A mooring restraints library for rigid body motions in OpenFOAM

Documentation: https://hfchen20.gitlab.io/foamMooring/

GitHub mirror: https://github.com/hfchen20/foamMooring

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Overview

• Works for two rigid body motion libraries sixDoFRigidBodyMotion and rigidBodyMotion.
• Mooring models of restraints include MAP++, MoorDyn, Moody, groups of linear springs.
• Most restraints support runtime generation of legacy VTK files (including vtk.series).
• You can compile only part of the library (i.e., certain restraints) if that suits your needs.
• No need to change and re-compile the built-in motion libraries and flow solvers.
• Tested on v2012, v2212, v2306, mostly with overset grid solver overInterDyMFoam.
• Should also work with interFoam (deforming mesh) and other variants waveFoam and olaFlow.
• Even overPimpleDyMFoam ...

{width=400px height=320px} {width=400px height=320px} {width=600px height=320px}

Compile foamMooring

Prerequisites: git, make, CMake, and VTK if USE_VTK=ON when compiling MoorDyn v2. MAP++ may require other dependent libraries, such as lapacke.

• Clone the repo in $WM_PROJECT_USER_DIR.

mkdir -p $WM_PROJECT_USER_DIR 
cd $WM_PROJECT_USER_DIR
git clone https://gitlab.com/hfchen20/foamMooring.git
cd foamMooring 

If there is no interest in the quasi-static mooring model MAP++, specify a branch option, -b dynamic-only, when cloning the repo.

git clone -b dynamic-only https://gitlab.com/hfchen20/foamMooring.git

• Run Allwmake. Upon successful compilation, there should be at least two libraries, libsixDoFMooring.so and librigidBodyMooring.so, in $FOAM_USER_LIBBIN.

./Allwmake

• You can selectively compile part of the library. If there is difficulty in compiling MAP++ and map3R (quasi-static mooring code), you could skip compiling MAP++ in Allwmake and remove/comment out the corresponding entries in the Make files. For files, remove

map3R/mapFoamInterface.C
map3R/map3R.C

For options, remove

-llapacke \
-lmap-1.30.00 \

Actually, a new branch dynamic-only was created for users not interested in the quasi-static mooring model. Specify the branch name when you clone the repo in the first step above.

git clone -b dynamic-only https://gitlab.com/hfchen20/foamMooring.git 

Code structure

How to use (tested on v2012, v2212)

Refer to documentation for more examples.

• Prepare an OpenFOAM case as usual. The floating body motion can be accommodated by either deforming mesh interFoam or overset grid overInterDyMFoam.
• Add in controlDict

libs    (sixDoFMooring); // or (rigidBodyMooring)

• Prepare a mooring input file in case subfolder "Mooring". For example, for sixDoFMooring

  • MoorDyn v1: lines.txt (filename hard-coded)

  • MoorDyn v2: lines_v2.txt

  • Moody: boxWu_exPoint.m

  • MAP++: esflOWC_4lines.map

• Define mooring restraints in constant/dynamicMeshDict

// Example mooring restraints as defined in libsixDoFMooring, add one of
//	moorDynR1 || moorDynR2 || map3R || moodyR 

moorDynR1
{
    sixDoFRigidBodyMotionRestraint moorDynR1;
}

moorDynR2_pt
{
    sixDoFRigidBodyMotionRestraint  moorDynR2;
    couplingMode       "POINT";
    inputFile          "Mooring/lines_v2_point.txt";
    refAttachmentPt
    (
        (-0.1      0.1    -0.077)
        (-0.1     -0.1    -0.077)
        ( 0.1      0.1    -0.077)
        ( 0.1     -0.1    -0.077)
    );
    writeMooringVTK    true;
    vtkPrefix         "mdv2_pt";
    vtkStartTime       0;
    outerCorrector     1;
}

moorDynR2_bd
{
    sixDoFRigidBodyMotionRestraint  moorDynR2;
    couplingMode       "BODY";
    inputFile          "Mooring/lines_v2.txt";
    writeMooringVTK    true;
    vtkPrefix          "mdv2_body";
    vtkStartTime       0;
    outerCorrector     1;
}

map3R
{
    sixDoFRigidBodyMotionRestraint map3R;
    inputFile                     "Mooring/esflOWC_4lines.map";
    summaryFile                   "Mooring/esflOWC_summary.map";
    waterDepth                    0.5;
    refAttachmentPt
    (
        (-0.1      0.1    -0.077)
        (-0.1     -0.1    -0.077)
        ( 0.1      0.1    -0.077)
        ( 0.1     -0.1    -0.077)
    );
    numberOfSegments       20;
    writeMooringVTK        true;
}

moodyR
{
    sixDoFRigidBodyMotionRestraint moodyR;
    inputFile              "Mooring/boxWu_exPoint.m";

    couplingMode           "externalPoint";  // or "externalRigidBody"
    nCouplingDof           6;
    refAttachmentPt
    (
        (-0.1      0.1    -0.077)
        (-0.1     -0.1    -0.077)
        ( 0.1      0.1    -0.077)
        ( 0.1     -0.1    -0.077)
    );
    waveKinematics         false;
    twoD                   true;
}

Main features of mooring models

Visualize mooring lines in Paraview

• Write VTK files 'mooringN.vtk' for mooring lines where N denotes a time sequence number.
• Prepare a vtk.series file 'mooring.vtk.series' to be loaded into Paraview.
• A Python script and example VTK files are provided in the tutorial to post-process MoorDyn output.
• The mooring tension could also be added to the VTK files.
• MoorDyn v2 has a built-in functionality to write XML-based VTK files.

References

• Chen, H., & Hall, M. (2022). CFD simulation of floating body motion with mooring dynamics: Coupling MoorDyn with OpenFOAM, Applied Ocean Research, 124, 103210. https://doi.org/10.1016/j.apor.2022.103210
• Chen, H., Medina, T. A., & Cercos-Pita, J. L. (2024). CFD simulation of multiple moored floating structures using OpenFOAM: An open-access mooring restraints library. Ocean Engineering, 303, 117697. https://doi.org/10.1016/j.oceaneng.2024.117697 (preprint)

Disclaimer

This offering is not approved or endorsed by OpenCFD Limited, producer and distributor of the OpenFOAM software via www.openfoam.com, and owner of the OPENFOAM® and OpenCFD® trade marks. This offering is not approved or endorsed by any software packages mentioned above or their respective owners, and should not be considered as such.

OpenFOAM is a free, open source CFD software released and developed by OpenCFD Ltd since 2004. It has a large user base across most areas of engineering and science, from both commercial and academic organisations. See documentation