scholarly journals Mechanisms of broadband noise generation on metal foam edges

2019 ◽  
Vol 31 (10) ◽  
pp. 105110 ◽  
Author(s):  
Alejandro Rubio Carpio ◽  
Francesco Avallone ◽  
Daniele Ragni ◽  
Mirjam Snellen ◽  
Sybrand van der Zwaag
Keyword(s):  
Metal Foam ◽  
Broadband Noise ◽  
Noise Generation

Broadband Noise Generation by a Vortex Model of Cavity Flow

AIAA Journal ◽  
1977 ◽  
Vol 15 (5) ◽  
pp. 632-637 ◽  
Author(s):  
Jay C. Hardin ◽  
Jean P. Mason
Keyword(s):  
Cavity Flow ◽  
Broadband Noise ◽  
Noise Generation ◽  
Vortex Model

scholarly journals Trailing Edge Thickness Effect on Tonal Noise Emission Characteristics from Wind Turbine Blades

2021 ◽  
Vol 13 (4) ◽  
pp. 99-111
Author(s):  
Satya Prasad MADDULA ◽  
Vasishta Bhargava NUKALA ◽  
Venkata Swamy Naidu NEIGAPULA
Keyword(s):  
Wind Turbine ◽  
Power Level ◽  
Turbine Blades ◽  
Broadband Noise ◽  
Thickness Effect ◽  
Sound Power ◽  
Noise Generation ◽  
Wind Turbine Blades ◽  
Trailing Edge ◽  
Sound Power Level

Broadband noise generation from wind turbine blades is one of the fundamental aspects of flow-induced noise. Besides the turbulent boundary layer flow over the blades, factors such as the angle of attack, the turbulence intensity, the trailing edge thickness of the blade and their shapes strongly influence the overall sound power levels at high frequencies, i.e. f > 8 kHz. In large operating wind farms, a trade-off between noise generation and power production is considered by power utility firms to maximize the return on investment (ROI) and minimize the fatigue damage on wind turbine components. The present work deals with the analysis of the thickness effect on trailing edge bluntness noise level at hub height average wind speeds of 7 m/s, 10 m/s. A semi-empirical BPM model was used to predict the sound pressure levels from the 37 m blade length of a 2MW wind turbine. The receiver configuration was fixed at a distance of 120 m from the source height of 80 m. The results demonstrated that as the trailing edge height increased from 0.1 % to 0.5 % of the local chord, the sound power level increased by ~ 17 dB for frequencies > 200 Hz, but decreased by 16 dB when the thickness is 0.1 % local chord. The computed results of the sound power level using the BPM model have been validated using experimental data and showed a good agreement for the tonal frequencies, f ~ 10 kHz, where the trailing edge bluntness noise becomes dominant.

scholarly journals Acoustic characteristics of a ported shroud turbocompressor operating at design conditions

2018 ◽  
Vol 21 (8) ◽  
pp. 1454-1468 ◽  
Author(s):  
Sidharath Sharma ◽  
Alberto Broatch ◽  
Jorge García-Tíscar ◽  
John M Allport ◽  
Ambrose K Nickson
Keyword(s):  
Decomposition Methods ◽  
Broadband Noise ◽  
Stable Operation ◽  
Noise Generation ◽  
Noise Emission ◽  
Spectral Signatures ◽  
Surge Margin ◽  
Flow Enhancement ◽  
Ported Shroud ◽  
The Impact

In this article, the acoustic characterisation of a turbocharger compressor with ported shroud design is carried out through the numerical simulation of the system operating under design conditions of maximum isentropic efficiency. While ported shroud compressors have been proposed as a way to control the flow near unstable conditions in order to obtain a more stable operation and enhance deep surge margin, it is often assumed that the behaviour under stable design conditions is characterised by a smooth, non-detached flow that matches an equivalent standard compressor. Furthermore, research is scarce regarding the acoustic effects of the ported shroud addition, especially under the design conditions. To analyse the flow field evolution and its relation with the noise generation, spectral signatures using statistical and scale-resolving turbulence modelling methods are obtained after successfully validating the performance and acoustic predictions of the numerical model with experimental measurements. Propagation of the frequency content through the ducts has been estimated with the aid of pressure decomposition methods to enhance the content coming from the compressor. Expected acoustic phenomena such as ‘buzz-saw’ tones, blade passing peaks and broadband noise are correctly identified in the modelled spectrum. Analysis of the flow behaviour in the ported shroud shows rotating structures through the slot that may impact the acoustic and vibration response. Further inspection of the pressure field through modal decomposition confirms the influence of the ported shroud cavity in noise generation and propagation, especially at lower frequencies, suggesting that further research should be carried out on the impact these flow enhancement solutions have on the noise emission of the turbocharger.

