The following can be repeated as many times as wanted in a single ENVFIL. KRAKEN and KRAKENC will generate a separate MODFIL for each case stopping when it detects an end-of-file.
TITLE
Description:
TITLE: Title of run enclosed in sinqle quotes.
Syntax:
FREQ
Description:
FREQ: Frequency in Hz.
Syntax:
NMEDIA
Description:
NMEDIA: Number of media.
The
problem
is divided into media within which it is assumed
that
the material properties vary smoothly. A new medium
should
be used at fluid/elastic interfaces or at interfaces
where the density changes discontinuously. The number
of
media in the problem is defined excluding the upper
and
lower half-space.
BELLHOP is limited to one medium (NMEDIA=1) and actually ignores this parameter.
Syntax:
TOPOPT
Description:
TOPOPT(1:1): Type of interpolation to be used for the SSP.
'C' for C-linear,
'N' for N2-linear (n the index of refraction),
'S' for cubic Spline,
'Q' for Quadrilatteral 2D SSP (BELLHOP only; reads the SSP from a file)
'A' for Analytic.
The user must
modify
the analytic formulas in ANALYT.FOR then re-compile and link.
If your not sure which option to take, I'd suggest you use 'C'. The 'N' option is virtually identical to 'C'. It's provided to facilitate precise intermodel comparisons with codes that use a certain numerical technique that requires that type of interpolation.
Option
'S' is a little dangerous because splines yield
a poor fit to certain kinds of curves, e.g.
curves with sharp bends. If you insist on
splines, you can fix a bad fit by dividing the water
column into two 'media' at the bend.
Run
PLOTSSP to check that the SSP looks the way you thought
it should. Apart from potential typos, this
will also show up fit-problems.
'V' VACUUM above top
'A' ACOUSTO-ELASTIC half-space.
Requires another line with the halfspace parameters as described
in block (4a).
'R' Perfectly RIGID
'F' Reflection coefficient
from a FILE
These
files for complicated, multi-layered media can be generated using
BOUNCE. (Available in KRAKENC, SCOOTER, and BELLHOP. Not available in
KRAKEN and SPARC.) For a Top Reflection Coefficient, the file should
have the extension '.TRC'. For KRAKEN/KRAKENC this
option
for tabulated reflection coefficients is somewhat
experimental at this time. A
complicated
reflection coefficient may well cause problems
for
the mode-finder. Finally, a reflection coefficient tabulated
only for real angles does not provide a good result for
complex
angles of incidence. This happens when the sediment sound
speed
is less than the water sound speed. In that case, the
modes are
evanescent in the upper part of the water column and
therefore
have a complex angle of incidence.
'S' for Soft-boss Twersky
scatter.
'H' for Hard-boss Twersky scatter.
'T' for Soft-boss Twersky scatter, amplitude only.
'I' for Hard-boss Twersky scatter, amplitude only.
The Twersky scatter
options require
another line as described in block(4b).
Mnemonically, T, I options are one letter after S, H in the alphabet.
Current wisdom is that option T is most appropriate
for ice scatter.
TOPOPT(3:3): Attenuation units.
'N' Nepers/m.
'F' dB/(kmHz)
(F as in Freq.
dependent)
'M' dB/m
(M as in per
Meter)
'W' dB/wavelength (W
as in
per
Wavelength)
'Q' quality factor
'L' Loss parameter (a.k.a. loss tangent)
TOPOPT(4:4): Added volume attenuation.
'T' Thorp attenuation
formula.
If you invoke this option, Thorp attenuation is
added to
the explicitly specified attenuation (ap, as).
TOPOPT(5:5): Altimetry option; Slow/robust root-finder.
'*' Read in a *.ati file
containing the top altimetry. (BELLHOP only)
'.' As in: I want all the
modes and I don't care how long it takes. Period.
'I' Calculate only a single
beam from the specified fan.
The actual beam number is specified after NBEAMS,
under
the section describing the beam fan.
' ' Default: trace all beams
Syntax:
ZT CPT CST RHOT APT AST
Description:
ZT: Depth
(m).
CPT: Top P-wave speed (m/s).
CST: Top S-wave speed (m/s).
RHOT: Top
density (g/cm3).
APT: Top P-wave attenuation. (units
as given by Option(3:3) )
AST: Top S-wave attenuation. ( "
" "
"
" " )
Syntax:
BUMDEN ETA XI
Description:
BUMDEN:
Bump density (ridges/km).
ETA: Principal radius 1
(m).
XI: Principal
radius 2 (m).
