Floating collar SimObject.

Collaboration diagram for Floating collar:

Author

Per Christian Endresen

User Documentation:

Simulation model of floating collar in regular or long/short crested irregular waves. The floating collar model represents one pipe or two concentric pipes, and is based on modal superposition (Faltinsen, 2010). Linear uncoupled equations are used to simulate the dynamics in x-, y- and z-direction, while couplings to other sim objects are of a non-linear nature. Wave forces give only inertia forces and damping is given as a level of critical damping for each mode. See the master's thesis of Endresen (2011) or the OMAE-paper by Endresen et al. (2014) for more details on the mathematical model.

Parameters

Parameter	Default	Comment
Mass2D	-	Mass per unit length of the floating collar [kg]
E	-	Young's modulus for the pipe [GPa]
DistPipes	-	Distance between the pipes when the collar consists of two pipes[m]
NetOffset	0	Offset for position of net connection points relative to the ring perimeter [m]
RadiusPipe	-	Pipe radius [m]
RadiusFloater	-	Radius of the floating collar [m]
tWall	-	Thickness of the wall of the pipes [m]
DampFact	0.05	Damping factor for ring motions [-]
NumModes	15	Number of modes used in the modal superposition calculations [#]
g	9.81	Gravity acceleration [m s-2]
RhoWater	1025	Density of water used in simulation [kg m-2]
RadialSpringOn	0	Disables (0) or enables (1) springs that fix the ring to four points in space [-]
RadialSpringStiffness	1000	Stiffness of springs enabled/disabled by RadialSpringOn [-]
WaveCouplingOn	1	Enables/disables coupling between waves and horizontal movement [-]
DragCoeff	1.1	Normal hydrodynamic drag coefficient for floating collar pipes [-]
TangentialDragCoeff	0.005	Tangential hydrodynamic drag coefficient for floating collar pipes [-]
PipeVisElem	200	Number of elements used in visualisation of the pipes [#]
NumPipes	2	Number of pipes the floating consists of (may be set to 1 or 2) [#]
ViscDampSurgeOn	true	Enables/disables viscous damping in surge direction [bool]
ViscDampHeaveOn	true	Enables/disables viscous damping in heave direction[bool]
ViscNonLinDampSurgeOn	false	Enables/disables non-linear viscous damping in surge direction [bool]
ViscNonLinDampHeaveOn	false	Enables/disables non-linear viscous damping in heave direction [bool]
ViscDampSurgeAmplFact	1	Amplification factor for viscous damping in surge direction [-]
ViscDampHeaveAmplFact	1	Amplification factor for viscous damping in heave direction [-]
HorizontalBendingStiffnessParallelAxisFactor	1	Adjustment factor for rigidity in coupling between two rings with respect to horizontal bending [-]
NumberOfObservationPortsAHRS	0	Number of observation ports for acceleration, velocity, position, rotation velocity and rotation[#]
NumNetConnections	0	Number of connection points between the ring and a net structure [#]
NumBottomRingConnections	0	Number of connection points between the ring and a bottom ring [#]
NumFasteningConnections	0	Number of connection points between the ring and the bridles in a mooring system [#]
NetForcesStart	1	Simulation time at which forces from a net structure should start affecting floating collar (for stability purposes) [s]
BendingStress_pos	0	Angular position along the ring for which bending stress should be written to output [rad]
RelDispZ_pos	0	Angular position along the ring for which relative displacement in z should be written to output [rad]
RingElev_pos	0	Angular position along the ring for which ring elevation should be written to output [rad]
InitialPosition	0,0,0	Initial position of centre point of ring (x,y,z) [m]
PosNetConnections	-	Vector [NumNetConnections] describing angular position of net connection points [rad]
PosBottomRingConnections	-	Vector [NumBottomRingConnections] describing angular position of bottom ring connection points [rad]
PosFasteningConnections	-	Vector [NumFasteningConnections] describing angular position of connection points to bridles in a mooring system [rad]
Color	-	Primary color of the floater
Material	"DiffuseSpecular"	The visualization material of the floater, specified by its name.

Input ports

Tag	Size	Comment
NetConnectForce<i>	3	Force transferred from net to floating collar at net connection point with index <i>
BRConnectForce<i>	3	Force transferred from bottom ring (through chains/ropes) to floating collar at bottom ring connection point with index <i>
FastConnectForce<i>	3	Force transferred from mooring system (through bridles) to floating collar at bridle connection point with index <i>

Output ports

Tag	Size	Comment
NetConnectPos<i>	3	Position (x,y,z) of net connection point with index <i>
NetConnectVel<i>	3	Velocity of net connection point with index <i>
NetConnectTotalForce	3	Total force transferred from net to floating collar through net connection points
BRConnectPos<i>	3	Position (x,y,z) of bottom ring connection point with index <i>
BRConnectVel<i>	3	Velocity of bottom ring connection point with index <i>
BRConnectTotalForce	3	Total force transferred from bottom ring to floating collar through net connection points
FastConnectPos<i>	3	Position (x,y,z) of bridle connection point with index <i>
FastConnectVel<i>	3	Velocity of bridle connection point with index <i>
FastConnectTotalForce	3	Total force transferred from moorign system to floating collar through bridle connection points
RBMxModalForce	3	Rigid body motion forces in x direction from bridle, net and bottom ring (surveillance port)
SurfElevCenter	1	Surface elevation at the dynamic centre of the floating collar
SurfElev00	1	Surface elevation at the x,y origin (0,0)
PartVelCheck	3	Particle velocity at the point (0,0,1)
RingElevCenter	1	Elevation of the ring segment facing westward (angle of pi/2)
RingElevation	1	Elevation of the ring segment indexed by the parameter RingElev_pos
sigma_rr	1	Bending stress around the local y-axis at position given by the parameter BendingStress_pos
relDispZ	1	Relative vertical displacement between floating collar and surface at position given by the parameter RelDispZ_pos
WaveInfo	1	Dynamic pressure at the x,y,z origin (0,0,0)
FloaterCenterPos	3	Centre position of floating collar

States

Tag	Size	Comment
Position	4*NumModes	Fourier coefficients describing the position of the floater.
Velocity	4*NumModes	Fourier coefficients describing the velocity of the floater.

Revision history:

01.01.2012 PCE: Initial version