Start-up

PROJect 'name' 'nr'

        'title1'

        'title2'

        'title3'

With this required command the user defines a number of strings to identify the SWAN run (project name e.g., an engineering project) in the print and plot file.

'name'	is the name of the project, at most 16 characters long.
	Default: blanks.
'nr'	is the run identification (to be provided as a character string; e.g. the run
	number) to distinguish this run among other runs for the same project; it is at
	most 4 characters long. It is the only required information in this command.
'title1'	is a string of at most 72 characters provided by the user to appear in the
	output of the program for the user's convenience.
	Default: blanks.
'title2'	same as 'title1'.
'title3'	same as 'title1'.

SET  [level] [nor] [depmin] [maxmes] [maxerr] [grav] [rho] [cdcap]    &

                        |    NAUTical  |
     [inrhog] [hsrerr] <                > [pwtail] [froudmax] [icewind]
                        | -> CARTesian |

With this optional command the user assigns values to various general parameters.

[level]	increase in water level that is constant in space and time can be given with
	this option, [level] is the value of this increase (in m). For a variable water
	level reference is made to the commands INPGRID and READINP.
	Default: [level]=0.
[nor]	direction of North with respect to the $x-$axis (measured counterclockwise);
	default [nor]= 90$^{{\rm o}}$, i.e. $x-$axis of the problem coordinate system
	points East.
	When spherical coordinates are used (see command COORD) the value
	of [nor] may not be modified.
[depmin]	threshold depth (in m). In the computation any positive depth smaller than
	[depmin] is made equal to [depmin].
	Default: [depmin] = 0.05.
[maxmes]	maximum number of error messages (not necessarily the number of errors!)
	during the computation at which the computation is terminated. During the
	computational process messages are written to the print file.
	Default: [maxmes] = 200.
[maxerr]	during pre-processing SWAN checks input data. Depending on the severity
	of the errors encountered during this pre-processing, SWAN does not start
	computations. The user can influence the error level above which SWAN will
	not start computations (at the level indicated the computations will continue).
	The error level [maxerr] is coded as follows:
	1 : warnings,
	2 : errors (possibly automatically repaired or repairable by SWAN),
	3 : severe errors.
	Default: [maxerr] = 1.
[grav]	is the gravitational acceleration (in m/s$^2$).
	Default: [grav] = 9.81.
[rho]	is the water density $\rho$ (in kg/m$^3$).
	Default: [rho] = 1025.
[cdcap]	is the maximum value for the wind drag coefficient. A value of [cdcap] = 99999
	means no cutting off the drag coefficient. A suggestion for this parameter is
	[cdcap] = 2.5$\times$ 10$^{-3}$.
	Default: [cdcap] = 99999.
[inrhog]	to indicate whether the user requires output based on variance or based on true
	energy (see Section 2.5).
	[inrhog] = 0 : output based on variance
	[inrhog] = 1 : output based on true energy
	Default: [inrhog] = 0.
[hsrerr]	the relative difference between the user imposed significant wave height and the
	significant wave height computed by SWAN (anywhere along the computational
	grid boundary) above which a warning will be given. This relative difference
	is the difference normalized with the user provided significant wave height. This
	warning will be given for each boundary grid point where the problem occurs
	(with its $x-$ and $y-$index number of the computational grid). The cause of the
	difference is explained in Section 2.6.3. To supress these warnings (in particular
	for nonstationary computations), set [hsrerr] at a very high value or use
	command OFF BNDCHK.
	Default: [hsrerr] = 0.10.
	ONLY MEANT FOR STRUCTURED GRIDS.
NAUTICAL	indicates that the Nautical convention for wind and wave direction (SWAN input
	and output) will be used instead of the default Cartesian convention.
	For definition, see Section 2.5 or Appendix A.
CARTESIAN	indicates that the Cartesian convention for wind and wave direction (SWAN input
	and output) will be used. For definition, see Section 2.5 or Appendix A.
[pwtail]	power of high frequency tail; defines the shape of the spectral tail above the
	highest prognostic frequency [fhigh] (see command CGRID). The energy density
	is assumed to be proportional to frequency to the power [pwtail].
	Default values depend on formulations of physics:
	command GEN1 : [pwtail] = 5
	command GEN2 : [pwtail] = 5
	command GEN3 KOMEN : [pwtail] = 4
	command GEN3 WESTH : [pwtail] = 4
	command GEN3 JANSSEN : [pwtail] = 5
	If the user wishes to use another value, then this SET command should be
	located in the command file after the GEN1, GEN 2 or GEN3 command
	(these will override the SET command with respect to [pwtail]).
[froudmax]	is the maximum Froude number ($U/\sqrt{gd}$ with $U$ the current and $d$ the water
	depth). The currents taken from a circulation model may mismatch with given
	water depth $d$ in the sense that the Froude number becomes larger than 1.
	For this, the current velocities will be maximized by Froude number times $\sqrt{gd}$.
	Default: [froudmax] = 0.8.
[icewind]	controls the scaling of wind input by open water fraction. Default value of zero
	corresponds to the case where wind input is scaled by the open water fraction.
	If [icewind] = 1 then sea ice does not affect wind input directly. (Though
	there is still indirect effect via the sea ice sink term; see command SICE.)
	Default: [icewind] = 0.

