# FIELD

#

The FIELD program uses the modes calculated by KRAKEN and produces a shade file which contains a sequence of snapshots of the acoustic field as a function of range and depth. A snapshot is produced for every source depth specified by the user.

Files:

Name Description

Input

*.FLP FieLd Parameters

*.MOD MODe files

Output

*.PRT PRinT file

*.SHD SHaDe file

## EXAMPLE AND DESCRIPTION OF FLP FILE:

/, ! TITLE

'RA' ! OPT 'X/R', 'C/A'

9999 ! M (number of modes to include)

1 ! NPROF

0.0 ! RPROF(1:NPROF) (km)

501 ! NRr

200.0 220.0 / ! R( 1 : NRr ) (km)

1 ! NSz

500.0 / ! Sz( 1 : NSz ) (m)

1 ! NRz

2500.0 / ! Rz( 1 : NRz ) (m)

1 ! NRro

0.0 / ! Rro( 1 : NRro ) (m)

(1) - TITLE

Syntax:

TITLE

Description:

TITLE: Title to be written to the shade file.

If you type a /, the title is taken from the first mode file.

(2) - OPTIONS

Syntax:

OPTION

Description:

OPTION(1:1): Source type.

'R' point source

(cylindrical (R-Z) coordinates)

'X' line source

(cartesian (X-Z) coordinates)

OPTION(2:2): Selects coupled or adiabatic mode theory.

'C' Coupled mode theory.

'A' Adiabatic mode theory (default).

OPTION(3:3): Selects a source beam pattern

'*' Read in a source beam pattern file.

'O' Omni-directional (default).

OPTION(4:4): Selects coherent or incoherent mode addition

'C' Coherent

'I' Incoherent

For a coupled mode run you ***must*** be sure that the modes are finely sampled throughout the media (excluding the halfspaces if present) so that FIELD can accurately calculate the coupling integrals. This is done by using a large number of receiver depths (NRD) when you do the KRAKEN run. This number should be set to give about 10 points/wavelength.

(3) - NUMBER OF MODES

Syntax:

M

Description:

M: Number of modes to use in the field computation.

If the number of modes specified exceeds the

number computed then the program uses all the

computed modes.

(4) - PROFILE RANGES

Syntax:

NProf RPROF( 1 : NProf )

Description:

NProf: The number of profiles, i.e. ranges where a new set of modes is to be used.

RProf( 1 : NProf ): Ranges (km) of each of these profiles.

For a range independent problem there is only one profile and its range is arbitrary. The modes for the last SSP profile are extended in a range-independent fashion to infinity so that RMax can exceed RProf( NProf ).

*** NOTE: RProf( 1 ) must be 0.0 ***

(6) - SOURCE/RECEIVER LOCATIONS

Syntax:

NRr

R( 1 : NRr )

NSz

Sz( 1 : NSz )

NRz

Rz( 1 : NRz )

NRro

RR( 1 : NRro )

Description:

NRr: Number of receiver ranges.

R(): The receiver ranges (km)

NSz: The number of source depths.

Sz(): The source depths (m).

NRz: The number of receiver depths.

Rz(): The receiver depths (m).

NRro: The number of receiver range-displacements.

Must equal NRz. (YES, IT IS REDUNDANT)

Rro(): The receiver displacements (m).

This vector should be all zeros for a perfectly vertical array.

The field is computed by stepping through the ranges, Rr(1:NR), and adding in the range displacements, Rro() before computing the field on the array. Nonzero values are used to tilt or distort the receiving array, thereby simulating the distortion which occurs on an array deployed in the ocean.

The format of the source info is an integer indicating the number of sources followed by real numbers indicating the depths of each source. The same format is used for receivers. Since this data is read in using list-directed I/O you can type it just about any way you want, e.g. on one line or split onto several lines. Also if your depths are equally spaced then you can type just the first and last depths followed by a '/' and the intermediate depths will be generated automatically.