粘性可压缩复杂外流的局部动力学诊断理论

Owing to the rapid development of modern computational fluid dynamics, it has now been possible to perform quantitative diagnosis of nonlinear complex flow fields by using their numerical solutions, to find those local dynamic structures that have key influence on the global performance of the flows, to trace their physical root, and so to achieve advanced optimal configuration design and flow control. To this end, it is necessary to combine numerical schemes of high fidality and rigorous complex flow diagnosis theories. This is also a full and quantitative utilization of huge computed flow-field data. For incompressible flow, due to the long-time effort of the present principal investigator and coworkers in the past three decades, the desired diagnosis theory has been fully developed and applied numerically to resolve difficult issues of several external and internal complex flow problems of great engineering significance. In contrast，however, for compressible viscous flows, such a theory has remained mainly untouched. The present proposed project aims at filling this blank by developing a complete set of viscous compressible theory for complex external flow diagnosis. The theory will be able to pinpoint key local flow structures from shearing process, compressing/expanding process, and entropy process, as well as their coupling, that dominate a body's aerodynamic performance (lift, drag, and moment). Numerical confirmation of the theory will be performed by a high-fidality schemes. Then the theory will be applied preliminarily to a typical complex transonic flow field with shockwaves, vortices, separation, and flow unsteadiness. The results will be directly applied in the compressible complex flow diagnostics and optimization design of aerospace aircraft.

由于当代计算流体力学（CFD）的迅速发展，人们能够根据非线性复杂流场的数值解对流场品质作出量化诊断，找出影响流动整体性能的关键局部动力学结构，追溯其物理根源，以实现先进的构形优化设计和流动控制。为此，需要把高保真的数值方法和严格的复杂流动诊断理论结合起来，既达到诊断的目的，又实现对海量流场数据充分而定量的利用。对于不可压流，经过申请人及合作者的长期努力，这样的诊断理论已经完备，并被应用来解决了若干重大工程内外流的难题。但对于可压缩的复杂粘性流动，诊断理论的主体尚未形成。本项目旨在弥补这个空白，全面发展粘性可压缩复杂外流的局部动力学诊断理论，揭示流场中对物体升阻力与力矩特性有关键影响的剪切、胀压和熵过程与相应的流动结构。本项目将对理论进行高保真数值检验，并将其用于典型的带旋涡、分离和激波及其相互作用的非定常亚跨超声速复杂流场诊断。成果将能直接用于航空航天飞行器的可压缩复杂流动诊断和优化设计。

单一性质的流体运动可分解为以涡量为特征变量的横过程即剪切过程，和以胀量或热力学变量（压力、密度、焓、熵）为特征变量的纵过程即胀压过程. 对于非线性复杂流动，这些过程在流场内部和边界上相互耦合. 本项目基于这个基本观念及其一般理论，在5年实施中围绕粘性可压缩复杂外流的机理和诊断这个主题，以理论与计算结合的方式开展了研究.主要成果为：..1.针对国内外关于升力来源种种流行的误解，阐明了不可压粘流中启动翼型升力形成的详细物理过程；根据超疏水材料的发展水平，阐明用其实现有效滑移边界以增升减阻的物理机理..2.基于流场的纵横分解，对可压缩粘性绕流阐明了其远场分区结构，完成了近场非线性合力公式及数值结果诊断，提出了统一精确的定常升阻力解析理论及其远场渐近近似，此成果填补了理论空气动力学半个多世纪的一个基础性空白..3.针对大飞机研发迫切面临的减阻问题，用动量平衡与能量平衡分别给出了定常绕流中阻力分解的严格理论及其对典型附着流与分离流气动构型的应用诊断，提出了基于尾流场断层扫描的新的阻力诊断策略..4.为理解生物外流遇到的复杂非定常气动力现象并提供便于应用的预测理论，对粘性非定常不可压和可压缩复杂绕流的合力理论做了几项创新，包括最小域冲量理论、加权压强源理论、局部诊断的伽利略不变性条件等，并用以澄清了拍动翼型产生大推力的机理与条件..5. 鉴于粘性可压缩流体的纵场动力学理论，迄今尚未像涡动力学那样发展成熟并得到广泛工程应用，还存在若干长期困惑的基础难题，提出用物理因果性追踪纵场源的原则，确认了一种普适的非线性运动学源，并找到其新的浓缩表示；除了用各种热力学变量表述理论这个常规层面，在这些变量共同的源即胀量这个层面上表述了理论，并因而揭示出若干前所未知的纵场源项...本项目研究目标超质超量完成，包括几项源头创新.项目的实施培养了五位博士.