This data record signifies that the following spectra, until the next SPGR data record, form one spectral group.
2 5 7 11 16 21 31
- --- -- ---- ----- ----- -------- --
|X| | |SPGR|XXXXX|XXXXX|XXXXXXXX|
- --- -- ---- ----- ----- -------- --
| | | |
| | | |_(2) No other data is required (I5)
| | |
| | |_(1) Compulsory Data Record Keyword(A4)
| |
| |_Optional User Identifier (A2)
|
|_Compulsory END on last data record in Data Category (A3)
LIMITATIONS
Program applicability:
Aqwa-Line - the SPGR card is recognized, but there can be only one spectral group containing only one spectrum.
Aqwa-Librium - up to 20 spectral groups.
Aqwa-Fer - up to 20 spectral groups.
Aqwa-Drift - only one spectral group is allowed.
Aqwa-Naut - only one spectral group is allowed.
The overall maximum total number of spectra in all groups is 20.
In the following sections the term sub-spectrum is used.
A user-defined 2D (carpet) spectrum is a single spectrum, but it may consist of up to 41 sub-spectra.
A spectrum with a spreading function is modeled in Aqwa with a series of sub-spectra at Gauss integration points, the number of which is defined by the SPDN data record.
A spectrum with cross-swell contains 2 sub-spectra.
A spectral group may contain up to 20 spectra, subject to the overall limit above. Therefore, if a group contains 20 spectra, there can be only one group. The spectra can be any of the available types, i.e. JONSWAP, Pierson-Moskowitz, Gaussian, user-defined or imported using the IWHT data record.
There may be up to 5 IWHT data records, but these must all be in the same spectral group. Within a group they must be listed consecutively and the list terminated with a FINI data record.
A spectral group may contain up to 41 sub-spectra in total.
A spectral group may contain only one definition of wind and/or current.
If there is no wind or current defined in a spectral group, the values will be taken from the last WIND or CURR data record read. This is consistent with behavior in earlier versions of Aqwa.
An example of a spectral group definition is shown below. This group contains a wind spectrum, a current, a JONSWAP spectrum and a user-defined spectrum. It also makes use of both spectrum and group names.
SPGR
SGNM Example of Spectral Group definition
NPDW
WIND 12.000 126.00 13.0
CURR 1.000 30.00
SPDN 20.0
NAME Spectrum 1 - JONSWAP
JONH 0.2 1.5 2.0 1.00000 0.6
SPDN -135.0
NAME Spectrum 2 - simple user-defined spectrum
UDEF 0.100 0.000
UDEF 0.300 2.000
UDEF 0.700 2.000
UDEF 0.900 0.000
FINI
*
SPGR (Next Group begins)