SURFACE TREATMENTS FOR NEXT GENERATION OF QUIET AEROFOILS

在减少翼型后缘自噪声方面的一项重大进展，最近是由弗吉尼亚理工大学的研究小组取得的，该研究小组由该项目的合作者威廉·德文波特教授和斯图尔特·克莱格教授领导。他们证明，在紊流边界层中引入“冠层”（可能由织物、金属丝或金属杆构成），可显著降低后缘附近的表面压力谱，因此也可类似地降低远场噪声。选择这些处理方法是为了重现覆盖许多猫头鹰暴露的飞羽表面的绒毛冠层。翼型自噪声通常是从升力面（例如翼型和涡轮机叶片）发出的主要噪声源，并且是英国许多战略重要部门（包括环境、能源和运输）中的主要问题。这项工作还处于早期阶段，人们对精确的控制机制知之甚少。这个为期36个月的项目涉及建立表面处理的基本物理控制机制，目的是在现实的雷诺数和攻角（AoA）下开发不会显着降低空气动力学性能的翼型几何形状的有效处理。该项目结合了先进和详细的实验以及高分辨率计算方法和高性能计算的最新进展。该项目的核心是使用一种新的湍流离壁边界条件，以精确模拟边界层和冠层表面之间的相互作用。

A major advance in the reduction of aerofoil trailing edge self-noise has recently been made by the team at Virginia Tech led by Professors William Devenport and Stewart Glegg, collaborators in this project. They demonstrated that introducing 'canopies' into the turbulent boundary layer, which may be constructed from fabric, wires, or rods, produced significant reductions in the surface pressure spectrum near the trailing edge, and hence similar reductions in the far field noise. These treatments were chosen to reproduce the downy canopy that covers the surface of exposed flight feathers of many owl species. Aerofoil self-noise is often the dominant noise source emitted from lifting surfaces, such as aerofoils and turbine blades, and is a major issue in a number of strategically important sectors in the UK, including environment, energy and transport. This work is in its early stages and the precise control mechanisms are poorly understood. This 36-month project is concerned with establishing the fundamental physical control mechanisms of surface treatments with the objective of developing effective treatments on aerofoil geometries at realistic Reynolds numbers and Angle of attack (AoA) that do not significantly degrade aerodynamic performance. The project is a combination of advanced and detailed experimentation together with the application of recent advances in high-resolution computational methods and high-performance computing. At the heart of this project is the use of a new turbulent off-wall boundary condition to allow accurate modelling of the interaction between the boundary layer and canopy surfaces.