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 address the heat dissipation challenge in aerospace and electronics, this paper undertakes liquid cooling experiments utilizing a novel multi-orifice dual synthetic jets actuator (MODSJA). The performance of the DSJ-based liquid cooling device and the associated flow fields are thoroughly analyzed, considering the effects of various parameters, including heat flux, channel inlet flow rate, and driving frequency. Results indicate that the wall temperature of the device increases with increasing heat flux. When DSJ is on, the wall temperature decreases; otherwise, the wall temperature reduction can also be achieved by increasing the inlet flow rate, which substantially increases the pressure drops. This is because higher flow rate allows the fluid to carry away faster heat more quickly, resulting in a temperature drop. When the actuator is activated at a flow rate of 0.16×10^–3 m³/min, the wall temperature is reduced by 3.07 ℃, which is comparable to that achieved with an inlet flow rate of 0.4×10^–3 m³/min when the actuator is off. This indicates that the pump power requirement can be reduced at least 583.08% without causing additional pressurerop. Within the frequency range under investigation, the DSJ liquid cooling device achieves an optimal performance at 20 Hz, yielding a wall temperature decrease of 3.80 ℃ and a marginal increase of 0.03 kPa in the pressure drop. Moreover, a higher driving voltage results in a more pronounced wall temperature drop, achieving a maximum reduction of 4.16 ℃ at 240 V. In summary, the experimental results clearly show that DSJ can achieve significant heat dissipation with a negligible increase in pressure drop, thus making it a promising solution for heat management in aerospace and electronic applications.

Icing poses significant hazards to aviation safety. Superhydrophobic surfaces have gained widespread attention for their capability to induce rebounding and detachment of impacting water droplets from surfaces, thereby achieving anti-icing. When icing occurs on equipment such as wind turbines and aircraft, the droplet diameter typically ranges from micrometers to tens of micrometers, and the surface is often in motion. However, experimental research on the characteristics of micrometer-scale water droplets impacting moving superhydrophobic surfaces remains vacant. Consequently, in this paper, we developed an experimental platform to investigate the impact of micron-sized water droplets on moving superhydrophobic surfaces. High-speed photography revealed that, contrary to observations with millimeter-scale droplets, the contact time of micrometer-scale water droplets impacting superhydrophobic surfaces increases significantly (by 78%) at high surface tangential velocities. Furthermore, numerical simulations were conducted to gain deeper insights into the impact process, particularly focusing on the influence of surface motion on the impact characteristics of water droplets. This influence mainly manifests in three aspects: it prolongs the centroid descent process, redirects water droplets from the expansion direction to the flow direction, and changes the expansion and retraction characteristics of water droplets. The extension of the contact time of micrometer-scale water droplets due to the high-speed motion of superhydrophobic surfaces is attributed to the intense stretching of the water droplets' front edge. Subsequently, by applying dual synthetic jets to water droplets, the tangential relative impact velocity between the droplets and the surface is decreased, resulting in a 28% reduction in the contact time. This research deepens the understanding of the impact dynamics of micron-sized droplets on moving walls and provides new insights for developing active and efficient anti-icing/de-icing technologies based on superhydrophobic surfaces.

To further advance the development of Dual Synthetic Jet (DSJ) based anti-icing/de-icing technology, we established an experimental setup to control the trajectory characteristics of droplets using DSJ. The effects of the actuator driving voltageand driving signal phase on the droplet trajectory were studied using high-speed photography under the conditions of the actuator being stationary relative to the dropletand existence of relative motion. The horizontal velocity of the droplet 375 μs after being affected by the jet was used as an index to assess the impact of the jet on the trajectory characteristics of the droplet. When no relative motion existed between the actuatorand the droplet (the turntable being stationary), the speed increased linearly from 0.65 m/s at a driving signal amplitude of 60 V to 2.29 m/s at 165 V. The phase of the jet at the time of droplet generation had a significant impact on the trajectory of the droplet. With a driving signal amplitude of 165 V, the speed varied from 1.11 m/s to 4.98 m/s at different initial phases of the jet. When the actuator approached the droplet at a linear speed of 4.4 m/s (achieved by rotating the turntable), the speed increased from 1.57 m/s at a driving signal amplitude of 60 V to 3.25 m/s at 165 V. Moreover, the rotation of the turntable itself had little effect on the speed. Additionally, when the turntable was rotating, the change in the speed with the initial phase of the jet had a time lag compared to when the turntable was stationary, but the overall trend was similar, and the corresponding the speed was larger when the turntable was rotating. The results indicate that the jet could rapidly increase the velocity of the droplet to a level close to that of the jet in the area where the droplet was generated. Even when the turntable rotated at higher speeds (with a maximum relative linear velocity of 22.0 m/s between the actuatorand the droplet in the experiment), the dual synthetic jet still significantly affected the trajectory of the droplet.

