WISpec_readme
, May. 7, 2022, Houwang Tu
Ph.D candidate of National University of Defense Technology
The program WISpec.m
computes the acoustic field in arbitrary horizontally
stratified media (as shown in Figure 1) using the wavenumber integration model
discretized by the Chebyshev--Tau spectral method. The spectral algorithm is
described in the article (H. Tu, Y. Wang, W. Liu et al., A spectral method for
the depth-separated solution of a wavenumber integration model for horizontally
stratified fluid acoustic waveguides [J], Physics of Fluids, 2023(35), 057127,
https://doi.org/10.1063/5.0150221).
The 'ReadEnvParameter
' function is used to read "input.txt
" file.
User can make changes to "input.txt
" for the desired simulation.
The "input.txt
" file contains the parameters defining the modal
calculation. See the following example:
Example1 ! casename
P ! Src, type of sound source
1 ! Layers of media
20 ! Nl (truncation order of layers, Layers rows)
2 ! kmax (maximum integral interval)
20.0 ! freq (frequency of source)
36.0 ! zs (depth of source)
0.25 ! dz (discrete length in depth direction)
3000.0 ! rmax (receiver ranges(m))
1 ! dr (discrete length in horizontal direction)
40 ! tlmin (minimum value of TL in colorbar)
70 ! tlmax (maximum value of TL in colorbar)
100.0 ! h (bathmetries of ocean)
2 ! n (profiles' points in water column)
0.0 1500.0 1.0 0.0 ! dep c rho alpha
100.0 1500.0 1.0 0.0
A ! Lowerboundary (rigid/free/halfspace lower boundary condition)
100.0 2000.0 2.0 2.0 ! sound speed, density and attenuation of semi-infinite space
The "input.txt
" file include:
-
casename
is the name of current example; -
Src
is the type of sound source, P denotes point source, L denotes line source; -
Layers
is the number of the layers of media; -
Nl
s are the numbers to truncated order of media. Generally speaking, the more complicated the shape of the sound speed profile, the moreNl
s are needed to accurately fit. -
kmax
, the integral interval is [0, kmax]. -
freq
(frequency of sound source, Hz), -
zs
(the depth of source, m), -
dz
(step size in depth direction, m), -
rmax
(the maximum range of horizontal direction, m), -
dr
(horizontal discrete step, m), -
tlmin
andtlmax
are the minmum and maximum value transmission loss, respectively, which used to determine the color range of the output transmission loss graph,tlmin
must less thantlmax
. -
h
s are the bathmetries of ocean of ocean, unit: m. -
n
s are the amount of environmental profile data in medium columns.There is a table of environmental parameter: the units are depth(m), speed(m/s), density(g/cm$^3$) and attenuation (dB/wavelength), with
nw
points in each layer. It is necessary thatdepw(n)=depb(1)
where the density usually has a discontinuity. The first entrydep(1)=0
is the free surface. The last entrydep(n)=H
determines the total thickness of the waveguide. -
Lowerboundary
(User used to specify whether the seabottom boundary condition is perfectly free 'V', perfectly rigid 'R' or semi-infinite space 'A'), The last line is the parameters for the semi-infinite space.
Figure 1. Schematic of arbitrary horizontally stratified marine environment.
The plots resulting from the above dialog are as follows:
Figure 2. Wavenumber spectrum of the waveguide.
Figure 3. A colorful plot of transmission loss, range versus depth.