#include <Cable.h>

Inheritance diagram for RbCable::CableRM:

Collaboration diagram for RbCable::CableRM:

Classes
struct	element

struct	Retraction
	The retraction of the two ends as the model uses it at one instant (ClampRetraction). More...

Public Member Functions
	CableRM (const std::string &simObjectName, ISimObjectCreator *const creator)
	Reads parameters, registers states, input/output ports and shared resources.

void	OdeFcn (const double T, const double const X, double const XDot) const
	Computes object derivatives as a function of time, states and input ports.

void	InitialConditionSetup (const double T, const double const currentIC, double const updatedIC, ISimObjectCreator *const creator)

void	FinalSetup (const double T, const double const X, ISimObjectCreator const creator)

void	PreOdeFcn (const double T, const double *const X) override
	Takes the other objects' wakes at the centres of all elements for the step (MARE-0223).

const double *	forceA (const double T, const double *const X)
	Output port. Returns current force in endpoint A of cable.

const double *	forceB (const double T, const double *const X)
	Output port. Returns current force in endpoint B of cable.

void	calculations (const double T, const double *const X)
	Performs a series of computations within the cable object.

void	BuildChain (wet_cylinder_water::ChainJoints &chain, const double *X, int firstElement, int numElements) const
	Builds `chain` from elements firstElement ... firstElement + numElements - 1 at the state `X`.

void	QueryJointWater (const double T, const double *const X)

void	calculationsCommon (const double T, const double *const X) const

Protected Types
typedef Eigen::Matrix< double, 3, 3 >	mat3

typedef Eigen::Matrix< double, 3, 1 >	vec3

Protected Member Functions
void	DistributeCatenary (Eigen::Matrix< double, 3, 1 > P1, Eigen::Matrix< double, 3, 1 > P2, double L, double lengthA, double lengthB, const double currentIC, double states, int i1, int i2)

void	DistributeOnArcMidpoints (const vec3 &P1, const Eigen::Matrix< double, 2, 1 > &CatenaryU, double HorizontalDistance, double VerticalDifference, double L, const double currentIC, double states, int i1, int i2)

void	SetElementUnlessUserSet (int i, const vec3 &centre, double angle, const Eigen::Matrix< double, 2, 1 > &CatenaryU, const double currentIC, double states)

void	ReportError (const std::string &message) const

Retraction	ClampRetraction (double lengthA, double lengthB, double speedA, double speedB) const

Protected Attributes
PrintDuringExec *	m_print
	Null if the creator has no printer (`fhsim::kSimMgrKeyPrinter`), as in a unit test.

environment::SeafloorForcesInterface *	m_seafloor = nullptr
	The shared `SeafloorForces`, from FinalSetup: the soil load of each element, a rigid cylinder.

environment::wake::ElementFlowInteraction	m_flow
	The flow at the element centres, the other objects' wakes taken per step (MARE-0223); the Environment, from FinalSetup.

int	m_numElements

double	m_totalLength

double	m_radius

double	m_weight

double	m_alphaN

double	m_betaN

double	m_epsilonN

JointLaw	m_joint
	The bending and twist moments of the joints between the elements (MARE-0395).

double	m_length

double	m_mass

double	m_Ixy

double	m_Iz

bool	m_kelp

double	m_wKelp

bool	m_gaussPointDrag = true
	Gauss-point drag with the water at the joints (MARE-0396).

wet_cylinder_water::ChainJoints	m_chainJoints
	The joints of the free elements and the water at them; buffers kept from call to call.

wet_cylinder_water::ChainJoints	m_takeJoints
	The joints of all elements, where the wakes are taken (PreOdeFcn); buffers kept from call to call.

element *	m_el

ISignalPort *	m_posA

ISignalPort *	m_posB

ISignalPort *	m_velA

ISignalPort *	m_velB

ISignalPort *	m_retractedLengthA

ISignalPort *	m_retractedLengthB

ISignalPort *	m_retractedSpeedA

ISignalPort *	m_retractedSpeedB

int	m_retractedNodesA

int	m_retractedNodesB

int	m_numFreeNodes

vec3	m_ka

vec3	m_kb

ICommonComputation *	m_calcDynamics

Eigen::Matrix< double, Eigen::Dynamic, 1 >	m_lambda

Eigen::Matrix< double, Eigen::Dynamic, 1 >	m_F_MDotV

Eigen::Matrix< double, Eigen::Dynamic, 1 >	m_B

double	m_forceA [3]

double	m_forceB [3]

Detailed Description

Author: Jørgen Haavind Jensen

Simobject name for use in input file: Cable.