Superhydrophobic surfaces, which can promote the rebound of impacting water droplets, have become a research hotspot in the field of anti-/de-freezing. However, under practical freezing conditions, the performance of superhydrophobic surfaces may deteriorate during droplet impact, leading to anti-freezing failure. We employ an active control technology using dual synthetic jets to suppress freezing. A low-temperature experimental system was built, and high-speed photography along with numerical simulations were used to analyze the freezing characteristics of water droplets impacting superhydrophobic surfaces at −30 ℃ and the control effect of dual synthetic jets. The results show that, without using dual synthetic jets, droplets ultimately adhere to the surface and freeze; with the application of dual synthetic jets, droplet separation from the ice layer is effectively promoted, significantly reducing residual ice on the surface. Numerical simulations further reveal that dual synthetic jets inhibit ice formation by enhancing droplet motion, altering local heat transfer, and modifying the flow field structure, providing a valuable reference for the development of novel low-energy consumption anti-/de-freezing technologies.

The complex flow characteristics of transverse jet in high-speed crossflow involve several separation regions and multiple shock waves, which make it difficult to capture and precisely predict the flow field state in real time merely by relying on traditional approaches. With the rapid advancement of deep learning technology, its powerful data processing capability offers a fast method for the prediction of the transverse jet flow field. Consequently, a prediction model based on deep learning is established, with the aim of obtaining the flow characteristics of a transverse jet under different freestream and jet conditions. This study segments the complex grid into several individual grids and trains them independently. The trained model can successfully establish the nonlinear mapping relationship between the transverse jet flow field and the input parameters. The prediction accuracy of the established model for the wall pressure under different conditions exceeds 99%, and the established model is also capable of reproducing structures such as shock waves and recirculation zones in the overall flow field, thereby achieving highly precise and efficient prediction of the jet structure and flow information. The results suggest that in contrast to the traditional numerical simulation, this deep learning model demonstrates greater efficiency in predicting the transverse jet flow field.

Active flow control technology is a frontier and transformative technology in the aviation field of the 21st century. Dual Synthetic Jet (DSJ), a new type of active flow control technology invented in China offering high energy efficiency, strong environmental adaptability, and wide control range, is expected to fully assist in the performance improvement of current aircraft and the revolutionary development of next-generation aircraft. This paper systematically summarizes the theory, technical characteristics, and the latest research progress of DSJ in empowering aviation technology. Through twenty-year research, the DSJ theory system based on the “enhancement” effect, “vector” effect, and “augmentation/self-support” effect existing between double synthetic jets with different phases has been formed. And the DSJ technology system with characteristics of energy efficiency doubling, full electric vectoring, and cross-medium working ability has been developed. DSJ has shown great application prospects in aspects of aircraft aerodynamics, power, flight control, flight safety, thermal control and cross-medium flight.

This study investigates the flow separation control capability of an array of dual synthetic jets on a high-angle simple flap. Through numerical simulations. The aerodynamic control characteristics and mechanisms of the flow field around the airfoil were analyzed under various parameters, with a detailed examination of the control evolution of the separation vortex. The results indicate that as the dimensionless momentum coefficient C_μ increases, the control effectiveness of the dual synthetic jets for flow separation progressively improves. Optimal lift enhancement and drag reduction effects are achieved when the dimensionless driving frequency F⁺=3.088 and the momentum coefficient C_μ=0.028 99, resulting in the best overall control performance within the investigated cases. Additionally, the array of dual synthetic jets effectively controlled the evolution of the separation vortex on the high-angle simple flap by accelerating the airflow over the upper surface of the airfoil attracting high-speed airflow from the shear layer to reattach to the surface, and low-energy airflow drawing in from the shear layer to counteract the viscous dissipation in the separation region. This cyclic process transforms the development of large-scale spiral vortices into smaller-scale vortices, alleviating the adverse pressure gradient on the flap surface and reducing energy dissipation in the flap.

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.

Active flow control has a wide range of applications in supersonic/hypersonic missiles, in which transverse jets have demonstrated an excellent performance in the fast response to flow. To address the problem of transverse jets in hypersonic missiles, this study carries out numerical simulations on the effects of the jet array and jet temperature on the flow structures. Firstly, the typical flow structures of a transverse jet are analyzed. The strong interaction between the under-expansion jet and the incoming flow forms a horseshoe recirculation zone in front of the jet, and the fluid passing through the barrel shock and the Mach disk together with the incoming flow forms a counter-rotating vortex pair that can interfere with the downstream shock. As the jet temperature increases, the area of the high-pressure zone increases, and the counter-rotating vortex pair induced by the jet causes stronger interference to the downstream shock, resulting in an enhancement effect on the pitching moment. An array of jets can obviously enhance the pitching moment, but when the jet temperature is high, the bow shock in front of the transverse jet will converge towards the lower surface along the circumference of the missile from both sides. This phenomenon makes the enhancement of the pitching moment weakened, therefore a reasonable jet spacing and temperature should be selected when arranging an array of transverse jets.