Input Reference¶

This page provides a comprehensive field-by-field reference for all OASIS input files.

dataProblem.dat¶

General simulation parameters. Each line contains a value followed by a comment.

Line	Field	Type	Units	Description
1	`gravity`	float	m/s²	Gravitational acceleration
2	`waterDensity`	float	kg/m³	Water density
3	`airAtmPresDensity`	float	kg/m³	Atmospheric air density
4	`airAtmPres`	float	Pa	Atmospheric pressure
5	`airAdiabaticDilation`	float	—	Adiabatic index for air (≈1.4)
6	`waterDepth`	float	m	Water depth (positive downward from MWL)
7	`writeTimeStep`	float	s	Output writing interval
8	`maxTimeStep`	float	s	Maximum integration time step
9	`hydroTimeStep`	float	s	Hydrodynamic force update interval
10	`fastTimeStep`	float	s	OpenFAST time step
11	`fastControllerTimeStep`	float	s	OpenFAST controller time step
12	`timeIRF`	float	s	Impulse response function duration
13	`sinkingTimeStep`	float	s	Sinking HDB update interval
14	`winchesContTimeStep`	float	s	Winches controller time step
15	`owcsContTimeStep`	float	s	OWC turbine controller time step
16	`simulationTime`	float	s	Total simulation duration
17	`rotSimpFlag`	int	—	Rotation dynamics simplification (0=No, 1=Yes)
18	`timeIntMethod`	int	—	ODE solver: 1=BDF1, 2=BDFN, 3=ESDIRK46
19	`timeIntOrder`	int	—	Solver order (for BDFN: 1–6)
20	`timeIntAdaptivity`	int	—	Adaptive time stepping (0=No, 1=Yes)
21	`timeIntJacNumStepsMax`	int	—	Max steps between Jacobian recomputation
22	`timeIntAbsTol`	float	—	Absolute tolerance
23	`timeIntRelTol`	float	—	Relative tolerance
24	`maxIterStep`	int	—	Max Newton iterations per time step
25	`readEquilibrium`	int	—	Read initial conditions from file (0=No, 1=Yes)
26	`writeEquilibrium`	int	—	Write equilibrium state to file (0=No, 1=Yes)
27	`flagStatic`	int	—	Initial mooring condition (0=Catenary, 1=Newton's)

Example:

9.81            // gravity [m/s^2]
1025.0          // waterDensity [kg/m^3]
1.225           // airAtmPresDensity [kg/m^3]
101325.0        // airAtmPres [Pa]
1.4             // airAdiabaticDilation [-]
50.0            // waterDepth [m]
0.1             // writeTimeStep [s]
0.1             // maxTimeStep [s]
0.1             // hydroTimeStep [s]
0.1             // fastTimeStep [s]
0.1             // fastControllerTimeStep [s]
60.0            // timeIRF [s]
1.0             // sinkingTimeStep [s]
0.1             // winchesContTimeStep [s]
0.1             // owcsContTimeStep [s]
300.0           // simulationTime [s]
0               // rotSimpFlag
3               // timeIntMethod (ESDIRK46)
2               // timeIntOrder
0               // timeIntAdaptivity
0               // timeIntJacNumStepsMax
1e-5            // timeIntAbsTol
1e-3            // timeIntRelTol
20              // maxIterStep
0               // readEquilibrium
0               // writeEquilibrium
0               // flagStatic (catenary)

dataBodies.dat¶

Body definitions. The number of bodies is determined automatically by counting /// header blocks.

Each body block contains:

#	Field	Type	Description
1	Body type	string	Always `RAD_DIFF`
2	Take COG from HDB	int	0=manual, 1=from database
3	DOFs list	ints	Active degrees of freedom (1–6)
4	BCP indexes	ints	Global BCP indices attached to this body
5	Wind turbine indexes	ints	Wind turbine indices (0 if none)
6	Initial position	6 floats	[x, y, z, rx, ry, rz] in global frame
7	Initial displacement	6 floats	[dx, dy, dz, drx, dry, drz] offsets
8	Hydro database filename	string	Path to `.hydb.h5` file
9	Database index	int	Body index within the hydro database (1-based)
10	Freedom flag	int	0=free, 1=locked, 2=imposed motion
11	Imposed motion filename	string	File with prescribed motion (if freedom=2)
12	Hydrostatics flag	int	0=linear, 1=nonlinear flat, 2=nonlinear with waves
13	Hydrostatics mesh filename	string	STL mesh (if nonlinear)
14	Radiation force flag	int	0=off, 1=on
15	First-order excitation flag	int	0=off, 1=on, 2=instantaneous position
16	Second-order excitation flag	int	0=off, 1=slow-drift, 2=sum-frequency
17	Viscous added mass	6 floats	Additional added mass per DOF
18	Viscous linear damping	6 floats	Linear damping per DOF
19	Viscous quadratic damping	6 floats	Quadratic damping per DOF

Example block:

//////////////////
////////////////// New body [1]
//////////////////
RAD_DIFF
0
1 2 3 4 5 6
4 5 6 7
0
0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0
../../../data/one_box.hydb.h5
1
0
none
0
none
1
1
0
0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0

dataBCPs.dat¶

Boundary Condition Points. The header declares the count of each BCP type.

