Block II: OAST options

In addition to supporting the SAFARI options described in [4], OAST supports a wide suite of new options.

A

Depth-averaged transmission loss plotted for each of the selected field parameters. The averaging is performed over the specified number of receivers (block VI).

C

Range-depth contour plot for transmission loss. Only allowed for one field parameter at a time.

F

A Filon-FFT is applied to evaluate the wavenumber integrals instead of the default FFP.

G

Rough interfaces are assumed to be characterized by a Goff-Jordan power spectrum rather than the default Gaussian.

H

Horizontal velocity calculated.

I

Hankel transform integrands are plotted for each of the selected field parameters.

J

Complex integration contour. The contour is shifted into the upper halfpane by an offset controlled by the input parameter COFF (Block III).

K

Computes the bulk stress. In elastic media the bulk stress only has contributions from the compressional potential. In fluid media the bulk stress is equal to the negative of the pressure. Therefore for fluids this option yields the same result as option N or R.

L

Linear vertical source array.

N

Normal stress (=-p in fluids) calculated.

P

Plane geometry. The sources will be line-sources instead of point-sources as used in the default cylindrical geometry.

R

Computes the radial normal stress (or for plane geometry).

S

Computes the stress equivalent of the shear potential in elastic media. This is an angle-independent measure, proportional to the shear potential, with no contribution from the compressional potential (in contrast to shear stress on a particular plane). For fluids this option yields zero.

T

Transmission loss plotted as function of range for each of the selected field parameters.

V

Vertical velocity calculated.

Z

Plot of velocity profile.

a

Angular spectra of the integration kernels are plotted. A axis is automatically selected representing the grazing angle ( corresponds to horizontal propagation ). NOTE: The same wavenumber corresponds to different grazing angles in different media!. The vertical axis is selected automatically, representing the angular density (as opposed to the wavenumber density for integrand plots ( option I ).

b

Solves the depth-separated wave equation with the lowermost interface condition expressed in terms of a complex reflection coefficient. The reflection coefficient must be tabulated in a input file input.trc which may either be produced from experimental data or by the reflection coefficient module OASR as described on Page. See also there for the file format. The lower halfspace must be specified as vacuum and the last layer as an isovelocity fluid without sources for this option. Add dummy layer if necessary. Further, the frequency sampling must be consistent. Therefore, if this option is combined with option f , the input file must have cosistent logarithmic sampling. Using OASR this is optained by using option C with the same minimum and maximum frequencies, and number of frequencies. Note: Care should be taken using this option with a complex integration contour, option J . The tabulated reflection coefficient must clearly correspond to the same imaginary wavenumber components for OAST to yield proper results. OASR calculates the reflection coefficient for real horizontal wavenumbers.

c

Contours of integration kernels as function of horizontal wavenumber (abcissa) and receiver depth (ordinate). The horizontal wavenumber axis is selected automatically, whereas the depth axis is plotted according to the parameters given for option C. The contour levels are determined automatically.

d

Source/receiver dynamics. OAST v 1.7 handles the problem of source and receiver moving through the waveguide at the same speed and direction. The velocity projection V onto the line connecting source and receiver must be specified in Block III, as shown in table 3. Since source and receiver are moving at identical speeds there is no Doppler shift, but the Green's function is different from the static one, as described by Schmidt and Kuperman[9].

f

Contours of transmission loss plotted vs frequency and range. Requires NFREQ > 0 (see below). A logarithmic frequency axis is assumed for this option. Requires ZMIN, ZMAX and ZINC to be specified in Block XII (same contour levels as for option C which may be specified simultaneously).

g

Rough interfaces are assumed to be characterized by a Goff-Jordan power spectrum rather than the default Gaussian (Same as G).

l

User defined source array. This new option is similar to option L in the sense that that it introduces a vertical source array of time delayed sources of identical type. However, this option allows the depth, amplitude and delay time to be be specified individually for each source in the array. The source data should be provided in a separate file, input.src, in the format described below in Section 6.1.5.

s

Outputs the mean field discontinuity at a rough interface to the file 'input'.rhs for input to the reverberation model OASS.

t

Solves the depth-separated wave equation with the top interface condition expressed in terms of a complex reflection coefficient. The reflection coefficient must be tabulated in a input file input.trc which may either be produced from experimental data or by the reflection coefficient module OASR as described on Page. See also there for the file format. The upper halfspace must be specified as vacuum and the first layer as an isovelocity fluid without sources for this option. Add dummy layer if necessary. Further, the frequency sampling must be consistent. Therefore, if this option is combined with option f , the input file must have cosistent logarithmic sampling. Using OASR this is optained by using option C with the same minimum and maximum frequencies, and number of frequencies. Note: Care should be taken using this option with a complex integration contour, option J . The tabulated reflection coefficient must clearly correspond to the same imaginary wavenumber components for OAST to yield proper results. OASR calculates the reflection coefficient for real horizontal wavenumbers.

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Number (1-4) specifying the source type (explosive, forces, moment) as described in Section 6.1.5