单膨胀斜面喷管在过膨胀状态时气流发生分离，推力显著下降并产生明显的低头力矩，是吸气式高超声速飞行器难以跨声速飞行的主要原因之一。针对此问题，本项目提出开展基于无源腔的单膨胀斜面喷管流动控制方法研究，通过三维数值模拟深入分析带无源腔的单膨胀斜面喷管流场细节，利用典型工况实验验证准确反映喷管和无源腔流动形态的计算模型，分析不同落压比条件下无源腔的孔径、孔深、孔型、开孔率和开孔范围对单膨胀斜面喷管的流动分离区域、推力性能和矢量角影响的关联关系。通过研究，能掌握单膨胀斜面喷管中无源腔结构抑制和增强流动分离的机理，明确无源腔法在单膨胀斜面喷管中的适用落压比范围，建立无源腔结构最优设计准则，为该法在单膨胀斜面喷管上的应用奠定基础。同机械法和主动流动控制法相比，无源腔法结构简单、重量轻且工作可靠、将是单膨胀斜面喷管的重要技术组成，本研究将为吸气式高超声速推进系统的喷管设计乃至高超声速飞行技术提供支撑。

The flow separation of the single expansion ramp nozzle(SERN) under serious over-expasion ratio condition, which causes marked deterioration of performance and undesirable pitch moment, is a crital technical bottle-neck to achieve aerocraft transonic flight. To settle the issue, the program will carry out the research on flow separation control mechanism of SERN based on passive cavity. Compared with traditional mechanical control and active flow control, passive cavity control method shows its advantage on lowing the complexity and weight of SERN by eliminating mechanical control components and secondary flow tubes. Based on theoretical analysis, numerical simulation and experimental measurements, the in-depth understanding of the flow mechanism of enhanced separation and alleviated separation inside and outside the nozzle with the passive cavity will be obtained, and an acceptable passive cavity caculation model will be investigated. the relationships between characteristic parameters (including flow separation zone of SERN, thrust performance and vector angle) and the affecting parameters including aerodynamic and geometric parameters will be clarified to determine the cavity design parameters which optimize the performance of the nozzle in the wide flight envelope. The research will provide the sound scientific basis for the integration design of the airbreathing hypersonic propulsion system.