基于非线性扰动方程的气动声学建模研究

The airframe noise from large wide-body aircraft turns to be more significant than the engine noise and becomes the dominant noise source, due to the reduced engine power when the aircraft is at the landing configuration. Therefore, the investigation of airframe noise had become a major research aera since the end of last century. It is generally recognized that the numerical simulations for the aerodynamic noise have the potential advantages against the traditional wind-tunnel measurement in terms of efficiency and cost, and are expected to play irreplaceable roles in designing the quiter aircrafts of the next generation. This project, under the circumstances of the national project for the development of large aircrafts, aims to study the computational methods for the airframe noise predictions, which is efficient at the aircraft design stage. Based on the non-linear disturbance equations, it is expected to establish the numerical strategies, including the fast mesh generation, high order accurate interpolation, etc., for the aeroacoustic computations with the complex engineering geometries.

大型宽体飞机在降落阶段，由于发动机降低功率，机体气动噪声已经超过发动机噪声成为最主要的噪声源。因此，研究机体气动噪声已经成为飞机气动噪声研究的重要发展方向。气动噪声的计算模拟由于其潜在的效率和成本上的优势，将会在下一代更安静飞机的设计中发挥不可替代的作用。本项目基于国家大飞机发展工程，研究适用于飞机设计阶段的机体气动噪声快速计算预测方法。我们将基于非线性扰动方程，探索建立一套包含网格快速生成、高精度网格插值在内的面向实际工程问题中复杂几何体气动噪声的计算策略。

本项目中结合非线性扰动方程和FWH积分方程建立了气动噪声计算模型。基于此模型对高仿真度的起落架模型进行了辐射噪声预测，气动与声学的计算结果都与实验数据匹配很好，证明了结合OpenFOAM求解器的流场解和FWH积分可以对复杂几何的气动辐射噪声进行准确的预测。通过积分面分解，我们分析了起落架各组成部件对整体噪声的贡献，进一步揭示了起落架辐射噪声的产生机理，为下一步的控噪减噪提供了数据支持。我们基于径向基函数方法，提出了空间网格分层逐步变形方法，解决了传统基函数方法在大网格变形时的效率问题，为网格变形技术在复杂几何网格设计上的应用提供了算法基础。