In this Letter, hypersonic boundary-layer transition was investigated on a large-scale cone with a height of 3 m and a half-cone angle of 7° at a zero angle of attack in the JF-12 hypersonic flight duplicate shock tunnel. For the same freestream unit Reynolds number, with the increase in the bluntness Reynolds number, the transition Reynolds number has a trend of first increasing and then decreasing, showing a “transition reversal” phenomenon. As the bluntness increased, the high/low-frequency instability waves in the boundary-layer were modulated, which caused the boundary-layer transition to be delayed and then advanced.

In this research, to study the hypersonic boundary-layer transition, experiments were conducted on a large-scale flat plate with a length of 3.2 m at a zero angle of attack in the hypersonic shock tunnel duplicating flight conditions. Surface-mounted piezoelectric pressure sensors and coaxial thermocouples were, respectively, used to measure the pressure fluctuations and wall heat transfer. The spatial distribution of heat transfer was used to distinguish the transition. Under the test conditions of Ma = 7.0, T₀ = 2120 K, and Re_∞ = 6.08 × 10⁵m⁻¹, no transition occurred, and under the test conditions of Ma = 7.0, T₀ = 2220 K, and Re_∞ = 1.23 × 10⁶m⁻¹, the transition position was s = 2.06 m. The repeatability of the experiment was found to be good. Furthermore, focus was placed on the spectral and spatial/temporal evolution characteristics of pressure fluctuations in the laminar boundary layer. The experiment captured the three frequency distributions of mode waves in the laminar flow zone. Among the mode waves distributed in the three frequency bands, the low-/high-frequency bands were dominant, and the mid-frequency band exhibited a staged contribution. The amplitude energy percentages of the high- and low-frequency mode waves exhibited opposite trends in both time and space, which means that the disturbance energy will be distributed among the various harmonics in the laminar stage.

In this paper, Navier-Stokes equations were solved with high-order accurate schemes to investigate the basic structure and regularity of the flow field during the interaction of a supersonic jet and a codirectional supersonic incoming flow. A double backward-facing step model was proposed to investigate the interaction between the jet/supersonic incoming flow shear layers. The two shear layers interact to produce a secondary jet. The secondary jet produced by the action has a unique periodicity that is related to the overall oscillation of the shear layer. The secondary jet is generated when the horizontal angle of the jet shear layer reaches a certain value. This paper focused on the analysis and discussion of the periodicity of the secondary jet. When the aspect ratio is different, the period of the secondary jet changes significantly. However, when the static pressure ratio is different, the period of the secondary jet does not change much.

In this Letter, the dynamic effect of rotation on unsteady shock interaction between an oblique shock wave and bow shock ahead of an elliptic cylinder is numerically investigated. First, a non-deforming grid method based on a non-inertial reference frame is applied for supersonic/hypersonic flow around an arbitrarily moving body. A simulation considering a rotating elliptic cylinder is then conducted at Ma5 with forced-oscillation approach. The results show that the shock interaction structure during rotation has obvious hysteresis compared with the static condition, and transition among different types of shock interaction is also affected by rotation direction and speed. The mechanisms are briefly addressed.

Air-blowing is one of the techniques for active flow control and thermal protection system of hypersonic vehicles. Introducing air into the hypersonic boundary layer alters the cross-sectional profile of the boundary layer, thereby influencing the boundary-layer transition. This study investigates the active air-blowing control effects on the hypersonic flat-plate boundary layer under various blowing mass flow rates and incoming Mach numbers by solving the Reynolds-averaged Navier–Stokes equations with the Langtry–Menter four-equation transitional shear stress transport model. The study examined alterations in the blowing boundary-layer profiles under two conditions: natural and bypass transition, induced by different blowing flow rates. Blowing significantly alters the sonic line and boundary-layer profile characteristics, triggering blowing oblique shock and causing alterations in the instability mechanisms of the two transition states. A higher Mach number intensifies compressibility effects, stabilizing the boundary layer and leading to an increase in the thickness of the blowing boundary layer and air film.

The interactions between oblique and bow shock waves are significant problems related to the aerodynamic force and thermal performance of hypersonic vehicles, but few studies have considered the dynamic effect of the body's motion on the phenomena. In this work, a numerical study on the oblique and bow shock waves ahead of an elliptic cylinder rotating with a forced-oscillation approach was conducted at Mach 5 by solving the unsteady, two-dimensional Navier–Stokes equations in a non-inertial coordinate system. The hysteresis loops of aerodynamic coefficients were analyzed first, and it was found that the moment is sensitive to rotation. Then, two different hysteresis forms were found at positive and negative angles of rotation (AOR), corresponding to cases with the interference point above or below the wall, respectively. When AOR is positive, the rate-dependent transition hysteresis among various shock interaction types causes the movement of strong flow structures (reflected shock wave, Mach stem, and jet) to always lag behind the body's motion. When AOR is negative, besides the evolution hysteresis of flow structures, two unusual patterns between Edney Types III and VI were observed on different transition paths, which led to very different peak pressures. Also discussed are the driving mechanisms associated with the effect of the subsonic region and the downstream boundary of the interaction zone, as well as the modulating action of the formed virtual Laval flow channel. Additional simulations were performed to study the effect of rotation speed on the transition boundary and the transition structures between Types III and VI.