The thrust vectoring technology is the key technology of high-performance aircraft, which can be divided into the mechanical and the fluidic thrust vectoring technology. The fluidic thrust vectoring technology has advantages of simple structure, fast deflection response and low energy consumption, so it has been widely studied. However the problems of jump and nonlinearity of the control law exist in the current rectangular fluidic thrust vectoring nozzles. Meanwhile the maximum deflection angle is small, which seriously limits the engineering application of this technology. A new type of the rectangular multi-wall passive thrust vectoring nozzle is developed in this paper. In order to figure out whether this new nozzle can realize the vector control of the jet with high linearity and larger deflection angle, two control strategies of the multi-section wall under multi-wall passive secondary flow and the variation of the initial passive secondary flow rate are employed. The characteristics of the dynamics and flow field of the jet are studied by means of experiment and numerical simulation. The results show that these control methods improve the linearity of the control law of the force vector angle, and the effective deflection force vector angle is increased. The linearity of the control law increases from 62% to 90.8%, and the maximum deflection force vector angle increases from 18° to 22°. When the initial inlet and outlet area ratio of the passive secondary flow is 1.16, the line-arity is further increased to 94.9%. It is found that there is no obvious separation bubble structure near the wall of the nozzle during jet deflection, which preliminarily explains the principle of the linear continuous control law of the nozzle.

To address the energy consumption issue in data centers, this study investigates the Single-Phase Immersion Liquid Cooling (SPILC) system by an experimental platform. The influential mechanisms of the coolant flow rate and chip power on the SPILC performance are analyzed. The results indicate that the heat transfer of chips located at inlet regions is more influenced by board layout than that of the chips at the outlet region. Moreover, the chip case temperature shows a trend of slight increase followed by a decrease as the flow rate increases. There exists a critical flow rate beyond which further increase does not significantly improve the SPILC performance. Additionally, the chip case temperature rises significantly with increasing power, and lower flow rates result in greater temperature increases. When the flow rate does not exceed 4.0 L/min, the chip power has almost no effect on the system pressure drop. Moreover, the influence of the flow rate on the power usage effectiveness of SPILC systems is significant when the total chip power is low, but this effect is greatly weakened as the chip power increases.

By designing an array integrated electrostatic atomization device with double-layer cross space shielding electrodes, using an optical visualization system and a high-speed spray particle size analyzer, the evolution characteristics of the jet morphology of the integrated electrostatic atomization of stable multiple jets were accurately recorded, and the voltage range of the integrated electrostatic atomization of stable multiple jets and the size distribution characteristics of spray droplets under different integration degrees and supply flow rates were discussed. The results show that the voltage range for stable atomization of multiple jets in the array integrated device is higher than that in the single capillary device, and the number of stable jet strands is weakly affected by the applied voltage. Under the same single capillary supply flow rate, the increase of the total supply flow rate due to the improvement of the integration degree has no obvious effect on the average droplet size, droplet size distribution range and cumulative volume distribution of the overall spray, but can cause the peak value of the volume distribution to decrease accordingly. At the same integration level, the average droplet size increases nonlinearly with the increase of the total supply flow, and the growth rate decreases with the increase of the total supply flow. The array integrated microchannel stabilized multi jet atomization system can significantly increase the supply flow while maintaining the particle size distribution of spray droplets in a narrow range, showing good monodispersity.

This paper is based on a circulating water tunnel, employing high-speed photography and pressure sensors to measure the flow characteristics of the ventilated cavity around a conical axisymmetric body. The focus of the discussion is on the flow characteristics of ventilated cavities at high Froude numbers and the pressure evolution on the axisymmetric body surface for different cavity shapes. The research results indicate that under high Froude numbers, gravity effects can be neglected, and ventilated cavities around the conical axisymmetric body exhibit three typical flow patterns: foamy cavity (FC), intermittent and transparent cavity (ITC), and continuous and transparent cavity (CTC). Among these, FC cavities are found within a small ventilation rate range, accompanied by some small-scale cavity shedding at cavity’s trailing. The transient pressure distribution on the axisymmetric body surface exhibits high-frequency, low-amplitude fluctuations, with the maximum pressure coefficient fluctuation amplitude of 0.18. ITC cavities represent a transitional flow pattern between FC and CTC, characterized by the shedding of large-scale cavity clusters from the cavity’s trailing, resulting in low-frequency, high-amplitude fluctuations in the transient pressure distribution on the axisymmetric body surface, with a maximum pressure coefficient fluctuation amplitude of 0.49. CTC cavities are observed within a large ventilation rate range, exhibiting similar characteristics in cavity shedding and pressure pulsation to ITC cavities. Under specific Froude numbers, during the transition from FC to CTC, the pressure on the axisymmetric body surface at different measurement points exhibits a trend of initially decreasing, then increasing, and finally stabilizing.

As a new type of micro aircraft configuration, the jellyfish-like flying aircraft has the advantages of low noise and flexible maneuvering, which has attracted the attention of the academic community. In this paper, a pair of two-dimensional plates rotating around fixed axes is used as a simplified model of jellyfish-like flapping wings. The disturbed flow fields in static water are measured by the time-resolved particle image velocimetry. By controlling the frequency and angular amplitude of the flapping motion, the influence of the motion parameters on the vortex characteristics and evolution law is studied. The vortex generation, shedding, and interaction processes are analyzed by using the phase average method and the circulation tracking technique. The forming mechanism of thrust is explained from the perspective of vortex dynamics. The experimental results provide certain references for the design of the jellyfish-like flying machines.

