Effect of porosity on Curle's dipolar sources on an aerofoil in turbulent flow

Integrating a porous material into the structure of an aerofoil constitutes a promising passive strategy for mitigating the noise from turbulence–body interactions that has been extensively explored in the past few decades. When a compact permeable body is considered in the aeroacoustic analogy derived by Curle to predict this noise source, a...

On the extension of k−ω−SST corrections to predict flow separation on thick airfoils with leading-edge roughness

Modern wind turbines employ thick airfoils in the outer region of the blade with strong adverse pressure gradients and high sensitivity to flow separation, which can be anticipated by leading-edge roughness. However, Reynolds average Navier-Stokes simulations currently overpredict the Reynolds shear stresses near the surface, and the flow...

Numerical Simulation of Grid-Generated Turbulence Interaction with a NACA0012 Airfoil

The present study assesses the ability to numerically predict turbulence-interaction noise of a NACA0012 airfoil with grid-generated turbulence by utilizing the Lattice Boltzmann solver PowerFLOW. Both the near-field flow characteristics and far field noise are bench-marked against an existing experimental study. The grid was chosen to match...

Turbulence-distortion analysis for leading-edge noise-prediction enhancement

The analytical model for leading-edge noise prediction formulated by Amiet, developed for a flat plate, relates the far-field acoustic pressure to the upstream inflow conditions, modeled by canonical turbulence spectra. The inaccurate results provided by this low-fidelity method when applied to thick airfoils has been attributed to the...

Jet-Installation Noise Reduction with Permeable Flaps at In-Flight Conditions

An experimental investigation on jet-installation noise reduction with permeable flaps on an aircraft half-model is performed, focusing on the effects on the noise levels as well as on the aerodynamic properties of the model (lift and drag forces). A nozzle with an exit diameter = 113 mm is included for generating a single-stream jet flow in...

On the Aerodynamic-Noise Sources in a Circular Cylinder Coated with Porous Materials

Coating a circular cylinder with porous materials constitutes an effective passive strategy for reducing the flow-induced noise linked to the vortex shedding. Despite the number of investigations in the last decade, the noise-mitigation mechanisms associated with this technique remain unclear. The present research aims to clarify the role played...

Development of the SmartAnswer Demonstrator: a Didactic Wind Tunnel for Aeroacoustic Applications^∗

A small didactic wind tunnel demonstrator has been designed and manufactured at the von Karman Institute for Fluid Dynamics to illustrate the physical principles at stake in flow-induced noise generation, offer an audible perception of the effectiveness of noise-mitigation strategies, and serve as a practical test bench for aeroacoustic...

Investigation of Curle's Dipolar Sources on a Porous Airfoil Interacting with Incoming Turbulence

Integrating porous materials into the structure of an airfoil constitutes a promising passive strategy for mitigating the noise from turbulence-body interactions that has been extensively explored in the past few decades. When a compact permeable body is considered in the aeroacoustic analogy derived by Curle to predict this noise source, a...

Sound localization and quantification analysis of an automotive engine cooling module

Sound emissions of an automotive engine cooling system are studied using both single-microphone directivity measurements and a rotating beamforming technique. These measurements provide reference acoustic data on such a system and some new understanding of the effect that the radiator induces on the distribution of sound sources. Indeed, the...

Investigation of turbulence-surface interaction noise mechanisms and their reduction using porous materials

The interaction of an airfoil with incident turbulence is an important source of aerodynamic noise in numerous applications, such as turbofan engines, cooling systems for automotive and construction industries, high-lift devices on aircraft wings, and landing gear systems. In these instances, turbulence is generally produced by elements that are...

Experimental and Analytical Investigation of the Distortion of Turbulence Interacting with a Porous Airfoil

View Video Presentation: https://doi-org.tudelft.idm.oclc.org/10.2514/6.2021-2289.vid<br/><br/>A possible strategy for the reduction of the aeroacoustic noise generated by turbulence interacting with a wing profile, also referred to as leading-edge noise, is represented by the implementation of a porous medium in the structure of the airfoil....

Jet-installation noise reduction with flow-permeable materials

This paper investigates the application of flow-permeable materials as a solution for reducing jet-installation noise. Experiments are carried out with a flat plate placed in the near field of a single-stream subsonic jet. The flat plate is modular and the solid surface near the trailing edge can be replaced with different flow-permeable...

Experimental investigation of turbulent coherent structures interacting with a porous airfoil

Abstract: The flow field on solid and porous airfoils subjected to turbulence shed by an upstream cylindrical rod and the corresponding far-field noise radiations are studied through particle image velocimetry (PIV) and microphone measurements, respectively. Three different Reynolds numbers based on the rod diameter are considered in a range...

Assessment of the accuracy of microphone array methods for aeroacoustic measurements

In this paper, the performance of four acoustic imaging methods: conventional frequency domain beamforming (CFDBF), functional beamforming (FUNBF), enhanced high resolution CLEAN–SC (EHR–CLEAN–SC) and generalized inverse beamforming (GIBF), is investigated in terms of accuracy and variability. Three experimental test cases are considered: 1)...

On the role of turbulence distortion on leading-edge noise reduction by means of porosity

A possible strategy for the reduction of the aeroacoustic noise generated by turbulence interacting with a wing profile, also referred to as leading-edge noise, is represented by the implementation of a porous medium in the structure of the airfoil. However, the physical mechanisms involved in this noise mitigation technique remain unclear....

Experimental investigation of airfoil turbulence-impingement noise reduction using porous treatment

The present work aims at evaluating the effectiveness of the use of porous materials for reducing airfoil turbulence-impingement noise. To pursue this objective, a porous NACA-0024 profile filled with melamine foam has been designed for comparison with a solid model. The porous media constituting the airfoil has been fully characterized in...

Integration methods for distributed sound sources

Most acoustic imaging methods assume the presence of point sound sources and, hence, may fail to correctly estimate the sound emissions of distributed sound sources, such as trailing-edge noise. In this contribution, three integration techniques are suggested to overcome this issue based on models considering a single point source, a line...