# SCOOTER

SCOOTER is a finite element code for computing acoustic fields in range-independent environments. The method is based on direct computation of the spectral integral (reflectivity or FFP method). Pressure is approximated by piecewise-linear elements as are the material properties. (One exception is the density which is approximated by piecewise constant elements).

The SCOOTER package includes two modules:

SCOOTER the main program

FIELDS Produces shade files

The input (.ENV) file is identical to that used by KRAKEN or KRAKENC. The output is a Green's function file (in place of the mode file produced by KRAKEN).

Note that SCOOTER includes the effect of density gradients within media (KRAKEN and KRAKENC do not). Also, interfacial scatter is not treated in SCOOTER.

Files:

Name Description

Input

*.ENV ENVironmental data

*.BRC Bottom Refl. Coef. (optl)

*.TRC Top Refl. Coef. (optl)

*.IRC Internal Refl. Coef. (optl)

Output

*.PRT PRinT file

*.GRN GReeN's function

## EXAMPLE AND DESCRIPTION OF ENV FILE:

'Pekeris problem'

10.0

1

'NVF'

500 0.0 5000.0

0.0 1500.0 /

5000.0 1500.0 /

'A' 0.0

5000.0 2000.0 0.0 2.0 /

1400.0 2000.0

500.0 ! RMax (km)

1 ! NSz

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

1 ! NRz

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

RMax is the maximum range for a receiver. Its real purpose is to set the number of k-space points that will be used in the spectral integral ( deltak = pi / Rmax ). You can get increased accuracy by making Rmax larger than the largest receiver range; however, run time will increase in direct proportion.

Both the source and receiver must lie within the finite-element domain. That is, the capability for placing source or receiver in the homogeneous half-space has not been implemented.

CPU time is roughly independent of the number of receivers but increases linearly with the number of sources. (However, the first source requires about 3 times as much CPU time as subsequent sources, since an LU decomposition is required only for the first source.)

Shade files (complex pressure fields for plots of transmission loss versus range) are obtained by running FIELDS which uses the '.GRN' file as input.