TOWARDS WHOLE SPECTRUM JET NOISE PREDICTION

在航空运输快速增长的推动下，世界民用飞机机队的规模几乎每20年翻一番。英国主要机场面临越来越大的压力，需要增加额外的新跑道。飞机噪音对当地环境的影响是深远的，特别是在机场周围地区。在最坏的情况下，噪音可能不仅仅是令人讨厌的，可能是导致高血压等疾病的一个因素。在欧洲航空研究与创新咨询理事会（ACARE）制定的最新FlightPath 2050噪声排放目标中，到2050年，飞行飞机的感知噪声排放将相对于2000年的水平减少65%。这对航空航天工业来说是一个巨大的雄心和巨大的挑战，可能会将噪声研究推向前沿。允许起飞噪声水平的持续降低也使得现有的技术和更成熟的飞机/发动机模型过时，为拟议的工作提供了强大的经济意义。基于大涡模拟（LES）的喷气噪声数值预测在研究界和工业界都变得越来越有前途。尽管LES预测与声学实验相比通常更经济实惠，但它仍然耗时且昂贵，通常需要大量高性能计算（HPC）资源，以便捕获低频和高频噪声频谱。这被称为尺度差异，并且显然阻止了基于LES的噪声预测方法进一步应用于更复杂和现实的工业喷气机配置。为了规避这一障碍的规模差距，提出的工作的目的是探索一种新的方法相结合的噪声频谱（在频谱空间）从LES解决方案与不同的网格分辨率在物理空间中获得的潜在优势。目前的工作扩展了最近完成的非常成功的EPSRC项目GR/T06629/01中开发的方法，其中申请人是首席研究员，以及正在进行的罗尔斯·罗伊斯/TSB资助的SILOET计划喷气噪声项目。从这项工作中获得的结果将对美国宇航局的实验数据，以及从一个完整的长度采样细网格单LES解决方案的结果进行基准。这项工作还将通过对分解流场的低通滤波分析、速度结构函数和湍流动能谱的评估来研究从较小涡到较大涡的湍流能通量。

Driven by the rapid growth in air transport, the world's civil aircraft fleet is almost doubling in size every two decades. Major UK airports are under increasing pressure to add extra new runways. The impact of aircraft noise on the local environment is profound especially in the surrounding areas of an airport. In the worst case noise can be more than just annoying, potentially being a contributory factor towards illnesses such as hypertension. In the latest FlightPath 2050 noise emission targets, set by the Advisory Council for Aviation Research and innovation in Europe (ACARE), the perceived noise emission of flying aircraft is to be reduced by 65% relative to levels of 2000 by 2050. This is a huge ambition and tremendous challenge to the aerospace industry, potentially putting noise research to the forefront. Continuing reductions in permitted take-off noise levels are also making the existing technology and more established plane/engine models obsolete giving the strong economic implications for the proposed work.Large Eddy Simulation (LES) based numerical prediction of jet noise has become increasingly promising in both research communities and industry. Despite LES prediction being generally more affordable compared to acoustic experiments, it is still time consuming and costly, often requiring significant High Performance Computing (HPC) resources, in order to capture both low- and high-frequency noise spectra. This is known as the scale disparity, and clearly is preventing LES based noise predictive methods from being further applied to more complex and realistic industrial jet configurations. To circumvent this obstacle of scale disparity, the work proposed aims to explore the potential advantages of a novel approach of combining noise spectra (in the spectral space) obtained from LES solutions with different grid resolutions in the physical space. The current work extends the methodology developed in the recently completed and highly successful EPSRC project GR/T06629/01, in which the applicant being the lead researcher, and the ongoing Rolls-Royce/TSB funded SILOET programme jet noise project. Results obtained from this work will be benchmarked against NASA experimental data as well as results from a full length sampling fine-grid single LES solution. The work will also investigate turbulent energy flux directed from smaller eddies to larger ones by a low-pass filtering analysis of the resolved flow field, the evaluation of velocity structure function and turbulent kinetic energy spectra.