The hydrodynamic data file is composed of a number of sections which represent all of the required input to the ocean wave command:
The comment section contains descriptive text for the model.
* text
where
| * | keyword to signify that this is a comment line |
| text | description of the model |
This section defines some general data for the model.
GENE depth density gravity symxy
where
| GENE | keyword to denote the start of the general model data |
| depth | water depth |
| density | water density |
| gravity | acceleration of gravity |
| symxy |
symmetry integer 0: no symmetry 1: symmetry about x axis 2: symmetry about y axis 3:symmetry about both x and y axes |
The hydrodynamic surface geometry provides information related to the panel definition of the model. Allowance can be made for symmetric models; that is, only one half of the model must be defined for one plane of symmetry, and only a quarter of the model must be defined for double symmetry.
HYDR npan x1(1) y1(1) z1(1) x2(1) y2(1) z2(1) x3(1) y3(1) z3(1) x4(1) y4(1) z4(1) . . x1(npan) y1(npan) z1(npan) x2(1) … x4(npan) y4(npan) z4(npan)
where
| HYDR | keyword to denote start of hydrodynamic panel description |
| npan | number of panels to be defined |
| xk(j) | X coordinate for panel j, node k |
| yk(j) | Y coordinate for panel j, node k |
| zk(j) | Z coordinate for panel j, node k |
The nodes must be arranged in counterclockwise order when viewing the panel from the wetted side. To define a triangular panel, specify the same coordinates for nodes 3 and 4.
Example 13.2: Hydrodynamic Surface Geometry
HYDR 12 15.0 -15.0 0.0 7.5 -15.0 0.0 7.5 -15.0 -7.5 15.0 -15.0 -7.5 15.0 -15.0 -7.5 7.5 -15.0 -7.5 7.5 -15.0 -15.0 15.0 -15.0 -15.0 15.0 -15.0 -15.0 7.5 -15.0 -15.0 7.5 -7.5 -15.0 15.0 -7.5 -15.0 15.0 -7.5 -15.0 7.5 -7.5 -15.0 7.5 0.0 -15.0 15.0 0.0 -15.0 7.5 -15.0 0.0 0.0 -15.0 0.0 0.0 -15.0 -7.5 7.5 -15.0 -7.5 7.5 -15.0 -7.5 0.0 -15.0 -7.5 0.0 -15.0 -15.0 7.5 -15.0 -15.0 7.5 -15.0 -15.0 0.0 -15.0 -15.0 0.0 -7.5 -15.0 7.5 -7.5 -15.0 7.5 -7.5 -15.0 0.0 -7.5 -15.0 0.0 0.0 -15.0 7.5 0.0 -15.0 15.0 -15.0 0.0 15.0 -15.0 -7.5 15.0 -7.5 -7.5 15.0 -7.5 0.0 15.0 -15.0 -7.5 15.0 -15.0 -15.0 15.0 -7.5 -15.0 15.0 -7.5 -7.5 15.0 -7.5 0.0 15.0 -7.5 -7.5 15.0 0.0 -7.5 15.0 0.0 0.0 15.0 -7.5 -7.5 15.0 -7.5 -15.0 15.0 0.0 -15.0 15.0 0.0 -7.5
This section defines the wave periods where hydrodynamic pressures have been computed.
PERD nperd period(1) period(2) ... period(i) period(i+1) period(i+2) ... period(nperd)
where
| PERD | keyword to denote start of wave period data |
| nperd | number of wave periods |
| period(i) | the ith wave period (s) |
The data may be specified in one or more lines until all the periods are entered.
This section defines the wave directions where hydrodynamic pressures have been computed.
DIRN ndirn heading(1) heading(2) ... heading(i) heading(i+1) heading(i+2) ... heading(ndirn)
where
| DIRN | keyword to denote start of wave direction data |
| ndirn | number of wave directions |
| heading(i) | the ith wave
direction (in degrees, between -180 and +180) |
The data may be specified in one or more lines until all the directions are entered.
This section defines the wave directions where hydrodynamic pressures have been computed.
PRES
iperiod iheading region panel magnitude phase
where
| PRES | keyword to denote the start of hydrodynamic pressure values |
iperiod
| period number (position in the period list) |
iheading
| wave direction number (position in the direction list) |
region
|
|
panel
| panel number (must be between 1 and npan) |
magnitude
| pressure amplitude |
phase
| associated phase angle in degrees (with respect to the wave at the center of gravity of the vessel) |
The associated phase angle (phase) determines the
horizontal location of the loading. The magnitude and phase together define the
shape of the harmonic loading curve.
Pressure is positive when acting from the wetted surface towards the inner surface.
If no input pressure is given to a panel at a particular period and direction, the pressure on the panel is assumed to be zero. If more than one set of pressures are defined, their effects are accumulative; that is, the real and imaginary parts of each set are summed together.
