scholarly journals Unsteady simulation of tonal noise from isolated centrifugal fan

2020 ◽  
Author(s):  
Martin Ottersten ◽  
Huadong Yao ◽  
Lars Davidson
Keyword(s):  
Experimental Data ◽  
Centrifugal Fan ◽  
Acoustic Analogy ◽  
Tonal Noise ◽  
Aerodynamic Properties ◽  
Trailing Edges ◽  
Recirculating Flows ◽  
Unsteady Simulation ◽  
Inlet Duct

In this study, an isolated centrifugal fan is investigated for the aerodynamic and acoustic performances usingRANS and URANS simulations. The noise is predicted by coupling the URANS and the Ffowcs Williams andHawkings acoustic analogy. The aerodynamic properties obtained from RANS and URANS are consistentwith the experimental data. The magnitudes of the tonal noise at the blade passing frequencies are wellpredicted. Recirculating flows, which are responsible for reducing the fan efficiency and increasing the noisegeneration, are observed between the shroud and the blade trailing edges. It is found that the recirculatingflows are associated with the gap between the shroud and the inlet duct.

Aeroacoustic Study of Tonal Noise Generated by Axial Flow Fans

Volume 1 ◽  
2004 ◽  
Author(s):  
T. Belamri ◽  
G. Wang
Keyword(s):  
Experimental Data ◽  
Axial Flow ◽  
Acoustic Analogy ◽  
Noise Levels ◽  
Tonal Noise ◽  
Torque Distribution ◽  
Axial Fans ◽  
Main Input ◽  
Radial Thrust ◽  
Thrust And Torque

SPLNoise is an aeroacoustic program developed to predict tonal noise generated by low speed axial fans. It is based on a generalization of the acoustic analogy of Lowson. The main input to the program are the radial thrust and torque distribution along the blade. This radial distribution is obtained from a CFD calculation. An automatic link to CFX commercial CFD code was made. Noise testing was performed in the anechoic and reverberant room at the Trane Company. Comparison between predicted noise levels and experimental data is very satisfactory.

An Investigation Into Acoustics and Vibraton of CPAP Devices: Numerical Prediction of Centrifugal Fan Acoustics and Vibration

2013 ◽  
Author(s):  
Xuan-Tung Vuong ◽  
A. M. Al-Jumaily ◽  
Robert Paxton
Keyword(s):  
Numerical Study ◽  
Centrifugal Fan ◽  
Acoustic Analogy ◽  
Flow Induced Vibration ◽  
Upper Airways ◽  
Sound Sources ◽  
Human Interface ◽  
Obstructive Sleep ◽  
Unsteady Simulation ◽  
Cpap Devices

Continuous Positive Air Pressure (CPAP) devices are used to generate pressurized airflow to relieve upper airways and allow Obstructive Sleep Apnea (OSA) patients to breathe comfortably and easily. The airflow path in these devices consists of several components including but is not limited to inlet and outlet ducts, a centrifugal fan, a humidifier and a human interface. These components contribute significantly to the noise generated by the airflow. This research paper present a numerical study of a centrifugal fan performed with commercial ANSYS software package to predict the sound and vibration produced by the centrifugal fan. The methodologies are following: first, the unsteady flow field is computed using the CFD model to obtain aerodynamic quantities and sound sources. Then, the finite element method (FEM) is used to predict the flow-induced vibration using the predicted aerodynamic quantities. Finally, the Ffowcs-William and Hawkings’s (FW-H) acoustic analogy is used to predict the acoustic pressure at the far-field using the sound sources from the unsteady simulation.

