Free and Forced Vibrations of an Infinitely Long Cylindrical Shell in an Infinite Acoustic Medium

1954 ◽  
Vol 21 (2) ◽  
pp. 167-177
Author(s):  
H. H. Bleich ◽  
M. L. Baron
Keyword(s):  
Surrounding Medium ◽  
Low Frequency ◽  
Free Vibrations ◽  
Forced Vibrations ◽  
Acoustic Medium ◽  
Frequency Range ◽  
Stiffened Shells ◽  
Free And Forced Vibrations ◽  
Water Tables ◽  
Radial Forces

Abstract The paper presents a general method for the treatment of free and forced-vibration problems of infinitely long thin cylindrical shells. Surprisingly simple results are obtained by utilizing the known and tabulated modes of the shell in vacuo as generalized co-ordinates describing the response of the shell. The frequencies of free vibrations of submerged shells are obtained, and the response of the shell and medium to sinusoidally distributed, periodic, radial forces is determined. The results indicate that there is a low-frequency range where no radiation occurs and a high-frequency range where energy is radiated. Free vibration, or resonance in the case of forced vibrations, occurs only in the low-frequency range. The results of the paper may be applied to obtain the response to arbitrarily distributed, periodic, or nonperiodic forces by expanding such forces in Fourier series and/or integrals. The results for free and forced vibrations are discussed in general and for the specific case of steel shells in water. Tables are provided to facilitate numerical computations. With limitations the method is also applicable to ring-stiffened shells, and to the case of a static pressure in the surrounding medium.

On the Accuracy of Dynamic and Acoustic Analysis of Lightweight Panel Structures: A Comparison of ABAQUS and ANSYS

2012 ◽  
Author(s):  
Poul Henning Kirkegaard ◽  
Lars Vabbersgaard Andersen ◽  
Kristoffer Ahrens Dickow
Keyword(s):  
Acoustic Analysis ◽  
Low Frequency ◽  
Coupled Model ◽  
Acoustic Medium ◽  
Building Structures ◽  
Sound Waves ◽  
Frequency Range ◽  
Element Analysis ◽  
Structural Part ◽  
Fully Coupled

During the last couple of years, there has been an increasing focus on the vibro-acoustic performance of built environments due to increasing requirements in building codes regarding impact and airborne sound transmission. Hence, development of efficient and accurate methods for prediction of sound in such buildings is important. In the low-frequency range, prediction of sound and vibration in building structures may be achieved by finite-element analysis (FEA). The aim of this paper is to compare the two commercial codes ABAQUS and ANSYS for FEA of an acoustic-structural coupling in a timber, lightweight panel structure. For this purpose, modal analyses are carried out employing a fully coupled model of sound waves within an acoustic medium and vibrations in the structural part. The study concerns the frequency range 50–250 Hz.

Full‐wave synthetic acoustic logs in radially semiinfinite saturated porous media

Geophysics ◽  
1988 ◽  
Vol 53 (6) ◽  
pp. 807-823 ◽  
Author(s):  
Denis P. Schmitt ◽  
Michel Bouchon ◽  
Guy Bonnet
Keyword(s):  
Time Domain ◽  
Guided Waves ◽  
Surrounding Medium ◽  
Fluid Motion ◽  
Low Frequency ◽  
Homogenization Theory ◽  
Stoneley Wave ◽  
Biot Theory ◽  
Frequency Range ◽  
Types Of Information

The wave field generated by a point source in an axisymmetric fluid‐filled borehole embedded in a saturated porous formation is studied in both the spectral domain and time domain. The formation is modeled following Biot theory modified in accordance with homogenization theory. When the borehole wall is permeable, guided waves can be significantly affected by the permeability of the formation. Whatever the formation, fast or slow, Stoneley‐wave phase velocity and energy decrease and attenuation (in the sense of [Formula: see text]) increases with increasing permeability. These effects are more important in the very low‐frequency range, where Darcy’s law governs the fluid motion and the wave energy at the interface is maximum, than at higher frequencies. The effects increase and persist over a larger frequency range with decreasing viscosity and increasing compressibility of the saturant fluid, with increasing pore‐fluid volume, and with decreasing borehole radius. In contrast, the effects decrease with decreasing stiffness of the formation because of more efficient coupling of the interface wave to the surrounding medium. When present, the first pseudo‐Rayleigh mode also carries useful information. Fluid flow affects only the attenuation of the pseudo‐Rayleigh mode’s Airy phase; an increase in attenuation may be used to detect permeable zones and to infer the saturant fluid properties. However, the most reliable types of information are the formation shear‐wave velocity and attenuation from the low‐frequency part of the mode. In the time domain, all the modes overlap. Any signal processing should then be performed in the frequency domain, where mode spectra are more easily separable. The frequency band of the actual logging tool has to be large enough to ensure significant amplitude for each mode. Finally, the larger the number of receivers and the offset range, the better.

scholarly journals Theoretical and comparative study regarding the Galerkin-Vlasov method use for study the free vibrations of wood flat plate

2010 ◽  
pp. 223-228
Author(s):  
Marius Fetea ◽  
Gabriel Cheregi ◽  
Liana Lustun ◽  
Ildico Smit ◽  
Codruta Lucaci ◽  
...  
Keyword(s):  
19Th Century ◽  
18Th Century ◽  
Free Vibrations ◽  
Forced Vibrations ◽  
Theoretical Studies ◽  
Flat Plates ◽  
Free And Forced Vibrations ◽  
First Results ◽  
Historic Record ◽  
The 19Th Century

As for the historic record of the problem related to the study of flat plates, the first results were out for publishing at the end of the 18th century, the beginning of the 19th century, having Chladni E, Strehlke, Konig, R, Tanaka S, Rayleigh L, Ritz W and later on Gontkevich V, Timoshenko S, Leissa as pioneers. Each of the above mentioned authors have had significant contributions regarding the development of methods in order to solve the plates and establish some rigurous solutions of their differential equations of equilibrium. The making of constructions, machines and different high-perfomance appliances, whose functioning should take place in safety conditions, have required theoretical studies of rich complexity, as well as practical experiments, within which the problem of their free and forced vibrations represent an important category in the respective theme of research.

