A numerical study on aerofoil trailing edge noise and its reduction methods for the next-generation wind turbines

近年来风能产量的快速增长已经到了这样一个阶段，为了成功地继续增加风力发电机组的规模和降低能源成本(COE)，风力发电机组的气动噪声排放是一个关键问题。解决气动噪声问题的基本原则是以这样一种方式设计涡轮叶片，即在不改变叶片的气动效率的情况下减轻噪声源，而叶片的气动效率对COE至关重要。实现这种噪声-噪声叶片设计的最有效方法之一是在噪声发射最强的叶片的后缘(在运行条件下)使用“锯齿”。维斯塔斯(全球最大的风力涡轮机制造商之一)近年来已成功开发出锯齿形后缘(STE)叶片，目前已投入使用。然而，对STES的研究仍然不发达，有许多领域需要更好地理解和改进现有的STES。Vestas的目标是在未来几年内在STE的开发上取得重大突破，以便在他们的下一代风力涡轮机中成功实施该技术。南安普顿大学拟议的博士项目是Vestas开发下一代STE的多学科计划的一部分。这一特定的PHD项目旨在实现对STES产生和降低噪声的物理机制的详细了解，并推导出一个半经验工程模型，该模型提供了在不同几何形状和流动条件下通过STES降低噪声的预测。该项目将主要基于数值模拟(大涡模拟)和对预测模型的一些数学推导。大涡模拟将使用南安普顿大学开发的内部代码CARARD(可压缩空气动力学和气动声学研究代码)进行。代码基于高阶有限差分方法，并在MPI平台上完全并行(运行在国家超级计算机Archer以及具有超线性可伸缩性的本地IRIDIS-4集群上，处理器内核高达10,000+)。有关计算工作的更多相关信息可在https://doi.org/10.1017/jfm.2016.841.中找到

The rapid growth of wind energy production in recent years has reached a stage where the aerodynamic noise emission from wind turbines is a critical issue to overcome in order to successfully continue increasing the scale of the turbines and reducing the cost of energy (CoE). The fundamental principle to tackle the aerodynamic noise issue is to design the turbine blades in such a way that the source of noise is alleviated without changing the aerodynamic efficiency of the blades that is critical for CoE. One of the most effective ways to achieve such a noise-noise blade design is to use "serrations" on the trailing-edge of the blades from which the noise emission is strongest (at an operating condition). Vestas (one of the largest wind-turbine manufacturers in the globe) has been successful in developing blades with serrated trailing-edges (STEs) in recent years and they are in service now. However, the research on STEs is still underdeveloped and there are various areas where STEs should be better understood and improved upon what they are at present. Vestas aims to make a major breakthrough in the development of STEs within the next a few years in order to successfully implement the technology in their next-generation wind turbines.The proposed PhD project at the University of Southampton is part of the Vestas multidisciplinary programme for the development of next-generation STEs. This particular PhD project aims to achieve detailed understandings of the physical mechanisms of the noise generation and its reduction due to the STEs, and to derive a semi-empirical engineering model that provides predictions of the noise reduction through the STEs for various geometries and flow conditions. The project will be carried out mainly based on numerical simulations (large-eddy simulations) and some mathematical derivations for the prediction model. The large-eddy simulations will be performed by using an in-house code CANARD (Compressible Aerodynamic & Aeroacoustic Research coDe) developed at the University of Southampton. The code is based on high-order finite-difference methods and is fully parallelised on an MPI platform (running on the national supercomputer ARCHER as well as the local IRIDIS-4 cluster with a supra-linear scalability with up to 10,000+ processor cores). Some more relevant information about the computational work can be found in https://doi.org/10.1017/jfm.2016.841.