Capabilities and route selection

CableDyn deliberately exposes several execution routes over one solver core. A feature can be implemented in the core yet unavailable on a particular route because that caller does not provide the required motion, fluid field, or restart state. Use this page to choose the route before writing a deck. The evidence behind every checked item is recorded in CableDyn verification and validation; rejected combinations fail closed with a named error.

Execution routes

Route	Boundary owner	Best use	Start here
Released CableDyn_driver.exe	deck coordinates, held ends, motionFile, vesselMotion, or vesselRAO	static design, property checkout, prescribed-motion dynamics, waves/current studies	Standalone Windows driver
Source-build cabledyn (build/cabledyn; build\bin\cabledyn.exe with the conda toolchain on Windows)	same deck route as the release driver	source builds, tests, and research automation	Installation
CableDyn-enabled openfast.exe (OpenFAST, maintained by NLR, the National Laboratory of the Rockies, formerly NREL)	OpenFAST platform/body motion and SeaState	full turbine simulations, DLCs, mixed mooring/power-cable systems, FAST.Farm	OpenFAST with CompMooring = 5
Python executable wrapper	a Python process launching the standalone driver	parameter sweeps, managed output, post-processing	Python package
C ABI / in-process Python API	the embedding program	CFD and custom co-simulation with explicit kinematics-in/loads-out ownership	C API reference

Line and constitutive capability

Model	Status	Scope
Linear EI = 0 chain, wire, polyester, nylon	Supported	static and implicit dynamics; taut, semi-taut, and grounded catenary configurations
Composite line	Supported	one line assembled from ordered sections with independent type, length, and mesh density
Finite-EI bending cable	Supported	production cubic-Hermite static/dynamic path for suspended and flat/structured seabed-contact cables in standalone and OpenFAST-coupled use; the uncommon two-moving-end standalone topology uses a separate compatibility solver
Mixed EI = 0 + finite-EI deck	Supported with route limits	a mixed deck of lines between held or coupled points only (no bodies, rods, or Free/Connect points) runs in OpenFAST and standalone as a static or held-end dynamic run, and rejects a standalone motionFile or deck waves; a mixed deck with bodies, rods, or Free/Connect points runs standalone on the multibody march, with moving objects and deck waves/current, but not with a motionFile
Viscoelastic rope (MoorDyn ElasticMod 2/3)	Supported	per-element series-Kelvin state (standard linear solid only when BA_D = 0), including load-dependent dynamic stiffness; EI = 0 lines
Syrope polyester	Supported with limits	single-section taut dynamic line with OWC and two history states; composite, hydro, finite-EI, current, and wave combinations fail closed by name
Torsion of finite-EI lines	Standalone only, with limits	condensed isotropic torsion (uniform torque, quasi-static: no torsional inertia) of a finite-EI line restrained in torsion at both ends (END CONNECTIONS torsion columns, explicit GJ), in statics with a stability check and buckling descent, and in dynamics with turning Rigid6 bodies, vesselMotion/vesselRAO and the motionFile roll column; Torq/Twist channels and range graphs. Stopped by name: coupled OpenFAST and FAST.Farm, the mixed EI = 0 + finite-EI aggregate, rod ends, bodies other than Rigid6, lines with ATTACHMENTS, modal analysis, False alpha_force_blend, and C API object queries (which take EI = 0 decks only). Not modelled: seabed friction against twist, torque–tension coupling, anisotropic sections, self-contact of a loop (see Condensed torsion)
Hockling loops, nonlinear cross-section laws	Not provided	the buckling onset and the post-buckled shape are computed, but a loop that closes on itself is not resolved; the secondary Cosserat path (Solver paths) is not a production route
Discrete attachments (ATTACHMENTS: buoyancy modules, clumps)	Supported	lumped at nodes of a finite-EI cable, standalone and coupled; rejected on the two-moving-end compatibility solver
Modal analysis (nModes)	Standalone only	natural frequencies and mode shapes of each line about its static equilibrium (all EI = 0 lines, or all finite-EI lines on the Hermite route; flat seabed); a deck with torsion is rejected
VIV (compVIV)	Not implemented	use another validated model; CableDyn rejects the request