1       // Number of Actuators (FairleadBCP)
2       // Number of Anchors (AnchorBCP)
0       // Number of Joints (JointBCP)
2       // Number of Fairleads (BodyBCP)
0       // Number of Elastic Anchors

Index Order

Global BCP indices are assigned sequentially: Actuators first (1..nAct), then Anchors, Joints, Fairleads, Elastic Anchors. All references in dataBodies.dat and dataLines.dat use these global 1-based indices.

BCP Blocks¶

AnchorBCP:

//////////////////
////////////////// New BCP [N] [Anchor] [i]
//////////////////
200.0 0.0 -50.0     // Position [x, y, z] in global frame
0                    // Winch ID (0 = not connected)

FairleadBCP (Actuator):

//////////////////
////////////////// New BCP [N] [Actuator] [i]
//////////////////
5.0 0.0 -2.0        // Initial position [x, y, z]
0                    // Winch ID
dataActuator_0.dat   // Prescribed motion file

JointBCP:

//////////////////
////////////////// New BCP [N] [Joint] [i]
//////////////////
100.0 0.0 -30.0      // Position [x, y, z]
0                     // Winch ID
50.0                  // Mass [kg]
0.05                  // Volume [m³]

BodyBCP:

//////////////////
////////////////// New BCP [N] [Fairlead] [i]
//////////////////
10.0 0.0 -5.0        // Position relative to body COG
0                     // Winch ID

Actuator Motion File Format¶

The dataActuator_N.dat file prescribes motion for FairleadBCP (actuator) points:

3001                                    // Number of time steps
0.0000 5.000 0.000 -2.000 0.000 0.000 0.000 0.000 0.000 0.000
0.0100 5.016 0.000 -2.000 0.000 0.000 0.000 0.000 0.000 0.000
...

Each data row has 10 columns: t, x, y, z, vx, vy, vz, ax, ay, az

dataWaves.dat¶

See Waves for detailed wave configuration.

Basic Section¶

//////////////////
////////////////// Basic wave data
//////////////////
IRR             // Wave type: REG or IRR
2.0             // Height [m] (H for REG, Hs for IRR)
10.0            // Period [s] (T for REG, Tp for IRR)
0.0             // Heading [degrees]
5.0             // Ramp time [s]

Irregular Wave Section (only if IRR)¶

//////////////////
////////////////// Irregular wave data
//////////////////
1               // Spectrum type: 1=JONSWAP, 2=Time-series, 3=Frequency-domain
0               // Piecewise flag: 0=single, 1=piecewise
//// JONSWAP
3.3             // gamma (peak enhancement)
0.0             // s (directional spreading, <1 = no spreading)
10.0            // dtheta [degrees]
0.001           // factor (min proportion of spectrum average)
0               // Read phases flag: 0=random, 1=from file
0.05            // Relative tolerance for phase check
0.1             // dt [s] for wave time series
none            // Phase filename
//// CUSTOM
none            // Data filename (wave.dat or wavefreq.dat)

dataLines.dat¶

See Mooring Lines for detailed configuration.

Each line block reads these fields in order:

Field	Type	Description
`lineType`	int	1=dynamic, 2=quasi-static
`flag_tension`	int	0=tension-only, 1=symmetric (tension+compression)
`nNodes`	int	Number of finite element nodes
`p`	int	Polynomial order per element
`L`	float	Unstretched line length [m]
`rho0`	float	Mass per unit length [kg/m]
`d`	float	Line diameter [m]
`flag_stiffness`	int	0=linear, 1=viscoelastic, >1=tabulated
(stiffness data)	...	Depends on `flag_stiffness`
`CB`	float	Seabed friction coefficient
`Cmn`	float	Normal added mass coefficient
`Cdn`	float	Normal drag coefficient
`Cdt`	float	Tangential drag coefficient
`GK`	float	Ground spring stiffness [N/m³]
`GC`	float	Ground damping coefficient
`indexSeaFloor`	int	SeaFloor index (0=flat at waterDepth)
`BCP_N`	int	BCP index at end node (global, 1-based)
`BCP_1`	int	BCP index at start node (global, 1-based)
`frictionModel`	int	0=none, 1=isotropic, 2=anisotropic
`vth`	float	Threshold velocity for stick-slip [m/s]
`ust` / `usn`	float	Static friction coefficient (tangential/normal)
`ud`	float	Dynamic friction coefficient
`deltamax`	float	Max displacement for stick phase [m]

dataSprings.dat¶

See Springs & Connectors for detailed configuration.

dataWinches.dat / dataWinchesController.dat¶

See Winches for detailed configuration.

dataSeaFloor.dat¶

Header declares counts of each seabed type:

0       // Number of bathymetry (mesh) floors
1       // Number of inclined plane floors
1       // Number of flat floors

Flat floor: single depth value (overrides waterDepth for specific lines)

50.0            // Depth [m]

Inclined plane: three points defining the plane

0.0 0.0 -50.0       // Point 1 [x, y, z]
100.0 0.0 -45.0     // Point 2 [x, y, z]
0.0 100.0 -48.0     // Point 3 [x, y, z]

Bathymetry mesh: STL filename

seabed_mesh.stl      // STL mesh file

Floor indices are assigned sequentially: bathymetry first, then inclined, then flat.