涡波一体乘波飞行器宽速域气动优化设计研究
AERODYNAMIC OPTIMIZATION DESIGN OF THE VORTEX-SHOCK INTEGRATED WAVERIDER IN WIDE SPEED RANGE
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摘要: 涡波一体宽速域乘波飞行器通过在低速引入涡效应, 显著改善了传统乘波体在低速状态下的升阻特性, 具有在未来宽速域空天飞行器总体气动设计当中得到广泛应用的巨大潜力. 但是, 该设计方法的研究尚不完善, 特别是在基准流场建立过程中忽略了三维效应、低速效应、黏性效应以及头部/前缘的钝化效应, 因此其高低速气动特性均有优化设计的空间. 针对此问题, 本文结合高保真RANS求解器、自由变形参数化方法、鲁棒的结构网格变形方法、离散伴随方法以及序列二次规划算法, 发展了基于离散伴随的宽速域飞行器气动优化设计方法. 基于上述方法, 针对涡波一体乘波飞行器开展了兼顾低速与高超声速气动性能的三维整机气动优化设计研究, 获得了宽速域优化构型并对其进行了流动机理分析. 结果表明, 相较于初始构型, 宽速域优化构型可以将飞行器高超声速状态下升阻特性略微提升的同时, 显著增强低速状态飞行器背风面的旋涡效应, 进而使飞行器低速状态的升力和升阻比均提升10%以上, 改善了涡波一体宽速域乘波飞行器的高低速气动性能.Abstract: The vortex-shock integrated wide-speed-range waverider could significantly improve aerodynamic performances of the traditional waverider at the low-speed state by introducing vortex effect, and has potential to be widely used in the overall aerodynamic design of the wide-speed-range aerospace vehicle in the future. However, the design of the vortex-shock integrated waverider does not consider the three-dimensional effect, low-speed effect, viscous effect and head/leading edge passivation effect during the establishment of reference flow field. So it still has potential to improve the wide-speed-range performances of the vortex-shock integrated waverider with the aerodynamic shape optimization method. In order to solve this problem, this paper develops an aerodynamic optimization design method for aircraft in wide speed range based on discrete adjoint by combining high-fidelity RANS solver, free deformation parameterization method, robust structural mesh deformation method, discrete adjoint method and sequential quadratic programming algorithm. Through the method, the aerodynamic optimization design in the wide speed range based on discrete adjoint is used to carry out for the vortex-shock integrated waverider in the subsonic and hypersonic flight conditions. The optimum configuration in the wide speed range is obtained through the aerodynamic optimization design and the flow mechanism is analyzed. The results show that compared with the original configuration, the optimum one increases the lift and lift-to-drag ratio of the vortex-shock integrated waverider more than 10% at low speed, while keeping the hypersonic lift and drag aerodynamic performance of the vehicle not fall. The performance improvement of the vehicle at low speed is attributed to the significant enhancement of the leeward vortex effect, resulting in a larger area of low pressure on the leeward surface to effectively increase the lift. The research shows that the gradient optimization based on discrete adjoint could further improve the aerodynamic performances of the vortex-shock integrated wide-speed-range waverider at high and low speed.