Far-field sound radiation of a submerged cylindrical shell at finite depth from the free surface

The vibration response and far-field sound radiation of a semisubmerged, finite cylindrical shell with low-frequency excitation are studied. The solution to this problem can be divided into two steps. The first step is to apply the wave propagation approach to determine the vibration response of the cylindrical shell. In the cylindrical coordinate system, the Flügge shell equations and Laplace equation are used to describe the cylindrical shell and surrounding fluid so that the vibration responses of the shell can be addressed analytically. The fluid free surface effect is taken into account by applying the sine series to force the velocity potential on the free surface to be zero. Furthermore, compared with the FEM (the finite element method), the present method is not only reliable but also effective. In the second step, the far-field sound radiation is solved by the Fourier transform technique and the stationary phase method in accordance with the vibration responses of the shell from the previous step. The boundary element method is applied to validate the reliability of the acoustical radiation calculation. The circumferential directivity of far-field sound pressure is discussed, and it is found that the maximum value of the sound pressure always appears directly under the structure when the driving frequencies are relatively low. Besides, in consideration of simplicity and less computation effort, the present method can be used for the rapid prediction of the vibration and far-field sound pressure of a semisubmerged cylindrical shell with low-frequency excitation.

Download Full-text

Prediction of Far-Field Sound Pressure of a Semisubmerged Cylindrical Shell With Low-Frequency Excitation

Journal of Vibration and Acoustics ◽

10.1115/1.4036209 ◽

2017 ◽

Vol 139 (4) ◽

Cited By ~ 4

Author(s):

T. Y. Li ◽

P. Wang ◽

X. Zhu ◽

J. Yang ◽

W. B. Ye

Keyword(s):

Cylindrical Shell ◽

Free Surface ◽

Sound Pressure ◽

Acoustic Radiation ◽

Phase Method ◽

Far Field ◽

Radiation Model ◽

New Approaches ◽

Modal Coupling ◽

Field Sound

A sound–structure interaction model is established to study the vibroacoustic characteristics of a semisubmerged cylindrical shell using the wave propagation approach (WPA). The fluid free surface effect is taken into account by satisfying the sound pressure release condition. Then, the far-field sound pressure is predicted with shell's vibration response using the stationary phase method. Modal coupling effect arises due to the presence of the fluid free surface. New approaches are proposed to handle this problem, i.e., diagonal coupling acoustic radiation model (DCARM) and column coupling acoustic radiation model (CCARM). New approaches are proved to be able to deal with the modal coupling problem efficiently with a good accuracy at a significantly reduced computational cost. Numerical results also indicate that the sound radiation characteristics of a semisubmerged cylindrical shell are quite different from those from the shell fully submerged in fluid. But the far-field sound pressure of a semisubmerged shell fluctuates around that from the shell ideally submerged in fluid. These new approaches can also be used to study the vibroacoustic problems of cylindrical shells partially coupled with fluid.

Download Full-text

The Vibro-Acoustic Characteristics of the Cylindrical Shell Partially Submerged in the Fluid

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.170-173.2303 ◽

2012 ◽

Vol 170-173 ◽

pp. 2303-2311 ◽

Cited By ~ 6

Author(s):

Wen Bing Ye ◽

Tian Yun Li ◽

Xiang Zhu

Keyword(s):

Cylindrical Shell ◽

Free Surface ◽

Power Flow ◽

Sound Pressure ◽

Harmonic Excitation ◽

Input Power ◽

Far Field ◽

Fluid Coupling ◽

Vibrational Power Flow ◽

Field Sound

The characteristics of the sound radiation and vibrational power flow of the partially submerged cylindrical shell under a harmonic excitation are studied. The approximate acoustic boundary of the free surface is used to solve the fluid domain. The structure-fluid coupling equation is established based on the Flügge and Helmholtz theories. The far-field sound pressure is calculated and compared with that in infinite field. It is found that the far-field sound pressure presents large gap in different immersion status in the presence of the free surface while the results of the input power flow in these cases have less differences.

Download Full-text

Far-field acoustic radiation and vibration of a submerged finite cylindrical shell below the free surface based on energy functional variation principle and stationary phase method

Noise Control Engineering Journal ◽

10.3397/1/376570 ◽

2017 ◽

Vol 65 (6) ◽

pp. 565-576

Author(s):

Wenjie Guo ◽

Tianyun Li ◽

Xiang Zhu

Keyword(s):

Cylindrical Shell ◽

Free Surface ◽

Acoustic Radiation ◽

Energy Functional ◽

Phase Method ◽

Stationary Phase Method ◽

Variation Principle ◽

Far Field ◽

Functional Variation ◽

Finite Cylindrical Shell

Download Full-text

On-axis and far-field sound radiation from resilient flat and dome-shaped radiators

The Journal of the Acoustical Society of America ◽

10.1121/1.3075594 ◽

2009 ◽

Vol 125 (3) ◽

pp. 1444-1455 ◽

Cited By ~ 19

Author(s):

