CableDyn 0.2.0

CableDyn 0.2.0 extends the OpenFAST coupling to finite-EI cable control and torsion. It also makes tension-only lines robust through slack and snap events, and recovers finite-EI node results from nodal equilibrium. Several static-solve failures are fixed.

Added

• Active tensioning (CONTROL) of finite-EI cables in OpenFAST, alone or with EI = 0 lines.
• Torsion of finite-EI lines in coupled runs: OpenFAST (CompMooring = 5) and FAST.Farm.
• Rods: Pinned, CoupledPinned and VesselPinned rods in coupled OpenFAST runs.
• Sub-stepping of tension-only (EI = 0) lines through fast segment rotation and slack-to-taut snaps, on by default (ei0_substeps auto|off).
• Static seabed friction toward the as-laid position (staticsFriction asLaid, with layAzimuth and asLaidTension), as in OrcaFlex. The default stays none.
• Seabed contact for Free/Connect points and Point3 buoys: a heavy clump no longer sinks through the seabed.
• Anchor uplift channels AnchFz<L>, AnchFH<L> and TDP<L>Grd.
• C ABI 1 minor extension 2 for hosts that drive Coupled points (for example CFD solvers), with matching Python methods.
• New diagnostics that change no results:
  • a run audit of EI = 0 lines;
  • notes for out-of-plane instability, seabed folds, excessive static strain and coarse sections;
  • a warning for nodes outside the SeaState grid.

Changed

• Finite-EI node results: node tension, curvature and bend moment are recovered from nodal equilibrium. On the lazy-wave example the largest tension error falls from 1552 N to 60 N. OutputRecovery element restores the previous definitions.
• EI = 0 time stepping uses a generalised-α force blend, which removes non-physical tension spikes of lines that go slack. Tension statistics of the shipped examples change by at most 0.23 % (mean) and 0.9 % (maximum). False alpha_force_blend selects the former scheme.
• Active tensioning of EI = 0 lines follows MoorDyn-F through length ramps: fairlead tensions within 0.13 %, where they were up to 6.3 % off.
• dtM default in OpenFAST: a deck without dtM solves every glue step (dtM = DT), so the mooring loads reach the platform without delay.
• Local mesh refinement: finite-EI statics refine the mesh only where needed instead of as a whole. A 462-element lazy wave now solves in 0.33 s instead of 10.0 s. Decks that do not refine are unchanged.
• Faster runs for multi-train wave kinematics, cables clamped to bodies or rods, and EI = 0 decks.

Fixed

• Static solves on creased or rough gridded bathymetry, 3D finite-EI solves on coarse meshes, and lines with discrete buoyancy modules in a cross current on a frictional seabed.
• Node channels of a refined finite-EI line now read the deck node named.
• Anchor tension of a laid cable no longer jumps when the line moves out of its plane.
• Rods and Rigid6 bodies: explicit sub-stepping accounts for seabed contact and free-surface crossing, and seabed friction is applied implicitly.
• Error messages are no longer truncated, and they name the cause and workaround.

Known issues

• In OpenFAST, a deck dtM larger than DT holds the loads between CableDyn's steps, so they reach the platform about dtM/2 late. The lag matters for stiff (taut or tension-leg) moorings and for tension statistics; see the note on the manual's OpenFAST page.

CableDyn is developed independently at Inha University and is not affiliated with the EPSRC-funded University of Edinburgh research project of the same name.

The full list is in CHANGELOG.md. The build and test record is in validation/RELEASE_0_2_0.md. The v0.2.0 tag is annotated, not signed.

Assets

Asset	Contents	SHA-256
CableDyn_driver.exe	Standalone solver for Windows x64 (static, no runtime DLLs)	3eb0727e9a329f155de8aad2dd68ba280985b35a2c9482236930ee007ddbcc89
openfast.exe	OpenFAST v5.0.0 with CableDyn as CompMooring = 5	1ba18e46d4b00e7c5340534add6d6c179b8e3e2dd9645b553fcc9035dece77f9
cabledyn-0.2.0-py3-none-any.whl	Python package	8bc843121685e6a9e0af877765f6d1d0a9e7de47c6ab0c5361a2f644eeb0ac73
cabledyn-0.2.0.tar.gz	Python source distribution	b1034bcd4fff0e690f9635121807f0f41693c16be0de1caf9af4426af127dc7b
SHA256SUMS.txt	Checksums of the four files above

CableDyn builds on OpenFAST (NLR, formerly NREL) and reads MoorDyn-format decks thanks to the open format of MoorDyn (Hall et al.). We thank both communities.