各向异性湍流所产生前缘宽频干扰噪声关键科学问题研究

We plan to conduct a fundamental aeroacoustic study of broadband noise produced by anisotropic turbulence interacting with a generic lifting surface, e.g. an aerofoil. This problem has both scientific merits and wide engineering significance. This fundamental problem is widely called “leading edge noise” problem. It can be found in noise problems of aero-engine fan-outlet guide vane interaction, rotors, airframe, high speed transport, etc., as well as and silent flight of birds. Current predictive methods based on flat plate theories and isotropic turbulence assumptions suffer from restrictive and inadequate assumptions; experimental databases are often collected in small and poor quality facilities in the west, with parameters that are decoupled from theories; expensive direct simulation of turbulence suffer from cost and does not permit sufficient parameter range that is pertinent to design. Based on our previous research and expertise, we now proposed a framework of research based on analytical and computational aeroacoustics, supported by new experiments in modern facilities that overcome the limitation in facilities outside China. The analytical research will develop a new formulation for sound extrapolation to far-field under the existence of both acoustic and vortical disturbances, that cannot be solved by existing methods, and also a generic digital filter method for synthetic turbulence that overcomes limitation on the need for ad hoc selection discrete eddies and Mach number dependence. The computational aeroacoustics work will concentrate on high quality mesh and new non-reflective boundaries to develop a new software. The experimental studies will focus on anisotropic turbulence and extended observation angle range in two modern facilities, leading new database and physical insight. Outcome of the project will be a computational code and high-quality data. Successful completion of the project will aid Chinese aerospace industry.

翼型前缘宽带气动噪声源于湍流与升力面翼型相互作用，对其研究能帮助降低发动机旋转机械和飞机机体噪声、理解鸟类低噪声飞行的物理机理，是国际航空界前沿热点研究问题之一。当前，相关理论模型和工业预测工具主要基于平板和各向同性湍流假设，为进一步研究各向异性湍流下的前缘噪声理论，还需要发展高品质的风洞测试技术及高效模拟方法。为此，我们将综合发展理论分析、数值模拟和试验手段，研究适用于湍流中的基于脱体积分面的远场声辐射预测方法，通过开发网格质量动态控制新方法、以及高效的气动噪声无反射边界条件来发展高效的计算工具，最后通过风洞实验精细测试气动声源、考察各向异性湍流对气动性能和气动噪声的影响，并阐释相关流体力学物理机制。总的来说，我们会聚焦气动声学前沿问题，深入研究前缘宽带噪声的物理机制和理论模型，发展高效的模拟软件和试验技术并建立标模实验数据库，为航空重大专项探索前沿技术、提供科学方法保障做出贡献。

本项目研究背景为发动机旋转机械和飞机机体、鸟类飞行等升力面与湍流相互作用产生宽带气动噪声的问题。该课题是国际航空界前沿热点研究问题之一。当前，相关理论模型和工业预测工具主要基于平板和各向同性湍流假设。同时，在计算过程中，由于湍流脉动、声波脉动等问题，对边界条件以及远场噪声计算方法等都存在一定困难。在本项目中，我们深入研究了各向异性湍流下的前缘噪声理论，开发了高效、准确、不依赖流动参数的湍流合成方法。同时基于高品质风洞，进行了一系列试验测量。我们提出了一种直接的数值滤波方法，可以直接生成不同各向异性、具有一般表达式湍流谱的湍流脉动，并开展了系统的参数化研究，考察了各个方向湍流脉动、积分长度，流动状态以及不同翼型的影响。还发展了理论方法考察了真实翼型的非均匀流动对噪声在上下游观测点处噪声结果的影响，提出新型数学处理办法。 同时，我们综合发展理论分析、数值模拟和试验手段，研究适用于湍流中的基于脱体积分面的远场声辐射预测方法，并且为发展新型的三阶声比拟理论打下了基础。在数值方法上，我们开发了高效的气动噪声无反射边界条件来发展高效的计算工具，并运用到了实际的气动声学问题之中。其中不同湍流谱脉动与不同翼型相互干扰的流动结果是本研究的关键数据。研究内容聚焦了气动声学前沿问题，深入理解了前缘宽带噪声的物理机制，并发展了理论模型，为航空重大专项探索前沿技术、提供科学方法保障做出贡献。