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Home > User Interface > Results Processing > General Post-Processing > Mooring Lines Characteristic Curves

Mooring lines characteristic curves

The Mooring file post-processing tab allows you to request the FE engine to carry out series of automated static analyses required to derive characteristic curve for mooring lines, i.e. horizontal tension at line ends against horizontal distance between anchor and fairlead.

These characteristic curves may then be used to perform further dynamic analyses of mooring systems with the lines only modelled through their characteristic curve, as per standard mooring analysis software. This approach neglects all inertia and drag effects on the lines and is therefore generally termed quasi-static or quasi-dynamic approach. It significantly speeds up the calculation compared to fully dynamic analysis and enable covering a large range of environmental conditions and getting the low frequency motion response at limited calculation effort.

Each characteristic mooring curve may be requested from the Mooring file tab using the following parameters:

  • Line: Select the mooring line for which you want to extract the characteristic mooring curve. you may select several lines in different rows so that the mooring file will include sets of characteristic mooring curve for several lines.

  • dZ_min (m): This is the minimum range value applicable to the vertical excursion of the floater with respect to its nominal static position. This value must be negative and large enough to cover all possible negative vertical positions of the floater that might be encountered within a quasi-static mooring analysis.

  • Z_max (m): This is the maximum range value applicable to the vertical excursion of the floater with respect to its nominal static position. This value must be positive and large enough to cover all possible positive vertical positions of the floater that might be encountered within a quasi-static mooring analysis.

  • NBZ: This is the total number of vertical excursions of the floater used to cover the range from dZ_min to dZ_max. Typical values are from 5 to 9. Large values improve the accuracy but would increase the calculation time.

  • dX_min (m): This is the minimum range value applicable to the horizontal excursion of the floater with respect to its nominal static position. This value must be negative and large enough to cover all possible negative offsets of the floater that might be encountered within a quasi-static mooring analysis. (where negative means that the horizontal distance between the ends of the line is decreased compared to the static nominal condition).

  • dX_max (m): This is the maximum range value applicable to the horizontal excursion of the floater with respect to its nominal static position. This value must be positive and large enough to cover all possible positive offsets of the floater that might be encountered within a quasi-static mooring analysis. (where positive means that the horizontal distance between the ends of the line is increased compared to the static nominal condition).

  • NBX: This is the total number of horizontal excursions of the floater used to cover the range from dX_min to dX_max. Typical values are about 100. Large values improve the accuracy but would increase the calculation time.

  • Horizontal distance: Defaults to zero. This is an initial horizontal floater offset that could be considered as a starting point. Positive (resp. negative) values would increase (resp. decrease) the initial horizontal distance between both ends of the line. You must use "0" so as to consider the range of positive and negative horizontal offsets will start from the nominal position of the floater.

  • DIODORE structure: This value must be an integer that serves to identify the line ID number in the mooring file. Set the value to "1" if you request a set of characteristic mooring files for a single line.

Thanks to their special formatting, mooring files can then be read by DIODORE mooring analysis software. These files can be used as input to DIODORE when defining a mooring quasi-static analysis.

All mooring files can also be further read by DEEPLINES to perform low frequency quasi-static mooring analyses. The path to these files must be input within the *MOORLINE keyword for this purpose.

Note

this tab is available only when defining Predefined results within a given analysis. The reason is that the Mooring file is generated by DeepLines solver during the computation instead of the GUI.

The characteristic curves are derived by the FE engine and saved into a text- based file which is located in the analysis directory (i.e. nest to other results files that are generated by the FE engine). The name of the file is made of the following character strings : "Analysis Name"+"_F64.dat".

The format of the file listing the characteristic curves and which is generated by the FE engine is presented below :

The files starts with the number of lines for which the characteristic mooring curves are derived. A file may include a single set of characteristic mooring curves (i.e. with the number of lines is 1) or several sets of characteristics mooring curves (i.e. with the number of lines larger than 1).

The file is then made of one or several groups of data. The number of groups of data equals the number of lines for which the characteristic mooring curves are derived.

Every groups of data have similar format, as follows:

  • First row: DIODORE group identification number. This allows identification of the line.

  • Second row: Number of vertical positions considered for the floater excursion (NB_Z), followed by the vertical distance between both ends of the line.