      |-> STATionary    |     |-> TWODimensional |
MODE <                   >   <                    >
      |   NONSTationary |     |   ONEDimensional |

With this optional command the user indicates that the run will be either stationary or nonstationary and one-dimensional (1D-mode) or two-dimensional (2D-mode). Non-stationary means either (see command COMPUTE):

(a)

one nonstationary computations or

(b)

a sequence of stationary computations or

(c)

a mix of (a) and (b).

The default option is STATIONARY TWODIMENSIONAL.

             | -> CARTesian                 |
COORDINATES <                  | -> CCM |    > REPeating
             |    SPHErical   <          >  |
                               |  QC    |

Command to choose between Cartesian and spherical coordinates (see Section 2.5).


A nested SWAN run must use the same coordinate system as the coarse grid SWAN run.

CARTESIAN	all locations and distances are in m. Coordinates are given with respect
	to $x-$ and $y-$axes chosen by the user in the various commands.
SPHERICAL	all coordinates of locations and geographical grid sizes are given in degrees;
	$x$ is longitude with $x=0$ being the Greenwich meridian and $x>0$ is East of
	this meridian; $y$ is latitude with $y>0$ being the Northern hemisphere. Input
	and output grids have to be oriented with their $x-$axis to the East; mesh sizes
	are in degrees. All other distances are in meters.
CCM	defines the projection method in case of spherical coordinates. CCM means
	central conformal Mercator. The horizontal and vertical scales are uniform
	in terms of cm/degree over the area shown. In the centre of the scale is
	identical to that of the conventional Mercator projection (but only at that
	centre). The area in the projection centre is therefore exactly conformal.
QC	the projection method is quasi-cartesian, i.e. the horizontal and vertical scales
	are equal to one another in terms of cm/degree.
REPEATING	this option is only for academic cases. It means that wave energy leaving at one
	end of the domain (in computational $x-$direction) enter at the other side; it is
	as if the wave field repeats itself in $x-$direction with the length of the domain
	in $x-$direction.
	This option cannot be used in combination with computation of set-up (see
	command SETUP). This option is available only with regular grids.

Note that spherical coordinates can also be used for relatively small areas, say 10 or 20 km horizontal dimension. This may be useful if one obtains the boundary conditions by nesting in an oceanic model which is naturally formulated in spherical coordinates.


Note that in case of spherical coordinates regular grids must always be oriented E-W, N-S, i.e. [alpc]=0, [alpinp]=0, [alpfr]=0 (see commands CGRID, INPUT GRID and FRAME, respectively).