Suppression of tonal noise in a centrifugal fan using guide vanes

2015 ◽  
Vol 357 ◽  
pp. 95-106 ◽  
Author(s):  
Kishokanna Paramasivam ◽  
Srithar Rajoo ◽  
Alessandro Romagnoli
Keyword(s):  
Centrifugal Fan ◽  
Tonal Noise ◽  
Guide Vanes

Numerical and Experimental Investigation of the Reynolds Number and Reduced Frequency Effects on Low-Pressure Turbine Airfoils

2021 ◽  
Vol 143 (2) ◽  
Author(s):  
M. Bolinches-Gisbert ◽  
David Cadrecha Robles ◽  
Roque Corral ◽  
Fernando Gisbert
Keyword(s):  
Experimental Data ◽  
Numerical Data ◽  
Low Pressure ◽  
Reconstruction Method ◽  
Low Speed ◽  
Low Pressure Turbine ◽  
Reduced Frequency ◽  
Aerodynamic Properties ◽  
Numerical Solver ◽  
Turbine Airfoils

Abstract This article compares experimental and numerical data for a low-speed high-lift low pressure turbine (LPT) cascade under unsteady flow conditions. Three Reynolds numbers representative of LPTs have been tested, namely, 5 × 104, 105, and 2 × 105; at two reduced frequencies, fr = 0.5 and 1, also representative of LPTs. The experimental data were obtained at the low-speed linear cascade wind tunnel at the Polytechnic University of Madrid using hot wire, Laser Doppler Velocimetry (LDV), and pressure tappings. The numerical solver employs a sixth-order compact scheme based on the flux reconstruction method for spatial discretization and a fourth-order Runge–Kutta method to march in time. The longest case ran 550 h on 40 GPUs to reach a statistically periodic state. Pressure coefficients around the profile, boundary layer profiles and exit cross section distributions of velocity, pressure loss defect, shear Reynolds stress, and angle are compared against high-quality experimental data. Cascade loss and exit angle have also been compared against the experimental data. Very good agreement between experimental and numerical data is seen. The results demonstrate the suitability of the present methodology to predict the aerodynamic properties of unsteady flows around LPT linear cascades accurately.

scholarly journals Bioinspired aerofoil adaptations: the next steps for theoretical models

2019 ◽  
Vol 377 (2159) ◽  
pp. 20190070 ◽  
Author(s):  
Lorna J. Ayton
Keyword(s):  
Experimental Data ◽  
Theoretical Models ◽  
Theoretical Modelling ◽  
Experimental Measurements ◽  
Far Field ◽  
Acoustic Analogy ◽  
Trailing Edge ◽  
Trailing Edge Noise ◽  
Theoretical Predictions ◽  
Field Noise

The extended introduction in this paper reviews the theoretical modelling of leading- and trailing-edge noise, various bioinspired aerofoil adaptations to both the leading and trailing edges of blades, and how these adaptations aid in the reduction of aerofoil–turbulence interaction noise. Attention is given to the agreement between current theoretical predictions and experimental measurements, in particular, for turbulent interactions at the trailing edge of an aerofoil. Where there is a poor agreement between theoretical models and experimental data the features neglected from the theoretical models are discussed. Notably, it is known that theoretical predictions for porous trailing-edge adaptations do not agree well with experimental measurements. Previous works propose the reason for this: theoretical models do not account for surface roughness due to the porous material and thus omit a key noise source. The remainder of this paper, therefore, presents an analytical model, based upon the acoustic analogy, to predict the far-field noise due to a rough surface at the trailing edge of an aerofoil. Unlike previous roughness noise models which focus on roughness over an infinite wall, the model presented here includes diffraction by a sharp edge. The new results are seen to be in better agreement with experimental data than previous models which neglect diffraction by an edge. This new model could then be used to improve theoretical predictions for far-field noise generated by turbulent interactions with a (rough) porous trailing edge. This article is part of the theme issue ‘Frontiers of aeroacoustics research: theory, computation and experiment’.

A Numerical Study of the Blade Passing Frequency Noise of a Centrifugal Fan

2012 ◽  
Author(s):  
Jian-Cheng Cai ◽  
Da-Tong Qi ◽  
Yong-Hai Zhang
Keyword(s):  
Pressure Fluctuation ◽  
Sound Radiation ◽  
Aerodynamic Noise ◽  
Sound Power ◽  
Centrifugal Fan ◽  
Structural Noise ◽  
Tonal Noise ◽  
Fan Noise ◽  
Blade Passing Frequency ◽  
Dipole Sources

