Glossary

Offshore mooring/cable and solver terms as CableDyn uses them. Conventions (frames, signs, tension) are defined precisely in Conventions.

added mass: The inertial reaction of the surrounding fluid to line acceleration (Ca coefficients).
anchor: The fixed point where a mooring line terminates on the seabed (End B).
boundary attachment: The native object at a line end: an anchor, fairlead, connector, clump, float, vessel, or rigid body. A MoorDyn-style POINTS row is a deck record that translates to one of these; it is not a CableDyn finite-element node.
buoyancy module: Discrete floats clamped to a cable to make a section net-buoyant; in a deck, a net-buoyant line type (or the EQUIVALENT BUOYANCY block).
catenary: The equilibrium shape of a heavy line hanging under gravity with no bending stiffness — the EI = 0 path’s geometry and the analytical static seed.
clump weight: A discrete mass on a mooring line (a Point3 body or a point with Mass/Vol) that shapes the catenary and adds restoring.
compatibility object: A POINTS, BODIES, or RODS record of the MoorDyn deck layout. These records are translated into line boundary objects or rigid bodies; their MoorDyn node identity is not part of the CableDyn line mesh.
CompMooring = 5: The setting in the .fst file of OpenFAST (maintained by NLR, the National Laboratory of the Rockies, formerly NREL) that selects CableDyn as the mooring/cable module (stock MoorDyn is = 3). See Coupling: OpenFAST and CFD.
Cosserat rod: The secondary finite-EI element with SO(3) rotation DOFs; not part of the validated product. See Solver paths.
coupling boundary: The single kinematics-in / loads-out interface every caller uses; the reason one solver core serves the driver, OpenFAST, and CFD identically. See Coupling boundary.
cubic-Hermite element: CableDyn’s finite-EI (EI > 0) bending element: position + material tangent per node, \(C^1\) centreline, exact curvature, no rotation DOFs. See Solver paths.
effective tension: The OrcaFlex tension convention CableDyn reports, \(T_e = T_w + (P_oA_o - P_iA_i)\). With buoyancy applied as a distributed load it is the reported axial tension; see Conventions.
EI = 0: A line type with zero bending stiffness — routes to the positions-only cable path (chains, wire, taut synthetic moorings).
End A: The fairlead / upper end of a line (NodeA in a LINES row); arc length \(s = 0\). See Key concepts.
End B: The anchor / lower end of a line (NodeB); arc length \(s = L\).
fail closed: Reject an unsupported, ambiguous, non-finite, or inconsistent request with a named error instead of silently omitting or approximating the requested physics.
fairlead: The point where a mooring line or cable attaches to the floating platform (End A).
FOWT: Floating offshore wind turbine — CableDyn’s application domain.
Froude-Krylov: The load from the undisturbed wave pressure field, driven by the wave fluid acceleration.
generalised-alpha: The implicit time integrator of Chung & Hulbert (1993), with tunable high-frequency dissipation set by the spectral radius. See Theory.
hang-off: The upper end of a dynamic cable at the platform, where a bend stiffener limits curvature — the other fatigue-critical location.
JONSWAP: A standard irregular-sea wave spectrum (deck jonswap Hs Tp gamma dir waves); other spectra are listed in Theory.
lazy-wave: A dynamic power-cable configuration with a net-buoyant middle section that lifts an arch between the hang-off and the seabed, decoupling platform motion from the touchdown. The main application of the finite-EI path.
line: One object spanning End A → End B, built from an ordered list of sections. The unit of the CableDyn model. Different from MoorDyn, where a composite is several lines.
line type: The reusable material a section refers to by name — diameter, mass, EA, BA, EI, and the Morison coefficients.
load continuation: Applying the external load (or EI and buoyancy on the bending path) in stages and solving a Newton problem at each stage, from the seed to the full equilibrium. The static solve first tries Newton at the full load; continuation in EI is the default route of the bending path and load continuation the fallback of the cable path. The result is a true equilibrium, not a dynamic relaxation. See Theory.
Morison: The semi-empirical hydrodynamic load model (drag + inertia by section-relative flow); the coefficients Cd_n, Cd_t, Ca_n, Ca_t on a line type.
original working curve: The Syrope OWC table relating strain and tension before history-dependent modification.
sag bend: The lower curvature peak of a lazy-wave cable, below the buoyant arch — a fatigue-critical location.
section: A contiguous run of one line type with its own length and mesh density; a line is an ordered list of sections A → B (the line-and-section arrangement OrcaFlex also uses).
snap load: A sudden tension spike when a slack line goes taut; a stiff transient the implicit integrator handles at large dt (CableDyn verification and validation).
spectral radius: The generalised-α dissipation parameter \(\rho_\infty\) (deck option rhoInf); see Conventions for its range and defaults.
spread mooring: Several mooring lines radiating from a platform to anchors (e.g. three lines at 120°).
Syrope: The polyester working-curve constitutive model selected with a SYROPE: EA token. It carries a slow-strain and a running-maximum-tension history that is committed with every step and rolled back with a failed step.
taut mooring: A mooring held under high pretension so the line is nearly straight and carries little catenary sag; typically synthetic rope. Semi-taut is the intermediate regime.
touchdown: The region where a line meets the seabed; the touchdown point migrates as the platform moves.
viscoelastic rope: A synthetic rope whose slow and dynamic axial responses differ. CableDyn models it as a series-Kelvin solid (MoorDyn ElasticMod 2/3) with a committed internal state; see Theory.
VolturnUS-S: The UMaine semi-submersible platform for the IEA-15MW turbine; the reference platform of the validation cases (CableDyn verification and validation).
WaterKin: A MoorDyn-F-compatible external water-kinematics file. Current and wave modes are independent; route ownership and supported combinations are listed in Capabilities and route selection.
Wheeler stretching: A kinematics correction that evaluates linear-wave kinematics at a stretched elevation so that the fields extend to the instantaneous free surface; see Theory.