展向自适应机翼总体气动特性分析

Computational Investigation of Overall Aerodynamic Characteristics for Spanwise Adaptive Wing

针对展向自适应机翼的气动特性随折叠角度变化的问题,以经典翼型NACA0012为基础,设计了内外段比例为7∶1的展向自适应机翼。基于结构化网格和雷诺平均N-S方程,采用自主开发的流场求解器,研究了自适应机翼在不同速域、不同折叠角度情况下的总体气动性能以及操纵特性。从升阻比和机翼表面压力分布两个方面,对比了外段机翼在不同折叠角度下的总体气动效率以及折叠角度对流场特性的影响规律。研究结果表明,自适应机翼的对称变形在合适的折叠角度下可以使亚声速和超声速飞行条件下的气动效率大幅增加,增幅高达28%;亚声速飞行时的高气动效率来源于升力增加和阻力减小的共同作用,而超声速时的高气动效率主要来源于阻力的减小;在跨声速飞行条件下的气动特性随折叠角度变化不明显;非对称变形可以产生明显的用于方向操纵的滚转力矩和偏航力矩。通过将外段机翼折叠到不同角度,展向自适应机翼可以适应不同的飞行工况,获得更好的气动效益,可应用于下一代亚声速或超声速飞机。

To determine the effect of folding angle on aerodynamic characteristics of spanwise adaptive wing,configuration with a 7∶1 ratio between internal and external segments based on classical airfoil NACA0012 was designed.According to the structured grid and Reynolds averaged Navier-Stokes equations,the codes developed by ourselves were employed to investigate the overall aerodynamic performance and maneuverability in various speed domains and at different folding angles.The overall aerodynamic efficiency and folding angle effect on flow field characteristics at different folding angles of external wing were compared in terms of the lift-to-drag ratio and the wing surface pressure distribution.It is found that the symmetric folding of the spanwise adaptive wing can increase the aerodynamic efficiency significantly at appropriate folding angle in subsonic and supersonic flight regimes by up to 28%;the high aerodynamic efficiency in subsonic flight results from the combination of lift enhancement and drag reduction,while the high aerodynamic efficiency in supersonic flight mainly results from drag reduction;the aerodynamic characteristics in transonic flight conditions do not change significantly with the folding process.In addition,asymmetric folding of the external wing can also be used for maintain roll and yaw control over the entire flight envelope of the vehicle.By folding the external segment wing at different angles,the spanwise adaptive wing can adapt to different flight conditions and obtain better aerodynamic benefits,which can be applied to the next generation of subsonic or supersonic airplanes.