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Author: H. H. Bleich
Publisher:
ISBN:
Category : Differential equations
Languages : en
Pages : 52
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Book Description
A method is presented which permits the determination of the frequencies of vibrations of infinitely long thin cylindrical shells in an acoustic medium. Expressions are obtained for the displacements of the shell and for the pressures in the medium in the case of forced vibrations due to sinusoidally distributed radial forces. The results indicate that there is a low-frequency range, where no radiation takes place, and a high-frequency range where the external force provides energy which is radiated. Resonance occurs in the low-frequency range only; in the high-frequency range it is prevented by the damping due to radiation. Free and forced vibrations of steel shells submerged in water are discussed; with limitations, the theory may be applied approximately to stiffened shells. The method requires only a minor modification to account for the effect of static pressure in the surrounding medium. The treatment of transient problems is also considered. If high-frequency terms occur in the force, or shock effects are wanted within a short time after the application of the force, a treatment using solely modes of vibration of the submerged structure would be incomplete, as additional terms occur in the solution. As an alternative approach, the modes of free vibration of the structure may be used as generalized coordinates which fully describe the response of the structure but leave the medium to be treated, by means of the differential equations for the potential or in any other way desired.
Author: H. H. Bleich
Publisher:
ISBN:
Category : Differential equations
Languages : en
Pages : 52
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Book Description
A method is presented which permits the determination of the frequencies of vibrations of infinitely long thin cylindrical shells in an acoustic medium. Expressions are obtained for the displacements of the shell and for the pressures in the medium in the case of forced vibrations due to sinusoidally distributed radial forces. The results indicate that there is a low-frequency range, where no radiation takes place, and a high-frequency range where the external force provides energy which is radiated. Resonance occurs in the low-frequency range only; in the high-frequency range it is prevented by the damping due to radiation. Free and forced vibrations of steel shells submerged in water are discussed; with limitations, the theory may be applied approximately to stiffened shells. The method requires only a minor modification to account for the effect of static pressure in the surrounding medium. The treatment of transient problems is also considered. If high-frequency terms occur in the force, or shock effects are wanted within a short time after the application of the force, a treatment using solely modes of vibration of the submerged structure would be incomplete, as additional terms occur in the solution. As an alternative approach, the modes of free vibration of the structure may be used as generalized coordinates which fully describe the response of the structure but leave the medium to be treated, by means of the differential equations for the potential or in any other way desired.
Author: Donald J. Butler
Publisher:
ISBN:
Category :
Languages : en
Pages : 72
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Book Description
Author:
Publisher:
ISBN:
Category : Shock (Mechanics)
Languages : en
Pages : 848
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Book Description
Author: Hua Li
Publisher: Elsevier
ISBN: 0080455697
Category : Technology & Engineering
Languages : en
Pages : 283
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Book Description
There are numerous engineering applications for high-speed rotating structures which rotate about their symmetric axes. For example, free-flight sub-munition projectiles rotate at high speeds in order to achieve an aerodynamically-stable flight. This is the first book of its kind to provide a comprehensive and systematic description of rotating shell dynamics. It not only provides the basic derivation of the dynamic governing equations for rotating shells, but documents benchmark results for free vibration, critical speed and parametric resonance. It is written in a simple and clear manner making it accessible both the expert and graduate student. The first monograph to provide a detailed description of rotating shell dynamics Dynamic problems such as free vibration and dynamic stability are examined in detail, for basic shells of revolutions
Author: Arthur W. Leissa
Publisher:
ISBN:
Category : Government publications
Languages : en
Pages : 438
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Book Description
The vibrational characteristics and mechanical properties of shell structures are discussed. The subjects presented are: (1) fundamental equations of thin shell theory, (2) characteristics of thin circular cylindrical shells, (3) complicating effects in circular cylindrical shells, (4) noncircular cylindrical shell properties, (5) characteristics of spherical shells, and (6) solution of three-dimensional equations of motion for cylinders.
Author: Donald Ross
Publisher: Elsevier
ISBN: 1483160467
Category : Science
Languages : en
Pages : 390
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Book Description
Mechanics of Underwater Noise elucidates the basic mechanisms by which noise is generated, transmitted by structures and radiated into the sea. Organized into 10 chapters, this book begins with a description of noise, decibels and levels, significance of spectra, and passive sonar equation. Subsequent chapters discuss sound waves in liquids; acoustic radiation fundamentals; wind-generated ocean ambient noise; vibration isolation and structural damping; and radiation by plate flexural vibrations. Other chapters address cavitation, propeller cavitation noise, radiation by fluctuating-force (dipole) sources, and mechanical noise sources. This book will be helpful as a self-education text and as a reference for workers in the field.
Author: Joshua E. Greenspon
Publisher: CRC Press
ISBN: 1439830940
Category : Science
Languages : en
Pages : 290
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Book Description
From jet engine noise that generates vibrations in the structure of an aircraft, to the sound radiation from the hull of a ship or submarine that makes it identifiable, an understanding of structural acoustics is key in the design process in maritime, automotive, aerospace, and architectural engineering. Building on classic works in the field, Stru
Author:
Publisher:
ISBN:
Category : Mechanics, Applied
Languages : en
Pages : 1006
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Book Description
Author: Stavros Tsakonas
Publisher:
ISBN:
Category : Propellers
Languages : en
Pages : 230
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Book Description
In one instance, an infinitely long elastic beam with circular cross section and in another an in finite elastic plate are immersed in an acoustic fluid parallel to an operating marine propeller. The pressure field generated by the propeller and transmitted and radiated by cylindrical beam or plate is studied by means of Fourier transform techniques. Analytic expressions for the pres sure signals due to the scattering and radiating mechanisms are obtained at large distances from the disturbance and a study is made of their dependence on such important parameters as pro peller clearance, reduced frequencies, number of blades, propeller loading and geometry as well as the elastic properties of the boundary. Further more, closed form expressions of extreme sim plicity are developed for the propeller-induced vibratory force on the cylinder and on the plate. Numerical results are obtained on the assumption of constant loading for a 2- 3- and 4-bladed propeller at various distances and different pro peller clearances. The calculated sound pressures for realistic values of the parameters indicate that an appreciable sound level is obtained through the mechanism of the elastic boundary reaction to the propeller motion. (Author).
Author: J. V. Rattayya
Publisher:
ISBN:
Category : Flutter (Aerodynamics)
Languages : en
Pages : 48
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Book Description
