Wind
Contents
[WIND]
The reference manual in pdf can be found here.
[BODY#]
Each vessel has its own characteristics with regards to wind, that's why a few records are added to the BODY section:
| Keyword | Unit | Description | Options | Version |
|---|---|---|---|---|
| Lpp |
[m] | Length between perpendicular | (compulsory) | aNySIM_V8.0 |
| Beam | [m] | Breadth of body | (compulsory) | aNySIM_V8.0 |
| CoG | [m] | Cog's coordinates | (compulsory) | aNySIM_V8.0 |
| WindFrontArea | [m2] | Surface of front area | (compulsory) | aNySIM_V8.0 |
| WindSideArea | [m2] | Surface of side area | (compulsory) | aNySIM_V8.0 |
| WindCoefFile | [-] | Wind coefficient file | (compulsory) | aNySIM_V8.0 |
[WIND]
| Keyword | Unit | Description | Options | Version |
|---|---|---|---|---|
| WindType | [-] | 3 choices: Constant Spectrum Timetrace |
(compulsory) | aNySIM_V8.0 |
| MeanSpeed | [m/s] | Mean wind speed | (compulsory for constant wind and spectrum) | aNySIM_V8.0 |
| MeanDirection | [deg] | Mean wind direction ('going to' direction in global EF referential) | (compulsory) | aNySIM_V8.0 |
| WindSpeedSpectrum | [-] | 8 choices: Harris API Ochi Wills NPD Davenport UserDef None |
(compulsory for wind-spectrum) | aNySIM_V8.0 |
| WindDirectionSpectrum | [-] | 3 choices: White noise UserDef None |
(optional) | aNySIM_V8.0 |
| WindDirectionStDev | [deg] | White noise parameter | (compulsory for White noise) | aNySIM_V8.0 |
| UserDefSpeedSpectrumFile | [-] | File path and name of wind-speed-spectrum | (compulsory for UserDef) | aNySIM_V8.0 |
| UserDefDirSpectrumFile | [-] | File path and name of wind-direction-spectrum | (compulsory for UserDef direction spectrum) | aNySIM_V8.0 |
| SeedNumberSpeed | [-] | Seed number | (compulsory for any wind-spectrum) | aNySIM_V8.0 |
| SeedNumberDir | [-] | Seed number | (compulsory for any direction spectrum) | aNySIM_V8.0 |
| WindTimeseriesFile | [-] | File path and name of wind-speed-timetrace | (compulsory if WindType is Timetrace) | aNySIM_V8.0 |
| ApplyShielding | [-] | Boolean switch | (optional) | |
| UpstreamBodyNr | [-] | Index of upstream body in shielding model | (compulsory if ApplyShielding is true) | aNySIM_V8.0 |
| DownstreamBodyNr | [-] | Index of downstream body in shielding model | (compulsory if ApplyShielding is true) | aNySIM_V8.0 |
| WindWakeFile | [-] | File path and name of wind-speed-timetrace | (compulsory if ApplyShielding is true) | aNySIM_V8.0 |
[Output]
The following signals can be written in the output files.
| Alias | Index1 | Index2 | Description | Version |
|---|---|---|---|---|
| WindSp | - | - | Absolute wind speed ([m/s]) | aNySIM_V8.0 |
| WindDr | - | - | Absolute wind direction in engineering referential ([deg]) | aNySIM_V8.0 |
| Fwind | iBody | iMode | Forces at cog in the local referential of the body with index iBody (6 modes, [kN],[kN.m]) | aNySIM_V8.0 |
The format of the user supplied files
User supplied wind speed spectrum
The wind speed spectrum file is a free-format file. The first line contains the reference height to which the spectrum applies. The second line gives the units of the frequencies, which are either "Hz" or "rad/s". Next two columns follow, the first column with the wind gust frequencies and the second column with the wind speed spectral densities in (m/s)^2^s. The frequencies need not be equidistant, but must be in increasing order. There is no limit to the number of frequencies. An example is shown below:
ReferenceHeight = 10.0 FrequencyUnits = Hz 0.01 15.0 0.02 12.0 0.03 8.0 0.06 3.0 0.08 1.0 0.10 0.2
User supplied wind direction spectrum
The wind direction spectrum file is a free-format file. The first line contains the reference height to which the spectrum applies. The second line gives the units of the frequencies, which are either "Hz" or "rad/s". Next two columns follow, the first column with the wind gust frequencies and the second column with the wind direction spectral densities in deg2s. The frequencies need not be equidistant, but must be in increasing order. There is no limit to the number of frequencies. An example is shown below:
ReferenceHeight = 10.0 FrequencyUnits = rad/s 0.01 15.0 0.5 0.2
User supplied wind timetraces
The wind timetraces file is a free-format file. The first line contains the reference height to which the timetraces apply. Next three columns follow, the first column with the time in s, the second column with the wind speed in m/s and the third column with the wind direction in deg. The timesteps need not be equidistant, but must be in increasing order. There is no limit to the number of timesteps.
Please note that the aNySIM simulation should not exceed the last timestep of the user supplied timetraces, otherwise the simulation will be stopped premature.
