ON THE ACOUSTIC RADIATION FIELD OF THE PIEZO-ELECTRIC OSCILLATOR AND THE EFFECT OF VISCOSITY ON TRANSMISSION

1934 ◽  
Vol 11 (2) ◽  
pp. 135-155 ◽  
Author(s):  
Louis V. King
Keyword(s):  
Radiation Field ◽  
Velocity Potential ◽  
Marked Effect ◽  
Acoustic Radiation ◽  
Wave Length ◽  
Practical Importance ◽  
Circular Disc ◽  
Circular Aperture ◽  
Constant Output ◽  
Infinite Integral

The radiation field due to a circular disc oscillating with uniform amplitude in a closely fitting circular aperture surrounded by an infinite rigid flange has been studied in detail, the velocity potential being expressed as an infinite integral involving cylindrical co-ordinates. The procedure adopted may be used to study the effect of viscosity on the characteristics of the radiation field. While having little effect on the field in the neighborhood of an oscillator generating waves in water, the viscosity has a marked effect on the range of distant transmission, which in consequence is appreciably affected by temperature. Of considerable practical importance is the existence of an optimum wave-length for constant output and a given distance of transmission. By means of a simple chart, it is possible to determine the optimum wave-length for a given transmitter when the level of reception for a given range is stated.

ON THE ACOUSTIC RADIATION FIELD OF THE PIEZO-ELECTRIC OSCILLATOR AND THE EFFECT OF VISCOSITY ON TRANSMISSION: PART II

1934 ◽  
Vol 11 (4) ◽  
pp. 484-488 ◽  
Author(s):  
L. V. King
Keyword(s):  
Radiation Field ◽  
Sea Water ◽  
Acoustic Radiation ◽  
Wave Length ◽  
Numerical Data ◽  
Transmission Part ◽  
Coefficient Of Viscosity ◽  
Theoretical Results ◽  
Piezo Electric

Numerical data on the distance of transmission of sound in sea water from a 10-in. piezo-electric oscillator are discussed in the light of theoretical results obtained in a previous paper. It is shown how by the principle of similitude the chart for transmission at optimum wave-length calculated for a 50-watt, 60 cm. oscillator can be used for a transmitter of any given diameter and output. A comparison with some experiments of Boyle's points to the fact that at supersonic frequencies, in the neighborhood of 100,000 cycles, a considerably higher coefficient of viscosity than that obtained by flow methods must be used.

scholarly journals The period of a spherical resonator with a circular aperture

1916 ◽  
Vol 92 (644) ◽  
pp. 549-555 ◽  
Keyword(s):  
Velocity Potential ◽  
Wave Length ◽  
Helmholtz Resonator ◽  
Small Radius ◽  
Normal Velocity ◽  
Circular Aperture ◽  
Spherical Vessel ◽  
Spherical Resonator

In a paper on “The Theory of the Helmholtz Resonator,” Lord Rayleigh has carried the determination of the wave-length of the fundamental aërial vibration in a spherical vessel with a small circular perforation to a second approximation, obtaining the result λ = π√(2S/ a ) . {1-9/10 a /2π c +...}, (1) where c is the radius of the sphere, a the small radius of the aperture, and S the volume of the sphere. To obtain this value he assumes a form for the normal velocity U over the aperture and adjusts it so as to lead to agreement, to a corresponding approximation, in the values of the velocity potential derived therefrom over the aperture inside and outside, so as to provide for the condition of continuity of pressure at the opening. It is the object of this note to carry the result, by a slightly different assumption for U, to a higher approximation.

scholarly journals On the theory of the inertia and diffraction corrections for the Rayleigh disc

1935 ◽  
Vol 153 (878) ◽  
pp. 17-40 ◽  
Keyword(s):  
Wave Front ◽  
Acoustic Radiation ◽  
Stationary Wave ◽  
Negative Sign ◽  
Circular Disc ◽  
Sound Waves ◽  
Velocity Amplitude ◽  
Radiation Fields ◽  
Quartz Fibre

A thin circular disc suspended by a quartz fibre tends to set itself broadside on to the direction of the propagation of incident sound waves, and its use in combination with resonators is well known as a means of measuring relative intensities of acoustic radiation fields. In a progressive or stationary wave in which the velocity amplitude is │ξ│, the average couple on a circular disc of radius a is usually given by the well-known formula L͞ = - ⅔ρ 0 a 3 │ξ│ 2 sin 2α, (1) where ρ 0 is the density of the medium and α is the angle between the direction of propagation of the wave-front and the normal to the disc, while the negative sign indicates that the couple tends to diminish α.

