is changed to realize the fusion of dual separation zones and the re-separation of the fused separation zone. Analyses are carried out by setting different corner angles of 0°, 2°, 5°, and 10°. The results show that with the increase in the corner angle, the maximum separation scale achieved by the fusion process gradually decreases and the flow field structures of the fusion and re-separation processes tend to be consistent in the same shock wave distance. Furthermore, given the inflow parameters, the scale change and the “hysteresis effect” of the interaction between different separation zones are weakened by the corner influence.

Computational and experimental analysis of Mach 2 air flow over a blunt body with plasma aerodynamic actuation

According to the mechanism of the arc plasma heating effect, and from a phenomenological perspective of view, the plasma actuation was simplified as heating energy injected into the supersonic flow field for the numerical research on controlling detached shock of the blunt body in non-center symmetrical positions. Besides, experimental research on the form and strength of detached shock wave control by plasma aerodynamic actuation in non-center symmetrical positions was conducted in a high-speed shock tunnel (M=2). The results showed that the detached distance of shock wave increased and the strength of normal shock wave ahead of the detached shock wave reduced when plasma actuation was applied. The control effect was greatly improved after the magnetic field was applied and the effect of upwind-direction flow was the best one. When the upwind-direction flow was applied with 1000 V voltage actuation, the distance of detached shock wave would increase from 3.4 to 7.6 mm and the time average strength of normal shock wave was weaken by 5.5%. At last, the mechanism of plasma actuation on controlling the detached shock wave was briefly analyzed.