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

A vortex model of cavity flow

1976 ◽  
Author(s):  
J. HARDIN ◽  
J. MASON
Keyword(s):  
Cavity Flow ◽  
Vortex Model

Cavitating Flow Past a Large Aspect-Ratio Hydrofoil

1961 ◽  
Vol 5 (01) ◽  
pp. 1-8
Author(s):  
E. Cumberbatch
Keyword(s):  
Aspect Ratio ◽  
Cavity Flow ◽  
Horseshoe Vortex ◽  
Cavitating Flow ◽  
Large Aspect Ratio ◽  
Central Section ◽  
Tip Vortices ◽  
Vortex Model ◽  
Flow Past ◽  
Good Comparison

Tip effects on the cavitating flow past a large aspect-ratio lifting hydrofoil are considered. The tip vortices arising from the flow leakage around the tip from the lower to the upper side of the hydrofoil are assumed to cavitate. The flow over the central section of the hydrofoil is taken as two-dimensional cavity flow and hence there is a wide planar cavity there. The separate cavity regions are taken not to coalesce. The flow is represented by a simple horseshoe-vortex model and descriptions of the flow over the central section, near the tip and well downstream, are derived and appropriately matched. The lift on the hydrofoil is then calculated, taking the downwash into account. The lift is seen to be reduced by the tip effects, and shows good comparison with experimental results.

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.

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

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.

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