双后掠乘波体的非线性升力增长

基于密切锥的双后掠乘波体是定平面形状乘波体的典型应用，除了具有良好的宽速域性能，其升力在高超声速大迎角下的非线性增长也是值得研究的现象。对比双后掠乘波体与单后掠乘波体的气动性能，发现双后掠外形比同等面积的单后掠外形具有更强的非线性增升效应，而且随着马赫数增加，其效应不断增强。分析乘波体不同部件的气动力，发现这种增升主要来自下表面，上表面贡献很小，指出相关学者提出的"涡升力"观点存在问题。本文研究表明，双后掠乘波体升力随迎角的非线性增加，与后掠角对激波附着的影响有关：后掠角越小，激波越难脱体，只要激波附着，参考斜激波关系式，波后的压力随迎角的增长就是非线性的，导致升力增长非线性；而激波脱体，升力增长则趋于线性。

Nonlinear lift increase of double swept waverider

The double swept waverider is a typical application of the planform-customized osculating-cone waverider. The satisfactory wide-velocity-range performance and the nonlinear increase of the lift for the double swept waverider at high angle of attack are well worth studying. The aerodynamic performance of the double swept waverider is calculated and compared with that of the single swept waveriders. Results suggest that the nonlinearity of the lift of the double swept waverider is stronger than that of the single swept waverider, and the nonlinearity effect increases as the Mach number increases. Since the main lift of the waverider comes from the lower surface rather than the upper surface, and the flow field above the upper surface in the hypersonic state is different from that in the subsonic state, the explanation to "vortex lift" remains questionable. This article proposes an alternative explanation that the nonlinear lift increase is related to the attachment of shock wave influenced by the sweep angle. The smaller the sweep angle is, the stronger the shock wave attaches to the waverider. In reference to the function of the oblique shock wave, the attachment ensures that the pressure increase via angle of attack is nonlinear, leading to the nonlinearity of the lift. When the shock wave detaches from the waverider, the increase of the lift brcomes approximately linear.