This line should only be included when one of the Twersky-scatter options is selected.
Syntax:
NMESH
SIGMA
Z(NSSP)
Z(1) CP(1)
CS(1) RHO(1) AP(1)
AS(1)
Z(2) CP(2)
CS(2) RHO(2) AP(2)
AS(2)
.
.
.
Z(NSSP) CP(NSSP)
CS(NSSP)
RHO(NSSP) AP(NSSP)
AS(NSSP)
Description:
NMESH:
Number of mesh points used in the internal discretization.
The number of mesh points should be about 10 per vertical wavelength in acoustic media. In elastic media, the number needed can vary quite a bit; 20 per wavelength is a reasonable starting point.
The number of mesh points used depends on the initial mesh and the number of times it is refined (doubled). The number of mesh doublings can vary from 1 to 5 depending on the parameter RMAX described below.
If you type 0 for the
number of mesh points, the code will calculated
NMESH automatically.
BELLHOP ignores this parameter as it's not
relevant to its numerical technique.
SIGMA:
RMS roughness at the
interface (ignored by BELLHOP and SPARC)
This
value is used to detect the
last SSP point when reading in the profile that
follows.
Z():
Depth (m).
The surface starts at the
first depth point specified. Thus if you have say, XBT data which
starts at 50 m below the surface, then you'll need to put in some SSP
point at 0 m, otherwise the free-surface would be placed at 50 m giving
erroneous results. The points Z(1) and Z(NSSP) MUST correspond to the
depths of interfaces between media.
CP():
P-wave speed
(m/s).
CS(): S-wave speed
(m/s).
RHO(): Density (g/cm3).
Density
variations within an acoustic medium are
at present ignored.
AP(): P-wave
attenuation (units as given in Block
2)
AS(): S-wave
attenuation ( "
" "
"
" ")
The '/' character signals that the remaining data on the line is the same as in the previous line of SSP data. For the very first line the default or 'previous' line is:
0.0 1500.0 0.0 1.0 0.0 0.0
This block
should be repeated for each subsequent medium.
Only KRAKEN and SCOOTER can use the shear wave
information. SPARC and BELLHOP ignore it. BELLHOP also ignores the
volume attenuation, AP, in the ocean so the Thorpe option above is the
way to provide that.
Syntax:
BOTOPT SIGMA
Description:
BOTOPT(1:1): Type of bottom boundary condition.
'V' VACUUM below bottom.
'A' ACOUSTO-ELASTIC half-space.
Requires another line with
the half-space parameters as described in Block (6a).
'R' Perfectly RIGID.
'F' Reflection
coefficient from a FILE
These
files for complicated, multi-layered media can be generated using
BOUNCE. (Available in KRAKENC, SCOOTER, and BELLHOP. Not available in
KRAKEN and SPARC.) For a Bottom Reflection Coefficient, the file should
have the extension '.BRC'. For KRAKEN/KRAKENC this
option
for tabulated reflection coefficients is somewhat
experimental at this time. A
complicated
reflection coefficient may well cause problems
for
the mode-finder. Finally, a reflection coefficient tabulated
only for real angles does not provide a good result for
complex
angles of incidence. This happens when the sediment sound
speed
is less than the water sound speed. In that case, the
modes are
evanescent in the upper part of the water column and
therefore
have a complex angle of incidence.
'P' Precaculated internal
reflection coefficient from a FILE
(available in KRAKENC and SCOOTER, not KRAKEN).
These
files are generated using BOUNCE.
Option 'A' is generally used for ocean bottom
modeling.
BOTOPT(2:2): '*' read in a *.bty file containing
the bottom bathymetry.
SIGMA: Interfacial roughness (m).
Syntax:
ZB CPB CSB RHOB APB ASB
Description:
ZB: Depth
(m).
CPB: Bottom P-wave speed (m/s).
CSB: Bottom S-wave speed (m/s).
RHOB: Bottom
density (g/cm3).
APB: Bottom P-wave attenuation. (units
as given by BOTOPT(3:3) )
ASB: Bottom S-wave attenuation. ( "
" "
"
" " )
For KRAKEN/KRAKENC this option for tabulated reflection coefficients is somewhat experimental at this time. A complicated reflection coefficient may well cause problems for the mode-finder. Finally, a reflection coefficient tabulated only for real angles does not provide a good result for complex angles of incidence. This happens when the sediment sound speed is less than the water sound speed. In that case, the modes are evanescent in the upper part of the water column and therefore have a complex angle of incidence.