A novel fluidic thrust-vectoring (FTV) control method based on dual synthetic jets actuator (DSJA) is proposed and evaluated. Numerical simulations are governed by the compressible Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations. According to the results, DSJA is capable of deflecting a primary jet with a velocity of 100 m/s and a height of 50 mm by approximately 18 degrees with a momentum coefficient of 1.96%. It produces comparatively linear control characteristics in almost all deflection angles evaluated (0~23 degrees). The low pressure generated by DSJA, the ejecting enhanced by DSJA, and the co-flow effect produced by the accelerated secondary jet all play roles in the deflection of the primary jet. Since the primary jet is strong enough, the potential of DSJA to provide thrust vector control is revealed.

High maneuverability is required for high-speed aircraft. However, the traditional control method with mechanical rudder surface deflection has some defects such as weak control ability and long response time. In this paper, numerical simulations analyze the ability of high-energy jet to improve the control efficiency of X-51A aircraft. The deflection angle of the rudder is 0°–18°, and the high-energy jet is applied to the head of the aircraft and the windward side of the rudder surface. The control effects of the two control methods are compared and analyzed. The results show that within the range of the rudder deflection angle mentioned in this paper, applying high-energy jet control on the head of the aircraft will weaken the rudder surface control efficiency of the X-51A-like aircraft, while applying high-energy jet control on the wind-side of the rudder surface can enhance the rudder surface control efficiency of the aircraft by 13.78%. In this study, numerical simulations were used to analyze the effect of applying high-energy jets at different positions to enhance the efficiency of the rudder surface of a high-speed aircraft. This paper offers a novel concept for employing active flow control methods to enhance the efficiency of high-speed aircraft's rudder surfaces, thereby improving the application potential of such aircraft. These findings can serve as a reference for future research on the efficiency of rudder surfaces in high-speed aircraft.

To effectively reduce shock wave loss at the trailing edge of a supersonic cascade under high back-pressure, a shock wave control method based on air jets is proposed. The air jet was arranged on the pressure side of the blade in the upstream of the trailing-edge shock. The flow control mechanism and effects of parameters were analyzed by computational methods. The results show that the air jet formed an oblique shock wave in the cascade passage which decelerated and pressurized the airflow. The resulting expansion wave downstream of the jet slot weakened the strength of the trailing-edge shock. This could effectively change the normal shock into oblique shock and thus weaken the shock loss. Optimal control effect was achieved when the mass flow rate ratio of the jet to the passage airflow remained 0.35–1.11% and the distance from the jet slot to the shock foot of the trailing-edge shock was about five times the thickness of the boundary layer. The proposed method can reduce the total pressure loss of a supersonic cascade, with the maximum improvement effect reaching 7.29% compared to the no-control state.

Transition delaying is of great importance for the drag and heat flux reduction of hypersonic flight vehicles. The first mode within low frequency and the second mode within high frequency exist simultaneously during the transition of hypersonic boundary layer. This paper proposes a novel bi-frequency synthetic jet to suppress low- and high-frequency disturbances at the same time. Orthogonal table and variance analysis are used to compare the control effects of jet with different frequencies, amplitudes and positions. Linear stability analysis results show that, low frequency synthetic jet can suppress the first mode when it is arranged upstream of synchronization point, while the second mode control effect is relatively weak. The higher the high frequency is, the stronger the suppression effect is on the first mode. For the second mode, the suppression effect is only at f2=89.09kHz. The larger the amplitude, the weaker the promoting effect for the first mode and the second mode, and the more obvious the suppressing effect. For the cases with synthetic jet downstream of synchronization point, all levels of the three parameters promote the unstable mode. In terms of the growth rate with the spanwise wave number, the control effect of the same factor and level under different spanwise wave number is different. In order to obtain the optimal control effect on transition, the three factors and the arrangement position of the synthetic jet should be selected as follows: the position is arranged in the upstream, with f1 = 17.82kHz, f2 = 89.9kHz, a =0.007, so that the maximum growth rate of the first mode is reduced by 9.06% and that of the second mode is reduced by 1.28% compared with the uncontrolled state.

Crossflow interaction constitutes a fundamental research topic in flow control, with extensive prior investigations on jet-crossflow evolution mechanisms. To explore the influence of underwater dual synthetic jets (UDSJs) on crossflow fields, a miniaturized actuator was employed for static flow analysis via particle image velocimetry experiments. The optimal frequency increased fivefold (from 34 to 170 Hz) compared to conventional designs, broadening the operational frequency range and establishing technical foundations for hydrodynamic control. Frequency- and momentum-dependent flow modulation was analyzed under incoming flow conditions by simulation. Transverse jet vortex structures comprise first vortex rings (FVRs), horseshoe vortices (HSVs), hairpin vortices (HVs), and counter-rotating vortex pairs (CVPs). High-frequency UDSJs generate complex structures including HSVs and HVs with extended CVP development and wider influence, while low-frequency jets exhibit enhanced penetration capability through full development of FVRs, maintaining greater CVP–wall distances. Higher momentum coefficients correlate with larger vortex structures, intensified strength, extended streamwise growth, reduced CVP spacing, and stronger entrainment. Results of dynamic mode decomposition reveal reduced inflow suppression and enhanced penetration at low frequencies and high-momentum coefficients, whereas high-frequency jets exhibit stronger vortex interactions and flow disturbances.

Transition delaying is of great importance for the drag and heat flux reduction of hypersonic flight vehicles. The first mode, with low frequency, and the second mode, with high frequency, exist simultaneously during the transition through the hypersonic boundary layer. This paper proposes a novel bi-frequency synthetic jet to suppress low- and high-frequency disturbances at the same time. Orthogonal table and variance analyses were used to compare the control effects of jets with different positions (USJ or DSJ), low frequencies (f₁), high frequencies (f₂), and amplitudes (a). Linear stability analysis results show that, in terms of the growth rate varying with the frequency of disturbance, an upstream synthetic jet (USJ) with a specific frequency and amplitude can hinder the growth of both the first and second modes, thereby delaying the transition. On the other hand, a downstream synthetic jet (DSJ), regardless of other parameters, increases flow instability and accelerates the transition, with higher frequencies and amplitudes resulting in greater growth rates for both modes. Low frequencies had a significant effect on the first mode, but a weak effect on the second mode, whereas high frequencies demonstrated a favorable impact on both the first and second modes. In terms of the growth rate varying with the spanwise wave number, the control rule of the same parameter under different spanwise wave numbers was different, resulting in a complex pattern. In order to obtain the optimal delay effect upon transition and improve the stability of the flow, the parameters of the bi-synthetic jet should be selected as follows: position it upstream, with f₁ = 3.56 kHz, f₂ = 89.9 kHz, a = 0.009, so that the maximum growth rate of the first mode is reduced by 9.06% and that of the second mode is reduced by 1.28% compared with the uncontrolled state, where flow field analysis revealed a weakening of the twin lattice structure of pressure pulsation.