Ronald M. Aarts ◽

Augustus J. E. M. Janssen

Keyword(s):

Sound Radiation ◽

Far Field ◽

Field Sound

Download Full-text

Research on vibration and near-field sound radiation of ring-ribbed cylindrical shell coated deadening and decoupling materials

Journal of Marine Science and Application ◽

10.1007/s11804-007-6022-8 ◽

2007 ◽

Vol 6 (1) ◽

pp. 21-30

Author(s):

Xiong-liang Yao ◽

Qing-jie Liu ◽

Xiu-bo Yu

Keyword(s):

Cylindrical Shell ◽

Near Field ◽

Sound Radiation ◽

Near Field Sound ◽

Field Sound

Download Full-text

Coherence decay and its impact on sound radiation by wavepackets

Journal of Fluid Mechanics ◽

10.1017/jfm.2014.186 ◽

2014 ◽

Vol 748 ◽

pp. 399-415 ◽

Cited By ~ 54

Author(s):

André V. G. Cavalieri ◽

Anurag Agarwal

Keyword(s):

Coherence Function ◽

Sound Radiation ◽

Turbulent Jets ◽

Sufficient Condition ◽

Far Field ◽

Mean Flow ◽

Spectral Densities ◽

Flow Fluctuations ◽

Order Of Magnitude ◽

Field Sound

AbstractWavepackets obtained by a linear stability analysis of the turbulent mean flow were shown in recent works to agree closely with some relevant statistics of turbulent jets, such as power spectral densities and averaged phases of flow fluctuations. However, when such wavepacket models were used to calculate the far-field sound, satisfactory agreement was only obtained for flows that were supersonic relative to the ambient speed of sound; attempts with subsonic flows led to errors of more than an order of magnitude. We investigate here the reasons for such discrepancies by developing the integral solution of the Helmholtz equation in terms of the cross-spectral densities of turbulent quantities. It is shown that agreement of a statistical source, such as would be obtained by the above-mentioned wavepacket models, in averaged amplitudes and phases in the near field is not a sufficient condition for exact agreement of the far-field sound. The sufficient condition is that, in addition to the amplitudes and phases, the statistical source should also match the coherence function of the flow fluctuations. This is exemplified in a model problem, where we show that the effect of coherence decay on sound radiation is more prominent for subsonic convection velocities, and its neglect leads to discrepancies of more than an order of magnitude in the far-field sound. For supersonic flows errors are reduced for the peak noise direction, but for other angles the coherence decay is also seen to have a significant effect. Coherence decay in the model source is seen to lead to similar decays in the coherence of two points in the far acoustic field, these decays being significantly faster for higher Mach numbers. The limitations of linear wavepacket models are illustrated with another simplified problem, showing that superposition of time-periodic solutions can lead to a correlation decay between two points. However, the coherence between any pair of points in such models remains unity, and cannot thus represent the behaviour observed in turbulent flows.

Download Full-text

Multi-channel Active Vibration Isolation for the Control of Underwater Sound Radiation From A Stiffened Cylindrical Structure: A Numerical Study

Journal of Vibration and Acoustics ◽

10.1115/1.4004684 ◽

2011 ◽

Vol 134 (1) ◽

Cited By ~ 2

Author(s):

Huang Xiuchang ◽

Zhang Zhiyi ◽

Zhang Zhenhua ◽

Hua Hongxing

Keyword(s):

Cylindrical Shell ◽

Vibration Isolation ◽

Sound Radiation ◽

Spatial Average ◽

Far Field ◽

Underwater Sound ◽

Cylindrical Structure ◽

Vibration Isolators ◽

Active Vibration ◽

Active Vibration Isolation

Numerical simulation of vibration control of a submerged stiffened cylindrical structure with active vibration isolators is presented. Vibration transmission from vibrating machinery to the cylindrical structure through the active vibration isolators is analyzed by a numerical model synthesized from frequency response functions (FRFs) and impedances. The coupled finite element/boundary element (FE/BE) method is employed to study the vibro-acoustic behavior of the fluid-loaded cylindrical structure. Sound pressure in the far-field is calculated in terms of the pressure and normal acceleration of the outer surface of the cylindrical shell. An adaptive multichannel control based on the filtered-x least mean squares (FxLMS) algorithm is used in the active vibration isolation. Simulation results have demonstrated that suppression of vibration of the four elastic foundations attached to the cylindrical shell will reduce the spatial-average mean-square velocity and the instantaneous radiated power of the cylindrical shell. As a result, suppression of vibration of the foundations leads to attenuation of sound radiation in the far-field induced by the radial displacement dominant mode of the shell. Moreover, vibration suppression is greatly influenced by the strong couplings among control channels. According to these results, it can be concluded that the proposed method is effective in the analysis of underwater sound radiation control of cylindrical structures.

Download Full-text