Radiation Loading of a Cylindrical Source in a Fluid-Filled Cylindrical Cavity Embedded Within a Fluid-Saturated Poroelastic Medium

2002 ◽  
Vol 69 (5) ◽  
pp. 675-683 ◽  
Author(s):  
S. M. Hasheminejad ◽  
H. Hosseini
Keyword(s):  
Seismic Waves ◽  
Acoustic Radiation ◽  
Surrounding Medium ◽  
Practical Importance ◽  
Closed Form Solution ◽  
Form Solution ◽  
Radiation Impedance ◽  
Harmonic Field ◽  
Cylindrical Source ◽  
Water Saturated

Radiation loading on a vibrating structure is best described through its radiation impedance. In the present work the modal acoustic radiation impedance load on an infinitely long cylindrical source harmonically excited in circumferentially periodic (axially independent) spatial pattern, while positioned concentrically within a fluid cylinder, which is embedded in a fluid-saturated unbounded elastic porous medium, is computed. This configuration, which is a realistic idealization of an acoustic logging tool suspended in a fluid-filled borehole within a permeable surrounding formation (White, J. E., 1983, Underground Sound Application of Seismic Waves, Elsevier, Amsterdam, Fig. 5.29, p. 183), is of practical importance with a multitude of possible applications in seismo-acoustics and noise control engineering. The formulation utilizes the Biot phenomenological model to represent the behavior of the sound in the porous, fluid-saturated, macroscopically homogeneous and isotropic surrounding medium. Employing the appropriate wave-harmonic field expansions and the pertinent boundary conditions for the given boundary configuration, a closed-form solution in the form of an infinite series is developed and the resistive and reactive components of modal radiation impedances are determined. A numerical example for a cylindrical surface excited in vibrational modes of various order, immersed in a water-filled cavity which is embedded within a water-saturated Ridgefield sandstone environment, is presented and several limiting cases are examined. Effects of porosity, frame stiffness, source size, and the interface permeability condition on the impedance values are presented and discussed.

The Disturbance Due to a Slender Ship Oscillating in Waves in a Fluid of Finite Depth

1966 ◽  
Vol 10 (04) ◽  
pp. 242-252 ◽  
Author(s):  
V. J. Monacella
Keyword(s):  
Ideal Fluid ◽  
Asymptotic Approximation ◽  
Velocity Potential ◽  
Wave Length ◽  
Hydrodynamic Pressure ◽  
Finite Depth ◽  
First Order ◽  
Incident Plane ◽  
Progressive Waves ◽  
Body Potential

The disturbance due to a ship, free to oscillate on the surface of an ideal fluid of finite depth, is studied. The ship is in the presence of oblique, incident, plane progressive waves. Green's theorem is used to represent the velocity potential, and an asymptotic approximation for the first-order slender-body potential valid for all points in the fluid to within a wave length of the ship is found. This is used to determine the hydrodynamic pressure on the bottom of the fluid. Numerical results are presented for the case of a spheroid.

scholarly journals On the problem of the electrified disc

1947 ◽  
Vol 8 (1) ◽  
pp. 14-19 ◽  
Author(s):  
E. T. Copson
Keyword(s):  
External Field ◽  
Gravitational Potential ◽  
Electrostatic Field ◽  
Surface Density ◽  
Wave Length ◽  
Circular Disc ◽  
Sound Waves ◽  
Total Potential ◽  
Induced Charge ◽  
Lord Kelvin

When a perfectly conducting uniform thin circular disc is kept at a potential V0 in an external electrostatic field of potential Φ, electric charge is induced on the surface of the disc; the problem is to find the surface-density σ of this induced charge and its potential V so that the total potential V + Φ has the constant value V0 on the surface of the disc. This problem was first discussed by Green in 1832, and the solution in the case when there is no external field was deduced by Lord Kelvin from the known formula for the gravitational potential of an elliptic homoeoid. The problem is still of interest since similar ideas occur in the theory of diffraction by a circular disc and in the theory of the generation of sound waves by a vibrating disc when the wave-length is large compared with the radius of the disc.

Numerical Analysis of a New-Style Ultrasonic Linear Array

2011 ◽  
Vol 58-60 ◽  
pp. 1043-1048
Author(s):  
Yong Wang ◽  
Quan Lu Li
Keyword(s):  
Numerical Analysis ◽  
Radiation Field ◽  
Acoustic Field ◽  
Linear Array ◽  
Acoustic Radiation ◽  
Acoustic Lens ◽  
Width Direction

In order to reduce the field of the acoustic radiation and improve the efficiency of energy using, a new-style ultrasonic linear array is present, which base on the special structural of the acoustic field produced by the cylindrical acoustic lens. The new-style linear array is composed of numbers of cylindrical acoustic lens, each lens act as an element distributed in a line along the width direction. Define x-direction is the direction of wave propagate. We have studied the acoustic field theoretically and have analyzed it numerically. Found that acoustic field have a better directivity in y-direction and the radiation field is much smaller than the traditional linear array, at the same time the focus ability is appear in the Z-direction if we control the number of element and the distance of center-to-center spacing of each element. This paper is helpful to the change and development of traditional liner array.

scholarly journals Study of SH acoustic radiation field excited by a piezoelectric strip

2005 ◽  
Vol 54 (5) ◽  
pp. 2111
Author(s):  
Zhang Bi-Xing ◽  
Wang Cheng-Hao ◽  
Bostrm Anders
Keyword(s):  
Radiation Field ◽  
Acoustic Radiation ◽  
Piezoelectric Strip
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