Tonal noise constitutes the major part of the overall fan noise, especially the blade passing frequency (BPF) noise which is generally the most dominant component. This paper studies the BPF tonal noise of a centrifugal fan, including the blade noise, casing aerodynamic noise, and casing structural noise caused by the flow-induced casing vibration. Firstly, generation mechanism and propagation process of fan noise were discussed and the measured spectra of fan noise and casing vibration were presented. Secondly, a fully 3-D transient simulation of the internal flow field of the centrifugal fan was carried out by the computational fluid dynamics (CFD) approach. The results revealed that the flow interactions between the impeller and the volute casing caused periodic pressure fluctuations on the solid walls of the impeller and casing. This pressure fluctuation induces aerodynamic noise radiation as dipole sources, as well as structural vibration as force excitations. Thirdly, using the acoustic analogy theory, the aeroacoustic dipole sources on the casing and blade surface were extracted. The BPF casing and blade aerodynamic sound radiation were solved by the boundary element method (BEM) taking into account the scattering effect of the casing structure. Finally, the casing structural noise was studied. The casing forced vibration and sound radiation under the excitation of BPF pressure fluctuation were calculated by finite element method (FEM) and BEM, respectively. The result indicates that at the studied flow rate, the sound power levels of the casing aerodynamic noise, blade aerodynamic noise and casing structural noise are 103 dB, 91 dB and 79 dB with the reference sound power of 1×10−12 W, respectively.

scholarly journals Numerical study of a control scheme on flow-induced cavity noise

2019 ◽  
Vol 283 ◽  
pp. 09002
Author(s):  
Lulu Liu ◽  
Jin Liu ◽  
Shijin Lyu
Keyword(s):  
Experimental Data ◽  
Cavity Length ◽  
Numerical Study ◽  
Numerical Procedure ◽  
Acoustic Analogy ◽  
Cavity Depth ◽  
Eddy Simulation ◽  
Control Scheme ◽  
Large Eddy ◽  
Flow Induced Noise

A numerical procedure for flow induced cavity noise is established in the paper. The procedure is based on large eddy simulation and FW-H acoustic analogy. The computational scheme is validated by comparing with experimental data. The change of flow induced noise along with cavity length, cavity depth and velocity is studied. A noise control scheme, which includes upright grille and oblique grille, is designed for reducing the flow-induced cavity noise. It turns out that the oblique grille shows superiority in the reduction of cavity noise by modifying the flow structure of the sheat layer.

Experimental determination of the tonal noise sources in a centrifugal fan

2006 ◽  
Vol 295 (3-5) ◽  
pp. 781-796 ◽  
Author(s):  
Sandra Velarde-Suárez ◽  
Rafael Ballesteros-Tajadura ◽  
Juan Pablo Hurtado-Cruz ◽  
Carlos Santolaria-Morros
Keyword(s):  
Experimental Determination ◽  
Centrifugal Fan ◽  
Tonal Noise ◽  
Noise Sources

Computational Noise Prediction of a Centrifugal Fan

2007 ◽  
Author(s):  
Esra Sorguven ◽  
Yilmaz Dogan ◽  
Faruk Bayraktar ◽  
Ergin Arslan
Keyword(s):  
Pressure Fluctuations ◽  
Flow Simulation ◽  
Sound Intensity ◽  
Centrifugal Fan ◽  
Acoustic Analogy ◽  
Noise Emission ◽  
Band Frequency ◽  
Eddy Simulation ◽  
Acoustic Sources ◽  
Dependent Flow

In this study, computational aeroacoustics methods are employed to analyze the flow and the noise emission in a centrifugal fan. Unsteady flow inside the centrifugal fan is predicted with large eddy simulation. Acoustic sources are computed based on the results of the time-dependent flow simulation. The turbulent pressure fluctuations on the blades and on the volute of the fan are used as the source terms in the acoustic analogy of Ffowcs Williams and Hawkings. Propagation, diffraction and scattering of the acoustic sources inside the volute are computed with the boundary element method. Numerically obtained sound pressure level distribution in narrow band frequency spectrum is compared with experimental measurements at certain microphone points. The numerical and experimental sound intensity maps are also compared to validate the numerical prediction of directivity. Computational results agree well with the experimental data and provide an insight of the noise emission mechanisms.

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