Application of computational aeroacoustics for the investigation of acoustic diffraction effects along airfoil trailing edges

Abstract

Airfoil trailing edges represent a fundamental mechanism of aerodynamic noise generation. The physical process of noise generation in an airfoil trailing edge occurs when turbulent structures are advected along the boundary layer, producing velocity fluctuations near the trailing edge. These fluctuations induce further aerodynamic pressure fluctuations that can be scattered by the solid surface of the airfoil. Thus, aerodynamic energy of the flow is converted into acoustic energy propagated in the form of waves which are diffracted at the trailing edge.The study of noise generation in airfoil trailing edges finds application in several problems of scientific and industrial interest such as in aircraft wings, wind turbine blades and fans found in electronic cooling systems. In the first case, the airfoil noise can be generated by deployed slats and flaps for aircraft landing, when these surfaces are extended to provide high lift. Furthermore, jet noise may suffer diffraction along wing trailing edges.With the increasing size of aircraft engines, the jet noise diffraction problem became relevant. In order to reduce fuel consumption in aircraft engines, the industry has chosec to increase the ratio between cold and hot flow regions of the jets. This has approached the engines from the wings to keep a safe distance between the propulsion system and the ground. However, with the engine approach, the jet flow is developed in the proximity to the trailing edge. Furthermore, at takeoff and landing conditions, flaps are extended and interact with the jet flow causing additional noise sources.In this work, computational aeroacoustics will be applied to investigate the diffraction effects of acoustic waves along airfoil trailing edges. In this context, high-fidelity simulations will be used to study the noise sources present in installed jet configurations. In addition, reduced order models will also be developed and used to better understand the noise installation problem.