Towards Computational Prediction of Wind Turbine Flow and Noise

2017 ◽  
Author(s):  
Cheng Zhang ◽  
Murilo Basso
Keyword(s):  
Wind Energy ◽  
Wind Turbine ◽  
Local Community ◽  
Broadband Noise ◽  
Aerodynamic Noise ◽  
Cfd Modeling ◽  
Computational Domain ◽  
Noise Generation ◽  
Upwind Schemes ◽  
The Impact

Wind energy is a clean, renewable, and fast-growing energy source for power generation. However, the noise issue, especially the aerodynamic noise, has become a critical obstacle in wind energy development. To determine the impact of the wind turbine noise and to guide the design and siting of wind turbines to minimize the disturbances on the local community, better understanding of the noise generation mechanisms as well as more accurate noise prediction techniques are necessary. Computational fluid dynamics (CFD) modeling of the National Renewable Energy Laboratory (NREL) Phase VI wind turbine at different wind speeds and tip pitch angles have been performed using ANSYS Fluent. The computational domain extends about 3 times of the wind turbine blade radius in the upstream direction, and 6 times the blade radius in the downstream and transverse directions. The shear-stress transport (SST) k-omega turbulence model is used. Second-order upwind schemes are used for the momentum and turbulence equations. The predicted pressure coefficients and power are in good agreement with the experimental data. The effects of wind speed and tip pitch angle on noise generation have also been investigated using the broadband noise source model. The Ffowcs-Williams Hawkings equation is also currently being used to obtain the far-field noise.

Modeling of the Broadband Noise Radiated by an Airfoil

2004 ◽  
Author(s):  
Djaafer Fedala ◽  
Smai¨ne Kouidri ◽  
Farid Bakir ◽  
Robert Rey
Keyword(s):  
Prediction Method ◽  
Leading Edge ◽  
Acoustic Power ◽  
Broadband Noise ◽  
Noise Generation ◽  
Unsteady Aerodynamic ◽  
Turbulence Flow ◽  
Power Spectral ◽  
Linearized Theory ◽  
Complex Phenomena

The mechanisms of noise generation due to the turbulent flow around an airfoil are complex phenomena. In this paper, a prediction method of the broadband noise is presented then validated. The aim of this work is to develop tools of noise prediction in turbomachinery engaged by the laboratory since several years. The modeling presented is based on the unsteady aerodynamic linearized theory of an airfoil. An acoustic calculation based on the formulation of Amiet determines the far field acoustic power spectral density produced by an airfoil. It shows the importance of the noise due to the interaction of incident turbulence flow with the leading edge. The results obtained are compared with the experimental results available in the literature.

Modeling and Analysis of Aerodynamic Noise in Milling Cutters

2006 ◽  
Vol 129 (1) ◽  
pp. 5-11 ◽  
Author(s):  
Karthikeyan Sampath ◽  
Shiv G. Kapoor ◽  
Richard E. DeVor
Keyword(s):  
High Speed ◽  
Noise Exposure ◽  
Noise Spectrum ◽  
Rotational Frequency ◽  
Face Milling ◽  
Broadband Noise ◽  
Aerodynamic Noise ◽  
Noise Generation ◽  
Modeling And Analysis ◽  
Exposure Limit

Aerodynamic noise generated in high speed face milling cutters is usually much higher than the noise exposure limit set by OSHA. Experiments were conducted on two different face milling cutters to understand the aerodynamic noise generation in face milling cutters. It is observed that dipole sources of noise are most important in determining the noise generation in rotating face milling cutters. The aerodynamic noise spectrum consists of discrete tones at the rotational frequency and a broad range of higher frequencies, with the broadband spectrum contributing significantly to overall noise. A mathematical model based on the Ffowcs Williams-Hawkings Equation is used to predict (un-weighted) aerodynamic noise. The noise predicted compares well with the experimental observations. The cutter gullet shape was found to be an important factor in determining broadband noise.

Sign in / Sign up

Export Citation Format

Share Document