On Elastic Continua With Hereditary Characteristics

1951 ◽  
Vol 18 (3) ◽  
pp. 273-279
Author(s):  
Enrico Volterra
Keyword(s):  
Equations Of Motion ◽  
Free Vibrations ◽  
Forced Vibrations ◽  
Degree Of Freedom ◽  
Elastic Media ◽  
Stress Strain ◽  
Radial Vibrations ◽  
Damping Characteristics ◽  
Transverse Vibrations ◽  
Free And Forced Vibrations

Abstract In a previous paper (1) the free and forced vibrations of systems of one degree of freedom with hereditary damping characteristics were discussed. In the present paper the classical equations of motion for elastic media are extended on the basis of the general linear stress-strain law involving hereditary damping. These equations are applied to the case of free radial vibrations of a sphere. Furthermore, the free vibrations of strings, the free transverse vibrations of beams, and the free vibrations of rectangular and circular membranes are studied under the assumption of hereditary damping.

Free Vibrations of Fluid-Conveying Cylindrical Shells

1974 ◽  
Vol 96 (2) ◽  
pp. 420-426 ◽  
Author(s):  
S. S. Chen ◽  
G. S. Rosenberg
Keyword(s):  
Potential Flow ◽  
Cylindrical Shells ◽  
Low Frequency ◽  
Free Vibrations ◽  
Frequency Equation ◽  
Frequency Range ◽  
Frequency Spectra ◽  
Flowing Fluid ◽  
Shell Motion ◽  
Conveying Fluid

This paper treats the free vibrations of cylindrical shells conveying fluid. The shell motion is described by the Flu¨gge’s equations, whereas the hydrodynamic forces are described by the linearized potential flow theory. Frequency spectra are presented for symmetric and asymmetric modes and the effects of flow velocity and other parameters are discussed. In the low-frequency range, a modified water-hammer theory and an approximate bending frequency equation including the effect of the flowing fluid are developed.

scholarly journals Microscopic Dynamic Mechanism of Irreversible Thermodynamic Equilibration of Crystals

2021 ◽  
Vol 3 (4) ◽  
pp. 724-730
Author(s):  
A. Yu. Zakharov ◽  
M. A. Zakharov
Keyword(s):  
Initial Conditions ◽  
Stationary Regime ◽  
Irreversible Thermodynamic ◽  
Free Vibrations ◽  
Forced Vibrations ◽  
Dynamic Mechanism ◽  
Harmonic Model ◽  
Free And Forced Vibrations ◽  
Statistical Dynamic ◽  
A Chain

The dynamics of free and forced vibrations of a chain of particles are investigated in a harmonic model taking into account the retardation of interactions between atoms. It is found that the retardation of interactions between particles leads to the non-existence of stationary free vibrations of the crystal lattice. It is shown that in the case of a stable lattice, forced vibrations, regardless of the initial conditions, pass into a stationary regime. A non-statistical dynamic mechanism of the irreversible thermodynamic equilibration is proposed.

scholarly journals Static and Dynamic Behavior of Circular Cylindrical Shell Made of Hyperelastic Arterial Material

2016 ◽  
Vol 83 (5) ◽  
Author(s):  
Ivan D. Breslavsky ◽  
Marco Amabili ◽  
Mathias Legrand
Keyword(s):  
Nonlinear Dynamics ◽  
Cylindrical Shell ◽  
Circular Cylindrical Shell ◽  
Single Mode ◽  
Forced Vibrations ◽  
Dynamic Responses ◽  
Free And Forced Vibrations ◽  
Static Responses ◽  
Radial Forces ◽  
Mode Response

Static and dynamic responses of a circular cylindrical shell made of hyperelastic arterial material are studied. The material is modeled as a combination of Neo-Hookean and Fung materials. Two types of pressure loads are studied—distributed radial forces and deformation-dependent pressure. The static responses of the shell under these two loads differ essentially at moderate strains, while the behavior is similar for small loads. The principal difference is that the axial displacements are much larger for the shell under distributed radial forces, while for actual pressure the shell is stretched both in circumferential and axial directions. Free and forced vibrations around preloaded configurations are analyzed. In both cases, the nonlinearity of the single-mode (driven mode) response of the preloaded shell is quite weak, but a resonant regime with both driven and companion modes active has been found with more complicated nonlinear dynamics.

Evaluation of Special Hearing Aids for Deaf Children

1971 ◽  
Vol 36 (4) ◽  
pp. 527-537 ◽  
Author(s):  
Norman P. Erber
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Hearing Aid ◽  
Low Frequency ◽  
Acoustic Stimulation ◽  
Deaf Children ◽  
Frequency Range ◽  
Frequency Limit ◽  
Unpublished Studies ◽  
Published Research

Two types of special hearing aid have been developed recently to improve the reception of speech by profoundly deaf children. In a different way, each special system provides greater low-frequency acoustic stimulation to deaf ears than does a conventional hearing aid. One of the devices extends the low-frequency limit of amplification; the other shifts high-frequency energy to a lower frequency range. In general, previous evaluations of these special hearing aids have obtained inconsistent or inconclusive results. This paper reviews most of the published research on the use of special hearing aids by deaf children, summarizes several unpublished studies, and suggests a set of guidelines for future evaluations of special and conventional amplification systems.

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