MoorDyn is a lumped-mass model for simulating the dynamics of mooring systems connected to floating offshore structures.
It accounts for internal axial stiffness and damping forces, weight and buoyancy forces, hydrodynamic forces from Morison's equation (assuming calm water so far), and vertical spring-damper forces from contact with the seabed. MoorDyn's input file format is based on that of MAP. The model supports arbitrary line interconnections, clump weights and floats, different line properties, and six degree of freedom rods.
MoorDyn is implemented both in Fortran and in C++. The Fortran version of MoorDyn (MoorDyn-F) is a core module in OpenFAST and can be used as part of an OpenFAST or FAST.Farm simulation, or used in a standalone form. The C++ version of MoorDyn (MoorDyn-C) is more adaptable to different use cases and couplings. It can be compiled as a dynamically-linked library or wrapped for use in Python (as a module), Fortran, or Matlab. It features simpler functions for easy coupling with models or scripts coded in C/C++, Fortran, Matlab/Simulink, etc., including a coupling with WEC-Sim.
Both forms of MoorDyn feature the same underlying mooring model, use the same input and output conventions, and are being updated and improved in parallel. They follow the same version numbering, with a "C" or "F" suffix for differentiation.