Session: 11-01: Alternative Energy Converstion Technology (including Wind, Geothermal, Hydro, and Ocean)

Paper Number: 155423

155423 - Numerical and Experimental Investigation of a Trailing Edge Noise Generated by Naca 0012 Airfoil at Low Reynolds Numbers 

Abstract: 

In the modern world, more and more attention is paid to solving environmental problems, in particular, to the development and implementation of technologies for reducing the negative impact of industrial noise pollution on the environment. One of the most common sources of noise pollution is aerodynamic noise, which is created by the air flow around the structural elements of technical devices. For example, such noise occurs during the operation of high-speed vehicles, aircraft, industrial equipment, wind turbines. This study presents the results of numerical and experimental analysis of aerodynamic noise generated by flow around a NACA0012 airfoil at low Reynolds numbers, the source of which is the interaction of vortex structures with the trailing edge of the airfoil. The main attention is paid to tonal noise, which occurs in transient flow regimes.

The numerical study was performed using the direct numerical modeling approach based on the ANSYS Fluent package, using the large eddy simulation (LES) method to simulate the turbulent flow field. This approach allows for more accurate modeling of turbulent structures occurring near the airfoil surface. The simulation was performed using high-precision spatial discretization, which ensures the resolution of small vortex structures that play a key role in noise generation. The simulation was performed for a range of Reynolds numbers of about 1.0-1.6 10⁵, which corresponds to the real operating conditions of small and medium-sized wind turbine blades.

The experimental studies were carried out on two setups located in anechoic chambers. The first series of experiments was carried out on a setup developed at Western Michigan University using a wind tunnel and a test profile, which was installed between two side plates to minimize the influence of edge effects. In the second series of experiments, performed at Dnipro University of Technology, a setup device was used which allowed reproducing the rotational motion of a wind turbine blade segment. In this case, the experiments used sound level meters of accuracy class IEC 61672-1:2013, which made it possible to achieve high accuracy in measuring acoustic characteristics. Acoustic data were recorded using highly sensitive microphones, and subsequent spectral analysis was performed using the fast Fourier transform (FFT) method.

The results of numerical and experimental modeling using the NACA0012 airfoil showed a high degree of agreement. Thus, for conditions corresponding to Re = 1.6 10⁵, the main tonal noise was recorded at frequencies of about 1200 Hz both in the experimental data and in the numerical calculations, while the secondary tones also demonstrated good correlation. The discrepancy in the sound pressure level between the experiments and two-dimensional calculations was about 15 dB, which corresponds to the known results obtained in works on two-dimensional modeling of aerodynamic noise.

An important result of the study was the confirmation of the possibility of using the ANSYS Fluent package for direct numerical modeling of aerodynamic noise with sufficient accuracy for engineering applications. Modeling using LES and a high-precision mesh demonstrated the ability to reproduce the main physical mechanisms of noise generation, such as the formation of vortices on the trailing edge of the profile and their interaction with the main jet. This opens up prospects for further application of these methods in the development and optimization of designs for noise reduction.

In the future, it is planned to expand the research to three-dimensional settings, which will allow taking into account additional factors, such as tip vortices and more complex flow regimes. The results obtained can be used in the development of noise reduction technologies in various engineering applications, such as wind energy, aviation, and high-speed transport.

Presenting Author: Rishav Mishra Western Michigan University

Presenting Author Biography: The presenting author is a graduate student at Western Michigan University.