Computing the far field scattered or radiated by objects inside layered fluid media using approximate Green's functions.

A numerically efficient technique is presented for computing the field radiated or scattered from three-dimensional objects embedded within layered acoustic media. The distance between the receivers and the object of interest is supposed to be large compared to the acoustic wavelength. The method requires the pressure and normal particle displacement on the surface of the object or on an arbitrary circumscribing surface, as an input, together with a knowledge of the layered medium Green's functions. The numerical integration of the full wave number spectral representation of the Green's functions is avoided by employing approximate formulas which are available in terms of elementary functions. The pressure and normal particle displacement on the surface of the object of interest, on the other hand, may be known by analytical or numerical means or from experiments. No restrictions are placed on the location of the object, which may lie above, below, or across the interface between the fluid media. The proposed technique is verified through numerical examples, for which the near field pressure and the particle displacement are computed via a finite-element method. The results are compared to validated reference models, which are based on the full wave number spectral integral Green's function.

[1]  I. Karasalo On evaluation of hypersingular integrals over smooth surfaces , 2007 .

[2]  Jean-Pierre Berenger,et al.  A perfectly matched layer for the absorption of electromagnetic waves , 1994 .

[3]  J. R. Fricke Acoustic scattering from elemental Arctic ice features: Numerical modeling results , 1993 .

[4]  Raymond Lim Acoustic scattering by a partially buried three-dimensional elastic obstacle , 1996 .

[5]  Complex-image approximations to the half-space acousto-elastic Green’s function , 2000 .

[6]  H. Schmidt,et al.  Measurements and modeling of acoustic scattering from partially and completely buried spherical shells. , 2002, The Journal of the Acoustical Society of America.

[7]  John A Fawcett,et al.  A method of images for a penetrable acoustic waveguide. , 2003, The Journal of the Acoustical Society of America.

[8]  P. Harris,et al.  A comparison between various boundary integral formulations of the exterior acoustic problem , 1990 .

[9]  Alessandra Tesei,et al.  A computationally efficient finite element model with perfectly matched layers applied to scattering from axially symmetric objects. , 2007, The Journal of the Acoustical Society of America.

[10]  Raymond Lim,et al.  Evaluation of the integrals of target/seabed scattering using the method of complex images. , 2003, The Journal of the Acoustical Society of America.

[11]  Thomas E. Giddings,et al.  A finite element model for acoustic scattering from objects near a fluid-fluid interface , 2006 .

[12]  Ilkka Karasalo Exact Finite Elements for Wave Propagation in Range-Independent Fluid-Solid Media , 1994 .

[13]  Martin Ochmann,et al.  The complex equivalent source method for sound propagation over an impedance plane. , 2004, The Journal of the Acoustical Society of America.

[14]  Harry J Simpson,et al.  Laboratory measurements of sound scattering from a buried sphere above and below the critical angle. , 2003, The Journal of the Acoustical Society of America.

[15]  Henrik Schmidt,et al.  Subcritical scattering from buried elastic shells. , 2006, The Journal of the Acoustical Society of America.

[16]  Raymond Lim,et al.  Scattering by objects buried in underwater sediments: Theory and experiment , 1993 .

[17]  Allan D. Pierce,et al.  Acoustics , 1989 .

[18]  Matthew A. Nobile,et al.  Acoustic propagation over an impedance plane , 1985 .

[19]  Henrik Schmidt,et al.  Virtual Source Approach to Scattering from Partially Buried Elastic Targets , 2005 .

[20]  Gunnar Taraldsen,et al.  The complex image method , 2005 .

[21]  H. Schmidt,et al.  A fast field model for three‐dimensional wave propagation in stratified environments based on the global matrix method , 1985 .