Hydrodynamic cable

A cable object with dynamic stiffness and hydrodynamic loading.

Collaboration diagram for Hydrodynamic cable:

Author

Karl-Johan Reite

Example configuration excerpt

<Lib
   LibName          = "marine_elements"
   SimObject        = "Cable/LumpedMass"
   Name             = "C"
   numElements      = "7"
   Density          = "3000"
   NumericalDamping = "0"
   Diameter         = "0.1"
   E                = "117"
   DampingRatio     = "1"
   FluidRho         = "1025"
   MaxStepLength    = "0.01"
   MaxTension       = "1000"
   MaxAcceleration  = "1005"
   StepSafetyFactor = "50"
   MeanTension      = "0"
   AdaptationPeriod = "0"
   MaterialName     = "Trawl/Wire2"
   NumFaces         = "5"
   DrawScale        = "2"
/>

Input Ports

Name	Width	Description
Length	1	The length of the cable.
PosA	3	The position of end A.
PosB	3	The position of end B.
VelA	3	The velocity of end A.
VelB	3	The velocity of end B.
velWater	3	The velocity of the water.

Output Ports

Name	Width	Description
ForceA	3	The force from end A of the cable.
ForceB	3	The force from end B of the cable.
PosA	3	The position of end A.
PosB	3	The position of end B.

Configuration parameters

Name	Width	Description
numElements	1	Number of internal mass elements (Default: 2).
Density	1	The density of the cable [kg/m³].
NumericalDamping	1	Added numerical damping on each node. The damping force is calculated as \(\vec F_i = -k m_i \vec v_i\), where \(\vec F_i\) is the added damping force, \(k\) is the numerical damping factor, \(m_i\) is the node inertia and \(\vec v_i\) is the velocity of the node (Default: 0).
Diameter	1	Diameter of the cable.
E	1	The Young's modulus (elasticity) of the cable.
DampingRatio	1	The relative axial damping of the cable. 0 is no damping, 1 is critical damping (Default: 1).
FluidRho	1	The density of the ambient fluid (Default: 1025).
MaxStepLength	1	Controls the stiffness of the cable to allow integration with step lengths up to this value (Default: 0.01).
MaxTension	1	The maximum tension. If above this value, the tension is set to this this value.
MaxAcceleration	1	The maximum acceleration. If above this value, the acceleration is set to this value (Default: 1000).
StepSafetyFactor	1	A safety factor between the MaxStepLength and the one used for calculating the stiffness of the cable (Default: 50).
MeanTension	1	Possibility to add a mean tension to correct for decreased stiffness of the cable (Default: 0).
AdaptationPeriod	1	If above zero, this tells the cable to correct its initial length to avoid length errors because of decreased stiffness (Default: 0).
MaterialName	1	The material to use for visualizing the cable (Default: Trawl/Wire2).
NumFaces	1	The number of planes to visualize the cable surface (Default: 5).
DrawScale	1	The scale of the visual appearance of the cable. This is used to make it more visible (Default: 2).

Initial conditions

This simObject does not have any initial conditions.

Full example file

<Contents>
   <OBJECTS>
      <Lib
         LibName          = "marine_elements"
         SimObject        = "Cable/LumpedMass"
         Name             = "C"
         numElements      = "7"
         Density          = "3000"
         Diameter         = "0.1"
         E                = "117"
         MaxTension       = "1000"
      />
 
      <Lib 
         LibName              = "base"
         SimObject            = "Environment/Basic"
         Name                 = "Env"
         MeanDepth            = "190"
         BottomRoughness      = "5"
         SurfaceTextureScale  = "1000"
         BottomTextureScale   = "15"
         BottomStructureScale = "50"
         TerrainRadius        = "1000"
         SurfaceDepth         = "0"
         NumTerrainRings      = "170"
      />
   </OBJECTS>
 
   <INTERCONNECTIONS>
      <Connection
         Env.CurrentVel = "2.5,0,0"
         C.PosA         = "0,0,0"
         C.VelA         = "0,0,0"
         C.PosB         = "0,0,18"
         C.VelB         = "0,0,0"
         C.Length       = "20"
      />
   </INTERCONNECTIONS>
 
   <INITIALIZATION>
      <InitialCondition
      />
   </INITIALIZATION>
 
   <INTEGRATION>
      <Engine
         IntegratorMethod           = "2"
         NumCores                   = ""
         TOutput                    = "0, 0:1:10, 30"
         LogStates                  = "0"
         Stepsize                   = "0"
         HMax                       = "0.1"
         HMin                       = "1E-060"
         AbsTol                     = "0.001"
         RelTol                     = "0.001"
         UseRSSNormInsteadOfInfNorm = "0"
         InitialStatesFile          = ""
         FileOutput                 = ""
      />
   </INTEGRATION>
</Contents>

This SimObject is referred to as Cable/LumpedMass