The radiating near field of a circular normal transducer of arbitrary apodization on an elastic half-space

1999 ◽  
Vol 106 (3) ◽  
pp. 1237-1246 ◽  
Author(s):  
Dmitri Gridin
Keyword(s):  
Half Space ◽  
Near Field ◽  
Elastic Half Space ◽  
Normal Transducer

Scattering by a surface inhomogeneity on an elastic half-space, with application to fluid-structure interaction noise

1990 ◽  
Vol 429 (1876) ◽  
pp. 203-226 ◽  
Keyword(s):  
Turbulent Flow ◽  
Half Space ◽  
Near Field ◽  
Elastic Solid ◽  
Viscous Sublayer ◽  
Elastic Half Space ◽  
Diffraction Radiation ◽  
Frequency Spectra ◽  
Low Mach Number ◽  
Surface Inhomogeneity

A harmonic point source is situated in fluid bounded by a nominally plane interface with an elastic half-space. The source is close to a small protrusion of the elastic medium into the fluid, and it is required to determine the interaction (‘diffraction’) radiation, i. e. the acoustic, elastic-body and surface (Scholte) waves produced by the scattering of the near field of the source by the protrusion. The solution of this canonical problem is applied to the prediction of acoustic and structural noise generated by low Mach number turbulent flow over an inhomogeneity on the boundary of an elastic solid. Estimates are presented of the frequency spectra of the power delivered to the various wave modes and their dependence on the elastic properties of the solid, and a comparison is made with empirical predictions of excitation of the same modes in the absence of the inhomogeneity. The scattered radiation can be significant even when the surface inhomogeneity does not penetrate beyond the viscous sublayer into the turbulent flow.

Steady-state response of an elastic half-space to a moving dislocation of finite width

1983 ◽  
Vol 73 (1) ◽  
pp. 1-22
Author(s):  
J. Enrique Luco ◽  
John G. Anderson
Keyword(s):  
Half Space ◽  
Near Field ◽  
Three Dimensional ◽  
Elastic Half Space ◽  
Numerical Results ◽  
Finite Width ◽  
Slip Vector ◽  
State Response ◽  
Three Dimensional Models ◽  
Fault Length

abstract An analytical method to evaluate the transient response on the surface of an elastic half-space for a kinematic dislocation over an infinitely long fault of finite width and arbitrary dip is presented. The model includes finite rupture velocities in the direction of both the strike and dip of the fault. In this sense, it differs from previous two- and three-dimensional models which typically assume one of these velocities to be infinite. In addition to the effects of the free boundary, the model considers a slip vector in an arbitrary direction. The assumptions of infinite fault length and uniform rupture velocities account for the relative simplicity of the solution which is invariant to an observer moving along the strike of the fault with a speed equal to the rupture velocity. These assumptions limit the applicability of the solution to near-field locations far from the ends of realistic faults. A limited set of numerical results illustrating the types of pulse shapes obtained by use of this model, and, some tests to validate the derivation and the numerical results are presented.

The efficiency of application of virtual cross-sections method and hypotheses MELS in problems of wave signal propagation in elastic waveguides with rough surfaces

2016 ◽  
pp. 3564-3575 ◽  
Author(s):  
Ara Sergey Avetisyan
Keyword(s):  
Half Space ◽  
Cross Sections ◽  
Classical Method ◽  
Signal Propagation ◽  
Elastic Half Space ◽  
Layered Systems ◽  
Surface Layers ◽  
Inhomogeneous Surface ◽  
Wave Signal ◽  
The Impact

The efficiency of virtual cross sections method and MELS (Magneto Elastic Layered Systems) hypotheses application is shown on model problem about distribution of wave field in thin surface layers of waveguide when plane wave signal is propagating in it. The impact of surface non-smoothness on characteristics of propagation of high-frequency horizontally polarized wave signal in isotropic elastic half-space is studied. It is shown that the non-smoothness leads to strong distortion of the wave signal over the waveguide thickness and along wave signal propagation direction as well.  Numerical comparative analysis of change in amplitude and phase characteristics of obtained wave fields against roughness of weakly inhomogeneous surface of homogeneous elastic half-space surface is done by classical method and by proposed approach for different kind of non-smoothness.

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