To reveal the flow field characteristics of dual synthetic jets impinging plate, the large eddy simulation method was used to numerically study the flow of dual synthetic jets impinging plate. The Lagrangian coherent structure of the flow field was identified on the basis of the finite-time Lyapunov exponents, and the results were compared with the vorticity results in the Euler frame. It is found that the vortex structure of the jet core area of dual synthetic jets is exceeding complex and rich under the alternating action of periodical jets, and there is a pair of stable vortex structure far away from the core. Lagrangian coherent structures are well corresponding to the vorticity, provided guidance for the layout design of dual synthetic jets impingement cooling. Proper orthogonal decomposition analysis is performed on the flow field of dual synthetic jets. The results show that the first-order mode is approximately symmetrical about the central axis of the exit of the actuator, and its energy accounts for 35% of the total energy, and the first 6 modes account for 80%. According to the characteristics of the flow field reflected by the first 6 modes, the flow field of dual synthetic jets impinging plate has a high degree of symmetry.

To investigate the flow control characteristics of a dual synthetic jet in thrust vectoring, the peak velocity and excitation frequency of the dual synthetic jet were adjusted to reveal its control mechanisms over the nozzle mainstream deflection. The dynamic mode decomposition method was applied to extract and analyze the dominant flow field modes. Concurrently, an external flow of 34 m/s was applied to examine the mainstream deflection in the nozzle coupled with a flying wing structure. Results indicate that increasing the peak velocity of the dual synthetic jet expands the influence range of the low-pressure region in the flow field, leading to an increase in the mainstream deflection angle to 22°. Elevating the excitation frequency of the dual synthetic jet promotes the growth of the mainstream deflection angle, which tends to stabilize when the frequency exceeds 100 Hz. Regarding the flow control mechanism: during the suction cycle, the ventral orifice of the dual synthetic jet ingests the mainstream, forming a localized low-pressure region that induces mainstream deflection; during the blowing cycle, the mainstream recenters, causing the formation of wall-attached separation vortices on the downstream wall. The dorsal orifice exhibits a critical vortex entrainment and ejection effect that accelerates the passive secondary flow. Further dynamic mode decomposition analysis revealed dominant vorticity and velocity fluctuations occurring both at the location of the dual synthetic jet installation and on the downstream wall. This demonstrates that the dual synthetic jet, despite its minimal energy contribution, governs the modal characteristics of the flow field, while the downstream wall enhances the mainstream deflection. Simultaneously, simulation studies on the flying-wing-coupled nozzle revealed that the current configuration induces flow recirculation on the upper wall, which suppresses the nozzle's mainstream deflection, resulting in a maximum deflection angle of only 10°.

Strake wings at large angles of attack experience significant degradation in aerodynamic performance due to the leading-edge vortex breakdown phenomenon, the effective control of which, however, has yet to be thoroughly explored. This study proposes an innovative control method utilizing dual synthetic jets to delay the leading-edge vortex breakdown. The results indicate that the aerodynamic performance of a 76°/40° strake wing can be improved by installing dual synthetic jet actuators away from the sweep path of the leading-edge vortex. The proposed control method can delay the strake vortex breakdown and thereby increase the lift coefficient at a wide range of the angle of attack (α). For instance, the vortex breakdown was delayed by 8.4% of the chord length at α=40°; the lift coefficient was increased by 7.51% at α=35°. The reason for such a significant improvement in aerodynamic performance was the effective energy injection, achieved by an anti-phase operating manner of two jets that continuously pushed low-energy fluids to rotate in the same direction. This operation method enhanced the leading-edge vortex’s capability to withstand the adverse pressure gradient, lengthened the chordwise extent of high-speed flows, and expanded the area of the low-pressure zone on the leeward side, thereby increasing the vortex lifting force. The above results demonstrate the dual synthetic jets’s potential in the attitude control of slender wings.

To delay the vortex breakdown position of the slender delta wing, this study innovatively proposes the application of control near the Leading-Edge Vortex (LEV) core sweeping path, which is called Coupled Core Rotation Dual Synthetic Jets (CCR-DSJ) control. The results show that the vortex breakdown points at each angle of attack are moved backward after control, and the maximum delayed displacement is 32.4% of the root chord at 30°. Besides, there is a linear relationship between the breakdown position and the angle of attack after control, indicating that CCR-DSJ control has a significant effect on the pressure gradient of the vortex axis. Furthermore, the lift coefficient C_L is enhanced after control, with a maximum C_L increment of 0.078 at 27°, and an effective increment interval of [25°, 32°]. This interval is different from most previous studies, which is directly related to the position of the actuators. According to the lift change mechanism, the angles of attack are divided into three stages: Stage 1 (α = 15°–25°), Stage 2 (α = 25°–32°), and Stage 3 (α = 32°–40°). In conclusion, CCR-DSJ control can significantly change the pressure distribution, thereby offering promising prospects for the flight stage of the slender delta wing.

This paper proposes a longitudinal aerodynamic control strategy for flying-wing aircraft utilizing dual synthetic jets to compromise the stealth performance and aerodynamic maneuverability. The performance of this method for a small-swept-angle flying wing at large attack-of-angle (AOA) is examined by investigating the interaction between leading-edge dual synthetic jets and flow fields at different AOAs. Results show that an array of dual synthetic jets at the leading edge can effectively increase lift, reduce drag, and increase the lift-to-drag ratio at large angle of attack. The nonlinearly varying pitch moment indicates that the roll attitude control at high AOAs can be realized. Dual synthetic jets induce periodically evolving vortices at the leading edge, strengthening the momentum mixing across the wall-normal direction and enhancing the capability to resist reverse pressure gradient. Depending on AOA, dual synthetic jets have varied performance. At the AOAs of 8−10 degrees, they can completely suppress the leading-edge separation, while at the AOA of 10 degrees, a small separation area around the trailing edge leads to a slight decrease of lift. At the AOA of 12 degrees, the separation line moves to the middle section of the wing. At the AOA of 14−16 degrees, they can only effectively suppress the flow separation around the spanwise front of the separation zone, but they can still improve the lift efficiency by intensifying the energy in the separation zone. At the AOA of 18 degrees, the flow over the suction surface is almost completely separated. Nevertheless, the suction at the leading edge increases so that a relatively high lift-to-drag ratio remains. Compared with traditional synthetic jets, dual synthetic jets can significantly improve aerodynamic performance, manifesting their great potential.