An example is shown below:
ReferenceHeight = 10.0 0 0 180 30 12 175 60 24 170 90 25 160 120 26 150 200 25 150 1200 24 150 1800 12 180
User supplied wind coefficients
The wind coefficients may be given for one or more segments of a body. Dividing a body into several segments is only useful when the wind speed and direction are position dependent, i.e. in case of wind shielding.
The user supplied wind coefficients are defined with respect to xmoment (relative to the centre of the segment, i.e. st. 10 if only one segment is defined), the CL and waterplane area in x,y and z-direction. Anysim will translate the forces and moments of all segments to one Fx, Fy and Mz at CoG.
The number of segments and the number of directions, for which the coefficients are given, are not limited. Because there are no symmetry options the coefficients must be given for all directions, starting at 0 degrees upto 360 degrees. The directions need not be equidistant, but must be in increasing order. The wind module interpolates linearly between directions to determine the coefficients.
The directions are defined in a vessel-fixed, right-handed system of axes: 0 degrees denotes a direction from stern to bow (along the positive X-axis), 90 degrees from starboard to port side (along the positive Y-axis), and so on. The positive rotation is counter-clockwise.
Below an example is given of a file with wind coefficients for a vessel divided into three segments. The format of the file is equal to the format of the SHUTTLE coefficients file, with the exception that for aNySIM three columns are added because aNySIM calculates the wind forces for six degrees of freedom instead of three. Note that a dot (.) has to be used as decimal separator.
Nsegments 3 ReferenceLength 300 ReferenceHeight 10 segment 1 segmentheight 46.75 xmin -150 xmax -50 xmoment 0.0 Ndirections 9 0.0 0.5457 -0.0000 0.0 0.0 0.0 0.0000 45.0 0.3936 0.5168 0.0 0.0 0.0 -0.2104 90.0 0.3918 0.4548 0.0 0.0 0.0 -0.1698 135.0 -0.3196 0.2970 0.0 0.0 0.0 -0.1128 180.0 -0.8704 -0.0036 0.0 0.0 0.0 0.0012 225.0 -0.3198 -0.2964 0.0 0.0 0.0 0.1120 270.0 0.3260 -0.4512 0.0 0.0 0.0 0.1682 315.0 0.3496 -0.5098 0.0 0.0 0.0 0.2066 360.0 0.5457 -0.0000 0.0 0.0 0.0 0.0000 segment 2 segmentheight 21.0 xmin -50. xmax 50. xmoment 0.0 Ndirections 9 0.0 0.0156 0.0000 0.0 0.0 0.0 0.0000 45.0 0.0769 0.1303 0.0 0.0 0.0 0.0006 90.0 -0.0148 0.3033 0.0 0.0 0.0 -0.0034 135.0 -0.0079 0.1428 0.0 0.0 0.0 -0.0017 180.0 -0.0570 0.0071 0.0 0.0 0.0 -0.0005 225.0 -0.0149 -0.1500 0.0 0.0 0.0 0.0009 270.0 0.0412 -0.3134 0.0 0.0 0.0 0.0034 315.0 0.1358 -0.1140 0.0 0.0 0.0 -0.0001 360.0 0.0156 0.0000 0.0 0.0 0.0 0.0000 segment 3 segmentheight 21.0 xmin 50 xmax 150 xmoment 0.0 Ndirections 9 0.0 0.0490 0.0000 0.0 0.0 0.0 0.0000 45.0 -0.0604 0.0547 0.0 0.0 0.0 0.0131 90.0 -0.1928 0.2566 0.0 0.0 0.0 0.0834 135.0 -0.0025 0.3076 0.0 0.0 0.0 0.1136 180.0 -0.0658 0.0008 0.0 0.0 0.0 0.0006 225.0 -0.0061 -0.3138 0.0 0.0 0.0 -0.1151 270.0 -0.1980 -0.2504 0.0 0.0 0.0 -0.0807 315.0 -0.0474 -0.0510 0.0 0.0 0.0 -0.0115 360.0 0.0490 0.0000 0.0 0.0 0.0 0.0000
The reference length is used to scale the segment length, the segment height and segment "xmoment". When wind shielding is applied the reference length of the upstream body is also used to scale the wind wake field.
The reference height is the height above sealevel at which the wind speed is defined. Because in aNySim it is not possible to define a vertical wind profile the program cannot convert the wind speed from one reference height to another. Therefore, the reference height of the coefficients should be equal to the reference height of the user defined wind spectrum or wind timetraces. With a standard wind spectrum, or constant wind speed, it is assumed that the reference height is 10 m.
The segment height is used in the shielding calculation to determine the average pressure. The height is divided into 10 slices. At each slice the pressure is calculated using the X-, Y- and Z-components of the wind wake field and then the average is calculated of the 10 slice pressures.
The segment "xmin" and "xmax" values define the rear and fore ends of the segment relative to the vessel midship. These values are used to calculate the position of the segment in the wind wake field.
The segment "xmoment" is the location at the segment, relative to its centre (station 10 if only one segment is defined), where the yaw moment coefficients are defined. Anysim will translate the yaw-moments of the different segments to one yaw-moment at CoG.
Please note that the sum of the segment lengths S(xmax - xmin) should be equal to the reference length.
