Near-space long-endurance unmanned aerial vehicles (UAVs) play an important role in persistent reconnaissance, communication relay, wide-area early warning, and emergency response missions. However, due to the extremely low atmospheric density and the cross-altitude flight characteristics of near-space operations, these vehicles encounter prominent low-Reynolds-number effects, reduced propulsion efficiency, and strong coupling between flight and propulsion systems. These challenges underscore the need for integrated flight-propulsion aerodynamic design. This paper reviews recent technical progress in this field for near-space long-endurance UAVs. Based on the configuration characteristics of near-space vehicles, three categories are identified: conventional-layout high-altitude long-endurance UAVs, low-dynamic large-flexibility high-altitude long-endurance vehicles, and stealth-layout high-altitude long-endurance UAVs. For each category, the primary technical challenges and the corresponding focuses of integrated flight-propulsion design are clarified. The theoretical framework of integrated flight-propulsion aerodynamics is then introduced, structured around a systematic research paradigm of modeling-constraints-tasks-evaluation. Following this, the application of robust optimization methods within integrated design is discussed. Specifically, conventional-layout platforms benefit from general integrated robust optimization; low-dynamic platforms require robust design that addresses distributed propulsion and airframe integration; and stealth-layout platforms place emphasis on robust intake and exhaust system design. Building on this foundation, the potential of passive flow-control approaches, such as variable-pitch passive control and bump control, and active flow-control techniques, such as synthetic dual-jet actuation, for enhancing aerodynamic and propulsion performance is further examined, and the distinct research focuses associated with the three platform types are summarized. Finally, the study synthesizes the research paradigm (modeling-constraints-tasks-evaluation) and key technical priorities for integrated flight-propulsion design in near-space long-endurance UAVs, and outlines future development directions involving robust integrated optimization and flow-control enhancement technologies.

Climate change has prompted the aviation industry to reduce greenhouse gas emissions. Variable-camber leading edges, with their adaptable aerodynamic shapes, hold significant potential for laminar flow wings and contribute to greener aviation. In response to this need, this paper proposes a design optimization method for a variable-camber leading edge featuring an outer variable-thickness composite compliant skin and an inner open-kinematic-chain mechanism. The optimization methodology employs a fiber continuity model based on a ply-drop sequence, a guiding sequence and a thickness sequence to describe the variable-thickness composite compliant skin structure, enabling direct generation of a composite layup sequence that meets fiber continuity criteria. Additionally, the design methodology for the inner open kinematic chain considers the rigid-flexible coupling effect and analyzes the number of driving ribs along the span-wise direction. Finally, a full-scale physical prototype for a large-scale civil aircraft is developed and experimented in the FL-10 wind tunnel, demonstrating that the variable-camber leading edge can smoothly and precisely achieve its target shape and hold its final profile under the corresponding aerodynamic loads, thereby validating the proposed design methodology.

The low dynamic near-space vehicle, such as high-altitude solar-powered Unmanned Aerial Vehicle (UAV) and stratospheric airship, has the potential for sustained flight. It has important application values in military and civilian areas, such as continuous wide area early warning and reconnaissance, monitoring and observation, emergency response, and disaster relief. At present, due to the constraints of high-altitude rarefied atmosphere conditions and the energy consumption demand of variable altitude overnight, the low dynamic near-space vehicle faces to the problem of insufficient multi-point working efficiency of low Reynolds propellers. In recent years, with the reduction of energy consumption and improvement of reliability of control components, the potential of application of flow control in improving propeller efficiency has become prominent. This paper summarizes the research progress of flow control technologies for propellers of low dynamic near-space vehicles. Firstly, the aerodynamic analysis technology of low Reynolds propellers for near-space low dynamic vehicles is reviewed. The aerodynamic analysis basis required for propeller flow control is defined. Secondly, based on the principles of variable pitch and active/passive flow control, the research status of propeller passive control is analyzed, such as trailing edge deformation control and blade tip winglet control. Thirdly, the progress of plasma jet flow control of propeller is introduced. The research status and limitations of co-flow jet flow control are described, and then the current situation and potential of dual synthetic jet flow control are analyzed. Finally, the scientific problems of flow control for the low Reynolds propeller are summarized, and the feasible research directions are put forward.