Effect of a free surface on the far‐field pressure radiated by a point‐excited cylindrical shell

1991 ◽  
Vol 90 (4) ◽  
pp. 2173-2181 ◽  
Author(s):  
Pierre Salaün
Keyword(s):  
Cylindrical Shell ◽  
Free Surface ◽  
Far Field

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

2017 ◽  
Vol 139 (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.

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

2012 ◽  
Vol 170-173 ◽  
pp. 2303-2311 ◽  
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.

scholarly journals An Analytical Solution for the Vibration and Far-Field Sound Radiation Analysis of Finite, Semisubmerged Cylindrical Shells

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Wenjie Guo ◽  
Zhou Yang ◽  
Yueyang Han
Keyword(s):  
Cylindrical Shell ◽  
Free Surface ◽  
Present Method ◽  
Sound Pressure ◽  
Low Frequency ◽  
Sound Radiation ◽  
Far Field ◽  
Vibration Responses ◽  
Frequency Excitation ◽  
Field Sound

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.

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

2014 ◽  
Vol 136 (3) ◽  
pp. 1054-1064 ◽  
Author(s):  
T. Y. Li ◽  
Y. Y. Miao ◽  
W. B. Ye ◽  
X. Zhu ◽  
X. M. Zhu
Keyword(s):  
Cylindrical Shell ◽  
Free Surface ◽  
Sound Radiation ◽  
Finite Depth ◽  
Far Field ◽  
Field Sound

A simple example from flat-ship theory

1988 ◽  
Vol 189 ◽  
pp. 301-310 ◽  
Author(s):  
Susan Cole
Keyword(s):  
Exact Solution ◽  
Free Surface ◽  
Energy Balance ◽  
Aspect Ratio ◽  
Pressure Distribution ◽  
Wave Drag ◽  
Vortical Flow ◽  
Far Field ◽  
Low Aspect Ratio ◽  
Free Surface Waves

This paper describes the induced pressure distribution, free-surface waves, vortical flow and wave drag of an exact solution of low-aspect-ratio flat-ship theory. An energy balance is derived which relates the spray drag, the energy carried away by the far-field waves and the vortical flow to the total wave drag.

scholarly journals Study on the Coupling Frequency of Double-Sided Submerged Ring-Stiffened Cylindrical Shells

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Anbin Yu ◽  
Yinglong Zhao ◽  
Youqian Wang ◽  
Ben Zhang
Keyword(s):  
Cylindrical Shell ◽  
Free Surface ◽  
Hydrostatic Pressure ◽  
Water Immersion ◽  
Theoretical Method ◽  
Coupling Model ◽  
Acoustic Vibration ◽  
Stiffened Cylindrical Shell ◽  
Calculation Results ◽  
Coupling Frequency

Based on the Flügge theory and orthotropic theory, the acoustic vibration coupling model of ring-stiffened cylindrical shell is established by using the wave propagation method and virtual source method. And the effects of water immersion on both sides, free surface, and hydrostatic pressure on the cylindrical shell are considered in the coupling model. Muller three-point iterative method is used to solve the coupling frequency. The calculation results of degradation theory are compared with COMSOL’s calculation results and experimental results, respectively, which verifies the reliability of the theoretical method. Finally, the influence of fluid load, ring rib parameters, boundary conditions, hydrostatic pressure, and free surface on the coupled vibration of ring-stiffened cylindrical shell is analyzed by an example.

Analysis of Lift and Drag on a Surface-Piercing Foil

1993 ◽  
Author(s):  
John C. Kuhn ◽  
Carl A. Scragg
Keyword(s):  
Free Surface ◽  
Aspect Ratio ◽  
Boundary Value Problem ◽  
Wave Field ◽  
Mathematical Problem ◽  
Far Field ◽  
Wave Fields ◽  
Lifting Surfaces ◽  
Lift And Drag ◽  
Reflection Plane

Hydrofoils operating at shallow depths ( e.g. keels and rudders) will be affected by the interactions between the lifting surfaces and the free surface. This problem is approached computationally and experimentally by examining the simple case of a surface-piercing hydrofoil operating at steady forward speeds and small angles of attack. It is shown that there are two contributions to the lift and drag on the foil, one due to the vorticity shed into the wake and another due to the port/starboard asymmetry of the radiated wave field. The mathematical problem is specified as a linearized boundary-value problem to be solved numerically. The two contributions to the lift and drag on the foil are determined independently from far-field momentum integrations. Calculations of the lift and drag on surface-piercing foils with variations in aspect ratio and heel angle are compared to experimental results. Comparisons of the predicted and measured radiated wave fields generated by the foils are also presented. It is found that the efficiency of the foil is reduced by the presence of the free surface and that the use of simple reflection-plane models can lead to significant errors.

Near and Far-Field Evaluations of the Free-Surface Multipole Potential

1989 ◽  
Vol 33 (01) ◽  
pp. 10-15
Author(s):  
Stuart B. Cohen
Keyword(s):  
Free Surface ◽  
Integral Representation ◽  
Infinite Series ◽  
Digital Computer ◽  
Velocity Potential ◽  
Series Representation ◽  
Rapid Evaluation ◽  
Far Field ◽  
Small Field ◽  
Significant Figures

The general mth-order, free-surface, multipole velocity potential is considered and found suitable for arrays of spherical devices requiring interactions between the devices. Expansions into an infinite series representation and an integral representation with finite limits are shown. These expressions can be evaluated by digital computer to any degree of accuracy and are formulated for especially rapid evaluation in certain regions: the series representation for small field distances, and the integral representation for large distances. Tables of the potentials and their Cartesian and radial derivatives are given to eight significant figures. Illustrations of multipoles between m = 0 and m = 4 are shown.

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

2011 ◽  
Vol 134 (1) ◽  
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.

Sign in / Sign up

Export Citation Format

Share Document