随着航空航天技术的发展，飞行器的飞行速度由最初的亚声速发展到超声速，最终发展到现在的临近空间高超声速飞行。临近空间高超声速远程机动滑翔飞行器的升阻比决定着其是否满足航程与横向机动能力的要求。乘波体在设计工况飞行时下表面产生的附体激波限制了高压气体从下表面向上表面泄露，从而可以获得很高的升阻比，这一优势使其在高超声速滑翔飞行器设计中有着广阔的应用前景。然而，在实际工程应用中，为了满足防热要求，乘波体前缘必须进行钝化处理，而前缘钝化会导致乘波体气动性能显著降低。因此，传统的尖前缘最优构型并不能保证钝化后仍为最优。针对这一问题，本文深入研究了前缘钝化效应对乘波体气动特性的影响机理，并提出了一种钝前缘乘波体优化设计方法，主要工作如下：
1）通过CFD数值模拟研究了不同程度的前缘钝化对乘波体气动特性的影响规律和作用机理。前缘钝化后，乘波体升力显著降低，阻力大幅增大，使得升阻比急剧降低；此外，纵向压心显著后移，改变了配平特性。前缘钝化影响可分解为钝前缘本身气动力影响和钝前缘产生的脱体激波对上、下表面的影响两部分。研究发现，钝前缘本身的波阻在总波阻增量中占主导作用，而其产生的升力较小；脱体激波对上、下表面的波阻影响较小，但会造成上、下表面升力大幅降低；由于钝前缘本身的摩阻增加量和脱体激波造成的上、下表面摩阻降低量近似抵消，因此钝化前后的乘波体总摩阻变化量很小。进一步分析表明，脱体激波造成的“压力过膨胀效应”导致了上、下表面升力和波阻的降低以及纵向压心的后移，而钝化后上、下表面边界层位移厚度的大幅增加使得其摩阻显著降低。
2）为了获得气动性能更优的钝前缘乘波构型，需要将前缘钝化效应影响直接引入乘波体优化过程中。针对现有气动力模型在捕捉钝化效应影响方面的不足，通过机器学习符号回归方法建立了一种能够快速评估脱体激波对乘波体上、下表面压力分布复杂影响的压力增量模型；以此为基础，结合切锥法、激波-膨胀波关系式、修正的牛顿理论、摩阻公式和有效外形半经验公式等方法，并基于钝化前后乘波体总摩阻不变的合理假设，提出了一种高效的钝前缘乘波体气动力计算方法。与不同工况、不同钝化半径以及不同乘波构型的CFD仿真结果对比表明，该方法具备较高的精度，克服了传统高超声速气动力模型无法准确捕捉钝前缘乘波体气动性能的缺点。
3）结合钝前缘乘波体气动力计算方法和遗传算法，构建了一种钝前缘乘波构型优化框架。基于该框架，可以优化得到满足前缘钝化半径约束、升力系数约束以及设计点配平约束的钝前缘最优乘波构型。优化结果表明：相比于尖前缘最优构型，钝前缘最优构型宽度更窄，其头部附近相同纵向位置处的后掠角更大，且升阻比显著提升。在M∞=15、H=50km设计条件下，当升力系数约束CL=0.4时，钝化半径R=10mm的钝前缘最优构型设计点升阻比相比前缘钝化10mm的尖前缘最优构型提升量可达12.0%。并且，随着升力系数约束增加、前缘钝化半径约束增加以及飞行高度降低，钝前缘最优构型的设计升阻比提升量逐渐增加。此外，当优化过程中引入纵向压心约束时，得到的钝前缘最优构型的升阻比和配平特性都显著提升。

Hypersonic vehicles are undergoing the development from the traditional ballistic re-entry flight to the long-endurance maneuvering flight in the near space. For the near space long-range maneuvering hypersonic glide vehicle, its lift-to-drag ratio determines whether it can meet the requirements of range and lateral maneuvering ability. During flight, the attached shock wave generated at the leading-edge of waverider limits the leakage of high-pressure gas from the lower surface to the upper surface, thus having a higher lift-to-drag ratio than the traditional configuration. The advantages of the high lift-to-drag ratio make it a promising application in the design of hypersonic glide vehicle. However, in practical engineering applications, in order to meet the requirements of heat protection, the leading-edge of the waverider need to be blunted, so that the aerodynamic performance of the waverider will be significantly reduced. Therefore, the optimum configuration based on the sharp leading-edge waverider cannot guarantee that it will be optimum after bluntness. This paper focuses on the influence of leading-edge bluntness on the aerodynamic characteristics of the waverider and the optimization design method of the blunted leading-edge waverider. The main work is as follows:
1) Aiming at the problem that the blunted leading edge will significantly affect the aerodynamic performance of the waverider, the influence trends of the bluntness effect on the total lift, total drag, lift-to-drag ratio and longitudinal pressure center of the waverider are studied. Then the influence of the bluntness is divided into the influence of the blunted leading-edge and the influence of the detached shock wave generated by the blunted leading-edge on the upper and lower surfaces and the reasons of the lift-to-drag variation caused by the bluntness are deeply analyzed, including lift, wave drag and friction drag. It is found that the lift of upper and lower surfaces decreases greatly, and then the total lift of the waverider decreases significantly. The wave drag of the blunted leading-edge plays a leading role in the total wave drag increment caused by bluntness, while the bluntness has little effect on the wave drag of the upper and lower surfaces. Since the friction increase of blunted leading edge and the friction decrease of upper and lower surfaces almost cancel each other, the total friction drag variation of the waverider caused by the bluntness is small. On this basis, the mechanism of waverider lift, wave drag and friction drag variation caused by blunted leading-edge is further studied. The results show that the pressure overexpansion effect caused by bluntness results in the decrease of the lift and wave drag of the upper and lower surfaces and the backward movement of the longitudinal pressure center, while the friction drag of the upper and lower surfaces is significantly reduced by the large increase of the boundary layer displacement thickness after bluntness.
2) In order to obtain better aerodynamic performance of the blunt leading edge waverider, the effect of blunted leading-edge on the aerodynamic performance of the waverider should be directly considered in the optimization process. Aiming at the shortcomings of existing engineering aerodynamic models in capturing the blunt effect, a mathematical model was established by symbolic regression to rapidly evaluate the complex influence of the detached shock on the pressure distribution on the upper and lower surfaces of the waverider. In addition, based on the assumption that the variation of total friction drag of the waverider caused by bluntness can be ignored, a high-efficiency and high-precision aerodynamic force calculation method for the waverider with blunted leading-edge is established by combining the model established by symbolic regression, the improved tangent-cone method, the shock-expansion wave theory and the modified Newton theory. This aerodynamic model overcomes the weakness that the traditional hypersonic aerodynamic model cannot capture the impact of blunted leading-edge on the aerodynamic performance of the waverider. Meanwhile, the CFD numerical method verifies that this method has high reliability in different flight conditions, different bluntness radii and different configurations.
3) In order to study the optimization design of blunted leading-edge waverider, an optimization framework of blunted leading-edge waverider was constructed by combining aerodynamic calculation method and genetic algorithm. Based on the optimization framework, the waverider with blunted leading-edge can be directly generated during the optimization process, which satisfies the constraints of the leading-edge bluntness radius, lift coefficient and trim. Compared with the traditional sharp leading-edge waverider optimization , the optimization of blunted leading-edge waverider can directly consider the influence of the blunted leading-edge in the optimization process, so it can obtain the blunted leading-edge waverider with better aerodynamic performance, and the optimum configuration with blunted leading-edge is closer to the engineering requirements.