Retains the same structural properties as the simObject CFlexibleBottomRing, but has a simpler interface where Young's and shear moduluses are provided rather than using the \(\alpha\), \(\beta\) and \(\epsilon\) values used in CFlexibleBottomRing.

Parameters

Parameter	Default	Comment
cableLength	-	total length of the cable [m]
numElements	-	number of rigid elements in the cable [#]
diameter	-	diameter of the cable. [m]
cableWeight	-	weight of the cable [kg/m]
E-modulus	-	Young's modulus for cable material [Pa] (used as given in the compliance formulas of the class description)
G-modulus	\(\frac{E-modulus}{2.6}\)	shear modulus for cable material [Pa]
EI	\(E\,7\pi D^4/5184\)	bending stiffness of the cable [N m^2]
damping	1	structural damping of the axial constraints in the cable [-]
axialBaumgarteRate	-	Baumgarte rate of the axial constraints [1/s]; 100 to 1/dt, dt the solver's explicit step (class description)
ExternalWakeUpdate	Step	How the other objects' wakes reach the element centres; listed in fhsim_environment's doc/user/wake-parameters.md

Input ports

Tag	Size	Comment
PositionA	3	position of end-connection point A
PositionB	3	position of end-connection point B
VelocityA	3	velocity of end-connection point A
VelocityB	3	velocity of end-connection point B
RetractedLengthA	1	length of cable retracted on side A
RetractedLengthB	1	length of cable retracted on side B
RetractedSpeedA	1	retraction rate of cable retracted on side A
RetractedSpeedB	1	retraction rate of cable retracted on side B

Output ports

Tag	Size	Comment
ForceA	3	Reaction force on side A
ForceB	3	Reaction force on side B

States

Tag	Size	Comment
pos<i>	3	Position (x,y,z) of element with index <i>
vel<i>	3	Velocity of element with index <i>
theta<i>	4	Quaternion of element with index <i>
omega<i>	3	Angular derivatives of element (?) <i>

Note: Each element carries the added mass Ca rho V f normal to its axis in its translational inertia (Ca = 1, DNV-RP-C205 (2021) Table A-1; V its volume, f its wet fraction; MARE-0314, owner ruling 2026-10-13, as fhsim_base Cable and TrawlCable), so its translational inertia is m I + Ca rho V f (I - N N^T), N its axis; nothing is added along the axis, to its moment of inertia, and the change of f in time is not included. Each element's load is that of water for its wet fraction f against the wave surface (a cylinder between its ends, gated by MaxWaveElevation) and that of air for 1 - f, and in waves it takes the Morison inertia force (1 + Ca) rho f V a_n normal to its axis (owner ruling R104, CableRMWaterLoad.h); the turning added mass gives a Coriolis force on the velocity relative to the water (MARE-0323). It was all water or all air by its centre's side of the surface. The other objects' wakes are taken once per integrator step, in PreOdeFcn, at the centres of all elements and held for the step; the current and the waves stay live (MARE-0223).

The seabed: each element is a rigid cylinder (D = 2 r, the element length, its axis) at rest in the soil's frame, and the soil load of the environment's shared SeafloorForces (force and moment) is added to its load, below the seabed too: the water load always applies (MARE-0392). The soil parameters are the environment's; the cable has none.

Revision history:: Q3 2011 JHJ: Initial version.

Constructor & Destructor Documentation

◆ CableRM()

RbCable::CableRM::CableRM	(	const std::string &	simObjectName,
		ISimObjectCreator *const	creator
	)

The constructor performs all initial setup for a cable simobject. Reading in parameters, setting up communication interface i.e. output ports, input ports, and states, plus additional 'one time only' resource setup.

Parameters

[in]	simObjectName	-> The name of the simobject
[in]	creator	-> Retrieve parameters. Register states, ports and shared resources reads parameters, registers states, output and intput ports.

Member Function Documentation

◆ BuildChain()

void RbCable::CableRM::BuildChain	(	wet_cylinder_water::ChainJoints &	chain,
		const double *	X,
		int	firstElement,
		int	numElements
	)		const

Finds the joints of the free elements and queries the water at them once (MARE-0396), for the Gauss-point drag.

Parameters

[in]	T	-> Current simulation time
[in]	X	-> Current simulation state

◆ calculations()

void RbCable::CableRM::calculations	(	const double	T,
		const double *const	X
	)

Computations that are important for the cable object dynamics, but only should be called once during each time step when simulating. Results are stored in member variables in the object.