Loads and environment

Feature	Status	Important ownership rule
Gravity and displaced-volume buoyancy	Supported	SI input; water density may come from the deck or OpenFAST environment
Morison drag, added mass, Froude–Krylov	Supported	line and supported rigid-object fields use the same nodewise fluid contract
Flat seabed contact and friction	Supported	declare WtrDpth, kBot, cBot and optional friction; supported for coupled finite-EI touchdown cables as well as EI = 0 lines
Anisotropic seabed friction	Supported with limits	frictionMuAxial/frictionMuLateral (OrcaFlex axial and normal coefficients), within the friction limits listed in OPTIONS reference and defaults
Structured bathymetry	Supported with limits	mutually exclusive with flat WtrDpth; coupled finite-EI cables query the global surface through their chord frame; see Deck format reference (.dat)
Uniform/profile current	Supported	standalone deck source; coupled runs use explicitly selected host/file sources
Airy and JONSWAP waves	Supported	standalone deck source or OpenFAST SeaState, never an accidental double source
Regular nonlinear (Dean stream-function) waves	Standalone only	deck stream H T dir waves, StreamOrder
ISSC/Pierson-Moskowitz, Torsethaugen and Ochi-Hubble spectra, cos-2s spreading, multiple wave trains	Standalone only	deck waves/wavetrain rows with WaveSpreading; see OPTIONS reference and defaults
Prescribed vessel motion (vesselMotion, vesselRAO)	Standalone only	a 6-DOF vessel record, or the RAO response to the deck waves, moves every Coupled/Vessel point of a line deck; see OPTIONS reference and defaults
Range graphs (r line output flag, RangeStart)	Standalone only	minimum, maximum, and mean along each line over the run; a coupled OpenFAST deck rejects the flag
WaterKin CurrentMod-1 file table	Supported	bit-identical to the equivalent inline depth profile
WaterKin WaveKinMod-1 history	Standalone only	resampled over TMax; caller-driven use fails closed because the aggregate has no self-driven per-step wave refresh
WaterKin WaveKinMod-2 / in-file SEASTATE	Coupled only	consumes the host SeaState through the OpenFAST shell and requires that field to exist

Topology and coupled objects

CableDyn’s native objects are finite-element lines and boundary attachments. POINTS, BODIES, and RODS are MoorDyn-compatible deck records that the driver translates; they are not an alternative discretisation of the line. Supported translations include fixed/coupled/vessel attachments, free or connecting masses and clumps, Point3 buoys, Rigid6 bodies, and coupled rigid rods. In OpenFAST, Coupled/Vessel bodies and rods are platform-borne 6-DOF nodes that return a force and a moment; the C API and Python run free bodies and rods in still water. The coupled body/rod routes carry checkpoint state and SeaState drag, Froude–Krylov, and added mass. Rigid6 also carries the documented hydrostatic restoring terms. Consult Deck format reference (.dat) before using an imported object because unsupported fields fail closed.

OpenFAST coverage

The CompMooring = 5 shell covers normal coupled time-domain stepping with its own dtM, nonzero PtfmInit, correction iterations, SeaState fields, checkpoint/restart, scoped quasi-static dYdu linearisation, line failures, active-tension control for EI = 0 lines, and FAST.Farm shared moorings. Restart and linearisation do not arise under FAST.Farm, which does not call those module operations. Active ServoDyn control of a finite-EI cable remains rejected. See OpenFAST with CompMooring = 5 for setup and Coupling boundary for the interface contract.

How to interpret this page

Supported means the route is implemented and covered by regression tests, not that every conceivable combination is valid. Physical source ownership still matters. When two requested features cannot be separated without double counting—for example a host field whose private current cannot be split from its wave field—CableDyn stops rather than guessing. The fatal message and Troubleshooting identify the conflicting sources.