CableDyn 0.4.0

CableDyn 0.4.0 adds full torsion of finite-EI lines with torque–tension coupling, OpenFAST linearisation with the line dynamics (as MoorDyn-F's), cross-flow VIV, bend stiffeners, and finite-EI cables between two moving ends, in OpenFAST, FAST.Farm and the C API. On the example decks it is 6 % faster than 0.3.0.

Added

• Full torsion of finite-EI lines: a twist angle at every node in the dynamics, with the polar inertia Irn and torsional damping, so torque travels along the line as a torsional wave. Lines free to twist at one end, lines hung from a Fixed rod end (I-tube, J-tube), CONTROL, ATTACHMENTS and modal analysis all take torsion. Torsional modes match the continuum to 2.6e-4 on the first.
• Torque–tension coupling of armoured cables and wire ropes (GJ|K) in statics, dynamics, linearisation and the tensile audits; GJ|0 gives the uncoupled cable bit for bit.
• OpenFAST linearisation with line states, as MoorDyn-F's: on the UMaine chains the reduced stiffness matches MoorDyn-F to 0.1 % and the lowest nine line modes to 0.3 %. The release openfast.exe (single precision) linearises from CableDyn's double-precision loads.
• Section-frame curvature channels CurvX<L>N<J>/CurvY<L>N<J> for the fatigue of an armour wire or conductor; the axes follow the twist.
• Cross-flow VIV (the Thorsen et al. model of MoorDyn v2, LINE TYPES Cl, dF, cF) on EI = 0 lines and finite-EI cables, standalone and coupled, with the LINES output flag V. Lock-in follows MoorDyn-F to two to three digits.
• Bend stiffeners (STIFFENERS): a clamped hang-off follows the planar elastica to 0.2 % of the root moment and OrcaFlex 11.6d's curvature to 0.8 %.
• Finite-EI lines with two moving ends (a cable shared by two floaters, a FAST.Farm shared line), standalone, in OpenFAST, FAST.Farm and the C API, and between two objects on the multibody march.
• CoupledPinned/VesselPinned bodies in OpenFAST; active line control of Syrope, viscoelastic and torsion-restrained lines; composite Syrope lines.
• MoorDyn-C Currents 2 and 5 (time-varying and gridded), identical to MoorDyn-C v2.7.1 at 739 points and times; deck currents, prescribed motion, torsion and TURBINES rows on the mixed EI = 0 + finite-EI deck.
• C API host rotations (ABI 1.3: CableDyn_InitDeckRotating, CableDyn_UpdateRotations, CableDyn_GetCoupledMoments; Python init_deck_rotating).

Changed

• Coupled OpenFAST runs start from the equilibrium in SeaState's steady current (CurrMod 1) instead of the still-water shape.
• A coupled finite-EI cable steps to the deck's dynamic_solver tolerance instead of a fixed 5e-3, which gave wrong tensions; the routes now agree to 5e-8 of the peak tension.
• A finite-EI cable pinned to a light moving object is coupled implicitly (the explicit coupling diverged).
• Waves: WvHiCOff (default 0.5 Hz) cuts an elevation record's components; irregular seas are 20 to 33 % faster, WaveKinMod 1 decks two to four times.
• Intel ifx builds use /fp:precise and automatic local variables (results change at round-off). The macOS wheel needs macOS 15 or newer on Apple silicon.

Fixed

• Thread safety of the Intel builds: concurrent handles crashed, and CableDyn_Close paused the OpenMP runtime of the whole process.
• Static starts that failed or depended on round-off: a cable with End A on the seabed, a lazy wave restrained in torsion in current (any pretwist, every BLAS kernel), torsion between two bodies, neutral, weightless and straight lines, pinned and attachment-carrying cables.
• Physics: an EI = 0 line above the surface on a deck without a seabed was modelled fully submerged (13 % light in air); the anchor force on a sloped seabed; the static start in a sheared current; modal analysis with end connections and attachments.
• OpenFAST: restarts with a finite-EI cable continue bit for bit; Free and pinned objects start from their solved acceleration; tiny channel values no longer print as asterisks.
• Stack overflows of non-static ifx builds and of MinGW FAST.Farm.exe; misleading messages; output files that could overwrite an input deck or another study case.

Upgrading

• OpenFAST checkpoints written by 0.3.0 for finite-EI lines restrained in torsion do not reload.
• Decks with torsion need the section's real polar inertia Irn (the column was unused).
• Results change beyond round-off on decks with torsion, pinned cables on bodies, coupled finite-EI cables, coupled runs in a SeaState current, rotated TURBINES, elevation records with components above WvHiCOff, and EI = 0 lines above the surface without a seabed.

Assets

Asset	Contents	SHA-256
CableDyn_driver.exe	Standalone solver for Windows x64 with AVX2 (static, no runtime DLLs)	3d3a91c53c57f616cb39780fb72d97f817b68c90cb50dc9ad9bbc8dd90f30f2a
openfast.exe	OpenFAST v5.0.0 with CableDyn as CompMooring = 5, Windows x64 with AVX2	ce2069ddc1ee88f823c9aaa1f99c156f9a2dce685c2a6ca2efd3900c3d6e928d
cabledyn-0.4.0-py3-none-any.whl	Python package	b97aacbb708d79b5d1e17f963100ced29140824fb7b48f00adcc20bee1c161b1
cabledyn-0.4.0.tar.gz	Python source distribution	dc604a85188ec69cb739d0a9357cccd84e4bce7336c54bf915234234d8e9279b
SHA256SUMS.txt	Checksums of the four files above

The platform wheels with the native library and driver are on PyPI. The v0.4.0 tag is annotated, not signed.

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.

The build and test record is in validation/RELEASE_0_4_0.md; the full list of changes is in CHANGELOG.md.