Parameters

[in]	T	-> Current simulation time
[in]	X	-> Current simulation state

◆ ClampRetraction()

Retraction RbCable::CableRM::ClampRetraction	(	double	lengthA,
		double	lengthB,
		double	speedA,
		double	speedB
	)		const

protected

The retracted lengths and speeds of the two ports under the limits of the model, one place for set-up, OdeFcn, calculations and the rendering (owner ruling D20, MARE-0413).

A negative length is 0 (with speed 0). Each end keeps two elements free, and the two ends together too: when the ends would retract more, the end that retracted more gives whole elements back until two are free. A cable of fewer than two elements does not retract.

Parameters

lengthA	Retracted length at end A [m].
lengthB	Retracted length at end B [m].
speedA	Retraction speed at end A [m/s].
speedB	Retraction speed at end B [m/s].

Returns: The limited lengths and speeds and the whole elements retracted at each end.

◆ DistributeCatenary()

void RbCable::CableRM::DistributeCatenary	(	Eigen::Matrix< double, 3, 1 >	P1,
		Eigen::Matrix< double, 3, 1 >	P2,
		double	L,
		double	lengthA,
		double	lengthB,
		const double *	currentIC,
		double *	states,
		int	i1,
		int	i2
	)

protected

Lay the free elements i1 .. i2 - 1 of a slack cable on the catenary from P1 to P2, joints closed (MARE-0398): the joints lie on the curve, each element along its chord, and the arc length is chosen so that the last joint ends on P2. Falls back to DistributeOnArcMidpoints when that arc length is not found (a nearly taut cable). User-set states stand (MARE-0394).

Parameters

L	The free length [m].
lengthA	The distance from the centre of element i1 to P1 [m].
lengthB	The distance from the centre of element i2 - 1 to P2 [m].

◆ DistributeOnArcMidpoints()

void RbCable::CableRM::DistributeOnArcMidpoints	(	const vec3 &	P1,
		const Eigen::Matrix< double, 2, 1 > &	CatenaryU,
		double	HorizontalDistance,
		double	VerticalDifference,
		double	L,
		const double *	currentIC,
		double *	states,
		int	i1,
		int	i2
	)

protected

The old placement: each element at the arc midpoint of its stretch of the catenary of arc length L, along the tangent there. Its joints are open by the arc-minus-chord differences.

◆ forceA()

const double * RbCable::CableRM::forceA	(	const double	T,
		const double *const	X
	)

See PortDefs.h

Parameters

[in]	T	-> Current simulation time
[in]	X	-> Current simulation state

Returns: -> Address of current force in endpoint A of cable

◆ forceB()

const double * RbCable::CableRM::forceB	(	const double	T,
		const double *const	X
	)

See PortDefs.h

Parameters

[in]	T	-> Current simulation time
[in]	X	-> Current simulation state

Returns: -> Address of current force in endpoint B of cable

◆ OdeFcn()

void RbCable::CableRM::OdeFcn	(	const double	T,
		const double *const	X,
		double *const	XDot
	)		const

Returns state derivatives.

Parameters

[in]	T	-> Current simulation time
[in]	X	-> Current simulation state
[out]	XDot	-> State derivatives

◆ ReportError()

void RbCable::CableRM::ReportError ( const std::string & message ) const

protected

Report a run time error through the print resource, or throw without it (MARE-0375).

Parameters

message The reason for the error.

◆ SetElementUnlessUserSet()

void RbCable::CableRM::SetElementUnlessUserSet	(	int	i,
		const vec3 &	centre,
		double	angle,
		const Eigen::Matrix< double, 2, 1 > &	CatenaryU,
		const double *	currentIC,
		double *	states
	)

protected

Set the centre, the orientation (a turn by angle about the horizontal normal to CatenaryU) and zero velocities of element i, except the states the user has set.

The documentation for this class was generated from the following file:

webfhsim/reloadrepos/fhsim_marine_elements/src/RMCable/Cable.h

Classes

Public Member Functions

Protected Types

Protected Member Functions

Protected Attributes

Detailed Description

Constructor & Destructor Documentation

◆ CableRM()

Member Function Documentation

◆ BuildChain()

◆ calculations()

◆ ClampRetraction()

◆ DistributeCatenary()

◆ DistributeOnArcMidpoints()

◆ forceA()

◆ forceB()

◆ OdeFcn()

◆ ReportError()

◆ SetElementUnlessUserSet()