In SWASH a number of variables are used in input and output. The definitions of these variables are mostly conventional.
H_{s} | Significant wave height, in meters, defined as | |
H_{s} = 4 | ||
where E(f ) is the variance density spectrum and f is the frequency. | ||
With respect to output, this quantity is computed as four times the | ||
standard deviation of the surface elevation over the duration [dur] | ||
(see command QUANTITY) in the final stage of the simulation, which | ||
should be long enough to provide statistically reliable wave height. | ||
The simulation period should therefore be long enough to establish | ||
steady-state conditions. | ||
H_{rms} | RMS wave height, in meters, defined as | |
H_{rms} = H_{s} | ||
T_{p} | Peak period, in seconds, defined as inverse of the frequency at which | |
the variance density spectrum is a maximum. | ||
T_{m01} | Mean wave period, in seconds, defined as | |
T_{m01} = | ||
Directional spread | The directional distribution of incident wave energy is given by | |
D() = A cos^{m}() for all frequencies. The power m is related to | ||
the one-sided directional spread as given in Table A.1. | ||
Cr | Courant number defined as follows: | |
Cr = t + | ||
with t the time step, x and y the grid sizes in x - and y -direction, | ||
respectively, and u and v the velocity components in x - and y -direction. | ||
VEL | Current velocity components in x - and y -direction of the problem | |
coordinate system, | except in the case of output with BLOCK command in | |
combination with command FRAME, where x and y relate to the x -axis | ||
and y -axis of the output frame. | ||
MVEL | Mean or time-averaged velocity components in x - and y -direction of | |
the problem coordinate system, except in the case of output with BLOCK | ||
command in combination with command FRAME, where x and y relate | ||
to the x -axis and y -axis of the output frame. Time-averaging is carried | ||
out over the duration [dur] (see command QUANTITY) in the final stage | ||
of the simulation. | ||
WIND | Wind velocity components in x - and y -direction of the problem | |
coordinate sytem, except in the case of output with BLOCK command in | ||
combination with command FRAME, where x and y relate to the x -axis | ||
and y -axis of the output frame. | ||
TIME | Full date-time string. | |
TSEC | Time in seconds with respect to a reference time (see command QUANTITY). | |
Cartesian convention | The direction is the angle between the vector and the positive x -axis, | |
measured counterclockwise. In other words: the direction where the | ||
waves are going to or where the wind is blowing to. | ||
Nautical convention | The direction of the vector from geographic North measured | |
clockwise. In other words: the direction where the waves are coming | ||
from or where the wind is blowing from. | ||
m | directional spread (in ^{o}) |
1. | 37.5 |
2. | 31.5 |
3. | 27.6 |
4. | 24.9 |
5. | 22.9 |
6. | 21.2 |
7. | 19.9 |
8. | 18.8 |
9. | 17.9 |
10. | 17.1 |
15. | 14.2 |
20. | 12.4 |
30. | 10.2 |
40. | 8.9 |
50. | 8.0 |
60. | 7.3 |
70. | 6.8 |
80. | 6.4 |
90. | 6.0 |
100. | 5.7 |
200. | 4.0 |
400. | 2.9 |
800. | 2.0 |