Example 13.5: Panel Pressures
PRES 1 1 1 1 25.0 0.0 1 1 1 2 75.0 0.0 1 1 1 3 100.0 0.0 1 1 1 4 100.0 0.0 1 1 1 5 25.0 0.0 1 1 1 6 75.0 0.0
The data in this section describes the line elements used to provide slender body loading.
MORI nmori x1(1) y1(1) z1(1) x2(1) y2(1) z2(1) . . x1(nmori) y1(nmori) z1(nmori) x2(nmori) y2(nmori) z2(nmori)
where
| MORI | keyword to denote start of Morison hydrodynamic element description |
| Nmori | number of Morison elements defined |
| xk(j) | X coordinate for line element j, node k |
| yk(j) | Y coordinate for line element j, node k |
| zk(j) | Z coordinate for line element j, node k |
The data in this section defines the wave kinematics at the nodes of the Morison elements defined above.
WKIN iperiod iheading node element pmag pphs zsmag zsphs vxmag vxphs vymag vyphs vzmag vzphs axmag axphs aymag ayphs azmag azphs
where
| WKIN | keyword to denote start of Morison element wave kinematics definition |
| iperiod | wave period number (position in period list) |
| iheading | wave direction number (position in direction list) |
| node | local node number on Morison element (1 or 2) |
| element | element number referencing the Morison element list |
| pmag | hydrodynamic pressure amplitude |
| pphs | associated phase angle (degrees) |
| zsmag | surface elevation amplitude |
| zsphs | associated phase angle (degrees) |
| vxmag | x velocity amplitude |
| vxphs | associated phase angle (degrees) |
| vymag | y velocity amplitude |
| vyphs | associated phase angle (degrees) |
| vzmag | z velocity amplitude |
| vzphs | associated phase angle (degrees) |
| axmag | x acceleration amplitude |
| axphs | associated phase angle (degrees) |
| aymag | y acceleration amplitude |
| ayphs | associated phase angle (degrees) |
| azmag | z acceleration amplitude |
| azphs | associated phase angle (degrees) |
Note that the data is defined for X, Y and Z in the global directions.
If no input is given to a Morison element at a particular period and direction, the kinematics data on this element are assumed to be zero.
Example 13.7: Morison Element Wave Kinematics Definition
WKIN 1 1 1 134 0.1 15 1.2 15 2.2 15 2.2 15 2.3 15 0.2 15 1.5 15 4.3 15
This section data defines the RAO data. The first line defines the RAO reference position, followed by blocks of data defining RAOs in various periods and directions.
RAOS xr yr zr iperiod iheading xmag xphs ymag yphs zmag zphs rxmag rxphs rymag ryphs rzmag rzphs
where
| RAOS | keyword to denote start of RAO definition |
| xr yr zr | X, Y and Z coordinate of the RAO reference position |
| iperiod | wave period number (position in period list) |
| iheading | wave direction number (position in direction list) |
| xmag | x RAO amplitude |
| xphs | associated phase angle (degrees) |
| ymag | y RAO amplitude |
| yphs | associated phase angle (degrees) |
| zmag | z RAO amplitude |
| zphs | associated phase angle (degrees) |
| rxmag | rx RAO amplitudee (degrees) |
| rxphs | associated phase angle (degrees) |
| rymag | ry RAO amplitude (degrees) |
| ryphs | associated phase angle (degrees) |
| rzmag | rz RAO amplitude (degrees) |
| rzphs | associated phase angle (degrees) |
Example 13.8: RAO Definition
RAOS
0.000000E+00 0.000000E+00 -5.000000E+00
1 1 8.972334E-01 8.999010E+01 6.241512E-08 -1.799247E+02 1.042555E+00 4.346394E-02
7.862426E-09 0.000000E+00 7.524462E-01 -9.000951E+01 2.027182E-07 0.000000E+00
1 2 6.357081E-01 8.999005E+01 6.357080E-01 8.999005E+01 1.042556E+00 4.340762E-02
5.293267E-01 8.999037E+01 5.293267E-01 -9.000961E+01 1.605987E-07 0.000000E+00
This section defines the mass properties of the hydrodynamic model but is currently unused.
MASS xcg ycg zcg Mass(1,1) mass(1,2) .. mass(1,6) . . Mass(6,1) mass(6,2) .. mass(6,6)
where
| MASS | keyword to denote start of mass information |
| xcg ycg zcg | X, Y and Z coordinate of CoG |
| mass(j,k) | mass matrix term |
Example 13.9: Mass Properties
MASS 0.000000E+00 0.000000E+00 -5.000000E+00 1.383750E+07 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 1.383750E+07 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 1.383750E+07 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 7.780000E+08 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 7.780000E+08 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 7.780000E+08