  • These 2 rows are followed by NB_X rows where NB_X is the number of horizontal positions considered for the floater excursion. Each of these rows include 7 columns, as detailed below:

    • Column #1: Horizontal distance between both ends of the line

    • Column #2: Horizontal tension (N) at End_1

    • Column #3: Absolute tension (N) at End_1

    • Column #4: Horizontal tension (N) at End_2

    • Column "5: Absolute tension (N) at End_2

    • Column #6: Either "-1" or "1" depending on the orientation of the line at End_1. "-1" indicates that the tension is oriented downwards and "1" indicates that the tension is directed upwards.

    • Column "7: Either "-1" or "1" depending on the orientation of the line at End_2. "-1" indicates that the tension is oriented downwards and "1" indicates that the tension is directed upwards.

An example of file is shown below:

  1
  1    5
  51    1312.72900
  0.160891E+04  0.737366E+06  0.141900E+07  0.847119E+06  0.851999E+06    -1 1
  0.161091E+04  0.750110E+06  0.143378E+07  0.848504E+06  0.853298E+06    -1 1
  0.161291E+04  0.762977E+06  0.144868E+07  0.856034E+06  0.860844E+06    -1 1
  0.161491E+04  0.776308E+06  0.146415E+07  0.858428E+06  0.863140E+06    -1 1
  0.161691E+04  0.789738E+06  0.147970E+07  0.862439E+06  0.867188E+06    -1 1
  0.161891E+04  0.803622E+06  0.149581E+07  0.870382E+06  0.875205E+06    -1 1
  0.162091E+04  0.817685E+06  0.151211E+07  0.874156E+06  0.878876E+06    -1 1
  0.162291E+04  0.832245E+06  0.152901E+07  0.880325E+06  0.885075E+06    -1 1
  0.162491E+04  0.846858E+06  0.154594E+07  0.882728E+06  0.887374E+06    -1 1
  0.162691E+04  0.862016E+06  0.156353E+07  0.888259E+06  0.893007E+06    -1 1
  0.162891E+04  0.877309E+06  0.158124E+07  0.892181E+06  0.896814E+06    -1 1
  0.163091E+04  0.893020E+06  0.159945E+07  0.899919E+06  0.904654E+06    -1 1
  0.163291E+04  0.909090E+06  0.161808E+07  0.907378E+06  0.911977E+06    -1 1
  0.163491E+04  0.925360E+06  0.163692E+07  0.918205E+06  0.922646E+06    -1 1
  0.163691E+04  0.942165E+06  0.165639E+07  0.936198E+06  0.940720E+06    -1 1
  0.163891E+04  0.959120E+06  0.167601E+07  0.956859E+06  0.961396E+06    -1 1
  0.164091E+04  0.976961E+06  0.169671E+07  0.976961E+06  0.981413E+06    -1 1
  0.164291E+04  0.994961E+06  0.171756E+07  0.994961E+06  0.100058E+07    -1 1
  0.164491E+04  0.101388E+07  0.173954E+07  0.101388E+07  0.102088E+07    -1 1
  0.164691E+04  0.103382E+07  0.176276E+07  0.103382E+07  0.104241E+07    -1 1
  0.164891E+04  0.105488E+07  0.178735E+07  0.105488E+07  0.106529E+07    -1 1
  0.165091E+04  0.107716E+07  0.181345E+07  0.107716E+07  0.108965E+07    -1 1
  0.165291E+04  0.110079E+07  0.184121E+07  0.110079E+07  0.111564E+07    -1 1
  0.165491E+04  0.112591E+07  0.187079E+07  0.112591E+07  0.114344E+07    -1 1
  0.165691E+04  0.115269E+07  0.190242E+07  0.115269E+07  0.117325E+07    -1 1
  0.165891E+04  0.118130E+07  0.193631E+07  0.118130E+07  0.120529E+07    -1 1
  0.166091E+04  0.121198E+07  0.197274E+07  0.121198E+07  0.123985E+07    -1 1