In recent years, relevant studies have shown that wing sections with humpback whale-like leading-edge protuberances can effectively delay stall and improve aerodynamic performance after stall. To investigate the flow separation phenomenon of the biomimetic leading-edge protuberances wing section, a particle image velocimetry (PIV) experimental study on the NACA 63₄-021 wing section and modified wing sections with single and double leading-edge protuberances is carried out. The distributions of statistics such as the average velocity of the wing section suction surface and the turbulent kinetic energy at different angles of attack are compared. The proper orthogonal decomposition (POD) method is adopted to analyze the experimental data. The flow structures during the stall process are analyzed from an energy perspective. The study finds that: both single and double leading-edge protuberances wing sections have two-step stall characteristics. When a unilateral stall occurs, there is a stable attached flow at the convex peak, which suppresses the extension of the stall zone to the other side of the convex peak and plays a role similar to a wing blade. Compared to the single leading-edge protuberance wing section, the wing section with double leading-edge protuberances undergoes stall mode transition at smaller angles of attack. The energy of each mode of POD decomposition is related to the stall mode at which the wing section is located. The characteristics of the flow structure in the flow field change with the switching of stall modes. The flow separation mode of the single leading-edge protuberance wing section exhibits instability during the transition from unilateral stall to bilateral stall. This study provides an experimental reference for the theoretical research and potential engineering application of biomimetic leading-edge protuberances wing sections.

The complex wave structures generated by a ship significantly influence the wave-making resistance, which is a critical factor in optimizing vessel performance and hull design. Traditional measurement methods, such as wave height gauges, are limited by sparse measurement points, low spatial resolution, and potential interference with the wave surface, making them unsuitable for full-field wave surface measurements in complex wave systems. To address these limitations, a non-contact measurement method for ship wave surfaces based on multi-view stereoscopic vision is presented. The proposed scheme includes: applying neural networks for spatial calibration and the three-dimensional reconstruction of feature points, using an ant colony optimization particle tracking algorithm for perspective matching, and conducting principal component analysis for still water baseline correction. Experimental results demonstrate that the proposed method can realize the wide-area free-surface measurement of the ship wave and effectively capture typical wave characteristics at various ship speeds. Compared to traditional measurement, the stereoscopic vision approach offers enhanced flexibility and suitability for real-time measurement of dynamic wave fields over large areas.

In liquid environments, nanoscopic soft materials typically adopt a cap-like shape to maintain their stability. Therefore, their morphology characterization and identification remain challenging in the liquid phase. The present study employs Atomic Force Microscopy (AFM) to achieve high-resolution imaging of subaqueous micro-nano blisters, polymer droplets, and surface bubbles. By analyzing the morphological changes in various scanning forces, the morphological characteristics of these nanoscopic soft materials are investigated. Subsequently, nanoindentation tests are conducted to analyze the interaction between the probe and the solid-liquid-gas interfaces, and their mechanical properties are obtained. The results show that under a scanning force of 0.50 nN, all blisters, droplets, and bubbles exhibited cap-like shapes. Under a higher scanning force (5.0 nN), the blister morphology remained constant, the droplet volume decreased, and the bubble disappeared. Force-distance curves at the vertex under a load of 3.0 nN indicate that all the three experienced elastic deformation. The probe has to overcome greater adhesion force to detach the droplet, while bubbles display a two-stage elastic deformation. Furthermore, due to the influence of anchoring effects, the considered objects exhibit stronger resistance to deformation near the edge of the spherical cap. The modulus of the polymethyl methacrylate (PMMA) nanofilm is independent of the applied load during elastic deformation caused by blister and it is estimated to be around 3.38 GPa. The interfacial tension of small-sized PDMS droplets underwater is approximately 37.3 mN/m, while the gas-liquid interfacial tension of surface bubbles is approximately 32.5 mN/m.

Rotating structures are commonly used in the transportation and energy generation fields. As a non-contact optical measurement technique, the Three-Dimensional Digital Image Correlation (3D–DIC) allows for the full-field spatial measurement of displacement, deformation and vibration of rotating objects in operation, which provides important data support for damage detection, health monitoring and aerodynamics structural optimization design. A review of the extensive studies on the development and application of 3D–DIC is presented. First, the principle of 3D–DIC and its rotating object measurement setup are introduced. Particularly, in cases when the deformation involves a large rotation, a de-correlation problem emerges. To address this, many scholars have proposed initial value estimation and shape function design methods for large-rotation objects, which are investigated extensively here. Several application cases utilizing 3D–DIC for damage detection and vibration measurements are introduced, showing its unique advantages compared with traditional deformation measurements methods. Lastly, the applica-tion prospect and development trend of this technology are prospected.

Icing in the form of impinging supercooled droplets accounts for the most cases of aircraft icing. This review provides an in-depth discussion over single sessile droplet icing, impinging of a droplet, and the combined icing of an impinging droplet. Special focus is placed on icing of an impinging supercooled large droplet, which is of significant importance in the study of aircraft icing. The effects of a few key parameters, such as the impinging speed and droplet size, are studied and analyzed. Meanwhile, by studying the factors influencing the dynamics of droplet impact icing, the icing phenomena of room temperature droplets and supercooled droplets are investigated, and it turns out that the initial thermophysical properties, heat transfer mechanisms and phase transition modes vary drastically, and the kinetic behaviors such as nucleation time, ice crystal type, interfacial heat transfer characteristics and phase advancing velocity as well as the droplet morphology are significantly different. The effects of the impact velocity, particle size and surface wetting on droplet impact icing are indicated, providing a theoretical basis and reference for the design and development of anti-deicing technology for aircraft.