Aerodynamic Research for the Next Generation Supersonic Transport

本文对下一代超音速输运的气动问题进行了研究，取得了以下成果。开发了一种基于非结构网格的CFD程序，用于高效、准确地评估飞机的气动性能。这包括几个新的方案，如利用CAD数据的表面/体网格生成方法和非结构网格上的隐式时间积分。应用CFD程序对NAL实验超音速飞机上升段的气动系数进行了计算。数值结果揭示了跨音速飞行过程中产生高升力的原因。对NAL实验超音速飞机与火箭助推器的分离过程进行了数值模拟，并用一种新的叠置网格方法得到了分离过程中的气动系数。该方案是评价飞机动态稳定性的一种很有前途的…方法。好多了。为了研究超音速运输机的起降气动性能，采用自适应加细和涡心识别的方法，建立了一种预测三角翼涡控绕流的数值方法。结果表明，该方法能够准确预报大攻角下的旋涡破裂。将原来的跨声速机翼反设计方法推广到超音速机翼。利用该程序对NAL实验超音速飞机的主翼进行了设计，实现了机翼上表面自然层流的放大，从而改善了L/D的性能。利用非结构网格方法编制了高效的伴随优化程序，并将其应用于机翼单独布局、机翼-机身、机翼-机身-机舱布局的气动优化问题，以及跨音速巡航时机翼-机身布局的襟翼角度优化问题。提出了一种改进的多目标遗传算法，并将其应用于超音速机翼的设计。考虑了四个设计目标：最小超音速和跨音速巡航条件下的气动阻力，以及最小俯仰力矩和根部弯矩。设计结果表明，一种新型的箭翼布局在各项设计指标上都具有良好的性能。较少

In this study, aerodynamic problems related to the next generation supersonic transport have been investigated and the following results were obtained.1. A CFD code based on the unstructured grid to efficiently and accurately evaluate the aerodynamic performance of airplanes was developed. This includes several new schemes such as the surface/volume grid generation methods using the CAD data and the implicit time integration on unstructured grid.2. The CFD code was applied to evaluate the aerodynamic coefficients of the NAL experimental supersonic airplane in ascent flight. Numerical result revealed the cause of the high lift production during the transonic flight regime.3. The separation process of the NAL experimental supersonic airplane from the rocket booster was numerically simulated and the aerodynamic coefficients during the separation were obtained by a newly developed overset grid method. This scheme is a promising approach to evaluate the dynamic stability of the airplane as … More well.4. For aerodynamic investigations of the takeoff/landing performance of a supersonic transport, a numerical scheme to predict vortex-dominated flows over delta wings were developed using the adaptive refinement and the vortex-center identification. This scheme was shown to be effective to accurately predict the vortex breakdown at high angle of attack.5. An inverse design method originally developed for transonic wings was extended to supersonic wings. With this code, the main wing of the NAL experimental supersonic airplane was designed to realize the enlarged natural laminar flow on the upper surface of the wing for improved L/D performance.6. An efficient adjoint optimization code has been developed using the unstructured grid approach, The resulting code has been used for aerodynamic shape optimization problems of wing alone, wing-fuselage, and wing-fuselage-nacelle configurations, as well as flap angle optimization on the wing-fuselage configuration at transonic cruise.7. An improved multiobjective genetic algorithm has been developed and applied to the supersonic wing design. Four design objectives were considered : minimizations of aerodynamic drag both at supersonic and transonic cruise conditions as well as minimizations of pitching moment and root-bending moment. The design results indicate that a new type of "arrow wing" configuration has good performances in all design objectives. Less