具有锯齿型尾缘翼型的湍流结构演化、时空关联与声源特性研究

The problem of airfoil noise is widely existed in aircraft of military and commercial planes, which is the one of the important noise sources. The design of sawtooth serrated trailing edges can reduce the airfoil noise to some extent. To investigate noise reduction mechanism of sawtooth serrated trailing edges is of scientific significance, which can also provide theoretical guidance for engineering applications. Previous works have confirmed that the application of specific sawtooth serrated trailing edges can reduce noise emission. Parametric studies were performed for the design of the geometry of sawtooth, however, no consistent standard is achieved for the design of the sawtooth geometry and some controversy about the mechanism of noise reduction also exists. This project is dedicated to perform large eddy simulation of flow past an airfoil with the sawtooth serrated trailing edge using high-resolution numerical schemes, and to study the generation and evolution of the turbulent structures near the trailing edge, besides its characteristics of noise radiation. Special attention will be paid on the space-time correlations of turbulence structures, and we will assess the existed space-time correlation models and attempt to develop a more applicable model. We will study mechanism of noise sources in such a flow, and then to reveal the underlying mechanisms of noise reduction with the application of sawtooth serrated trailing edges, based on the relationship between the turbulent flow structures and noise source structures.

翼型噪声广泛存在于军用和民用航空飞行器中，是重要的气动噪声源之一。锯齿形尾缘设计能够一定程度上降低翼型噪声，研究其降噪机理具有重要的科学意义，并可为工程应用提供理论指导。前人的工作已表明特定的锯齿形尾缘构型能够降低噪声辐射，并对锯齿的构型进行了参数研究，但尚未形成统一的构型设计标准，关于降噪机理也仍存在一定争议。本项目首先采用高精度数值方法对具有锯齿形尾缘的翼型的绕流进行大涡模拟，研究尾缘附近湍流结构的生成和演化及其噪声辐射特性。重点关注湍流结构的时空关联特性，考核现有时空关联模型并发展适用更广的模型。研究流动的声源特性，根据湍流结构和声源结构间的关系，揭示锯齿形后缘的降噪机理。

翼型尾缘噪声控制是大飞机、风力发电机等工业领域降噪设计的关键问题之一。本项目基于隐式大涡模拟开展了锯齿尾缘翼型绕流流动的高精度模拟，系统分析了锯齿结构对翼面压力脉动相干性的影响，并基于多过程声学理论给出了近场流动声源的分布特性，系统揭示了锯齿降噪的内在机制；在机理认识基础上，设计了多种曲边尾缘锯齿，并分析了曲边尾缘锯齿对噪声和湍流结构演化的影响规律，阐释了曲边锯齿的主导降噪机理，并找出了降噪最优的曲边齿形；结合多孔介质和尾缘锯齿开展了复合降噪控制，发现其降噪潜力更大，但同时会损失一定的气动性能；研究了高阶有限差分算法求解器在现代GPU异构平台上的加速策略，取得了超过500倍的加速比。此外，进一步开展了射流噪声控制、方腔噪声控制、可压缩边界层压力脉动生成演化机制等研究，并分析了其中的物理机制。通过本项目的研究可以为潜在的工程应用提供可靠的理论指导。

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