  0.166291E+04  0.124496E+07  0.201203E+07  0.124496E+07  0.127722E+07    -1 1
  0.166491E+04  0.128054E+07  0.205454E+07  0.128054E+07  0.131778E+07    -1 1
  0.166691E+04  0.131908E+07  0.210070E+07  0.131908E+07  0.136196E+07    -1 1
  0.166891E+04  0.136099E+07  0.215105E+07  0.136099E+07  0.141027E+07    -1 1
  0.167091E+04  0.140672E+07  0.220622E+07  0.140675E+07  0.146333E+07    -1 1
  0.167291E+04  0.145696E+07  0.226683E+07  0.145696E+07  0.152187E+07    -1 1
  0.167491E+04  0.151237E+07  0.233397E+07  0.151232E+07  0.158679E+07    -1 1
  0.167691E+04  0.157371E+07  0.240848E+07  0.157371E+07  0.165916E+07    -1 1
  0.167891E+04  0.164218E+07  0.249190E+07  0.164218E+07  0.174031E+07    -1 1
  0.168091E+04  0.171902E+07  0.258577E+07  0.171902E+07  0.183186E+07    -1 1
  0.168291E+04  0.180582E+07  0.269209E+07  0.180582E+07  0.193581E+07    -1 1
  0.168491E+04  0.190452E+07  0.281331E+07  0.190452E+07  0.205461E+07    -1 1
  0.168691E+04  0.201750E+07  0.295242E+07  0.201750E+07  0.219126E+07    -1 1
  0.168891E+04  0.214762E+07  0.311303E+07  0.214762E+07  0.234939E+07    -1 1
  0.169091E+04  0.229827E+07  0.329940E+07  0.229827E+07  0.253326E+07    -1 1
  0.169291E+04  0.247325E+07  0.351635E+07  0.247325E+07  0.274772E+07    -1 1
  0.169491E+04  0.267662E+07  0.376899E+07  0.267662E+07  0.299791E+07    -1 1
  0.169691E+04  0.291221E+07  0.406217E+07  0.291221E+07  0.328874E+07    -1 1
  0.169891E+04  0.318305E+07  0.439971E+07  0.318305E+07  0.362407E+07    -1 1
  0.170091E+04  0.349069E+07  0.478357E+07  0.349064E+07  0.400583E+07    -1 1
  0.170291E+04  0.383410E+07  0.521295E+07  0.383450E+07  0.443347E+07    -1 1
  0.170491E+04  0.421210E+07  0.568490E+07  0.421219E+07  0.490387E+07    -1 1
  0.170691E+04  0.461985E+07  0.619452E+07  0.461987E+07  0.541219E+07    -1 1
  0.170891E+04  0.505300E+07  0.673603E+07  0.505300E+07  0.595263E+07    -1 1
      51    1317.72900
  0.160891E+04  0.761203E+06  0.145018E+07  0.862638E+06  0.867468E+06    -1 1
  0.161091E+04  0.774448E+06  0.146558E+07  0.862156E+06  0.866851E+06    -1 1
  0.161291E+04  0.787748E+06  0.148101E+07  0.871026E+06  0.875789E+06    -1 1
  0.161491E+04  0.801562E+06  0.149707E+07  0.872517E+06  0.877185E+06    -1 1
  0.161691E+04  0.815464E+06  0.151320E+07  0.880162E+06  0.884853E+06    -1 1
  0.161891E+04  0.829829E+06  0.152989E+07  0.880911E+06  0.885503E+06    -1 1
  0.162091E+04  0.844386E+06  0.154679E+07  0.887543E+06  0.892230E+06    -1 1
  0.162291E+04  0.859311E+06  0.156412E+07  0.889735E+06  0.894311E+06    -1 1
  0.162491E+04  0.874570E+06  0.158184E+07  0.895899E+06  0.900515E+06    -1 1
  0.162691E+04  0.890053E+06  0.159981E+07  0.905971E+06  0.910678E+06    -1 1
  0.162891E+04  0.906055E+06  0.161840E+07  0.913886E+06  0.918457E+06    -1 1
  0.163091E+04  0.922098E+06  0.163699E+07  0.924238E+06  0.928655E+06    -1 1
  0.163291E+04  0.938669E+06  0.165621E+07  0.938854E+06  0.943374E+06    -1 1
  0.163491E+04  0.955556E+06  0.167579E+07  0.955556E+06  0.959991E+06    -1 1
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