上下反翼对双后掠乘波体低速特性的影响

相比于传统乘波体外形, 双后掠乘波体在保持高超声速良好性能的条件下能够提升乘波体低速气动性能, 但其仍存在低速稳定性不好等缺陷. 本文从密切锥乘波体理论提出给定前缘型线的乘波体设计方法, 通过给定三维前缘型线分别生成具有相同平面投影形状的上反和下反机翼双后掠乘波体. 使用CFD技术评估不同上下反程度外翼乘波体的低速性能, 分析升阻特性以及流场涡结构特点. 选取稳定性判据, 研究上下反翼对纵向和横侧向稳定性的影响. 结果表明, 机翼上下反对乘波体低速升阻特性影响较小; 不同外形均为纵向静不稳定的, 且俯仰力矩变化趋势比较类似, 机翼下反可使气动焦点位置后移, 提升纵向稳定性; 机翼上反有助于提升乘波体的横向静稳定性, 而下反则会下降; 机翼上反可以提升侧向稳定性, 且上反程度越大提升效果越明显; 同时机翼上反使乘波体的偏航动态稳定性有明显提升, 下反则会降低, 影响程度与机翼上下反程度呈正相关. 通过结果分析, 说明通过机翼上下反改善乘波体低速稳定性是可行的, 为乘波体在宽速域高超声速飞行器中的应用拓展了途径. 

EFFECT OF DIHEDRAL WING ON LOW SPEED PERFORMANCE OF DOUBLE SWEPT WAVERIDER

The double swept waverider has advantageous performances in subsonic characteristics and nonlinear vortex lift, while maintaining the high lift-to-drag ratio in hypersonic state, overcoming some deficiencies of the traditional waverider. However, it still has some defects such as poor low-speed stability. The waverider design given a 3D leading edge is developed from the osculating-cone treatment, and the double swept waveriders with wing dihedral and anhedral were generated by customizing the leading edge curves, which shared the same planform shape. Using CFD techniques, the low speed performances of the waveriders were evaluated, the lift drag characteristic and vortex structure were analyzed, and the effect of the wing with positive and negative dihedral angles, namely wing dihedral and wing anhedral, on stability was also studied. Results show that compared with the configuration whose projection in the front-view direction was a horizontal line, the configurations with wing dihedral and anhedral had nearly the identical lift-to-drag ratio. Different configurations were all unstable in longitudinal static stability, and the pitching moment of these configurations were similar. With wing anhedral, aerodynamic center moved backwards, increasing longitudinal stability; the wing dihedral improved the directional stability, while wing anhedral decreased it; wing dihedral improved the lateral stability, and the effect was stronger with higher wingtips. The dynamic directional stability of the waveriders can be improved by the wing dihedral obviously, while wing anhedral decreased it, and the effects was positive correlation to the distance of wingtips went up or down. According to the results, it was feasible to improve the low-speed stability of waverider by wing dihedral and anhedral, and the method provides a novel way to design the wide-velocity-range hypersonic vehicles.