Branchable cable

Class containing a cable object with the ability to be branched.

Collaboration diagram for Branchable cable:

Author

Karl-Johan Reite

Date

24.07.2007 KJR: Initial version.

04.05.2010 KJR: Split into three different classes to facilitate with/without bottom contact. Simulates a cable object which is a collection of cable sections, which again are collections of one or more cable elements. The main properties of this class are an arbitrary number of cable sections, connected by an arbitrary number of nodes, with an arbitrary number of external connections. The external connections are nodes where the position and velocity is governed by the input ports. The node numbers of these must be the lowest one, starting from zero and going up to the number of external nodes minus one.

Example configuration excerpt

<Lib
   LibName                = "marine_elements"
   SimObject              = "Cable/Branched"
   File                   = "BranchedCableInput.xml"
   Name                   = "CB"
/>

Note

The input file (here called BranchableCableInput.xml) must either be specified by a path relative to the bin-folder (e.g. ../examples/input/marine_elements/BranchableCableInput.xml) , or be located in the bin-folder itself. If the file is located in the bin-folder, the parameter File above only need to contain the filename of the input file (e.g. BranchableCableInput.xml).

Example BranchableCable configuration file

The simobject takes an argument filename, which specifies a path to a file. This file contains parameters general to the branchable cable component, and specific to the cable elements.

<BranchedCable>
   <General
      NumNodes                     = "6"
      NumCables                    = "5"
      NumCableFaces                = "5"
      FluidRho                     = "1025"
      NumExternalConnections       = "4"
      NumericalDamping             = "1"
      MaxStepLength                = "0.001"
      MaxAcceleration              = "1000"
      AdaptationPeriod             = "0"
      StepSafetyFactor             = "50"
   />
   <CableElements>
      <El1
         NumElements               = "1"
         D                         = "0.025"
         E                         = "1E+011"
         NodeConnections           = "0, 4"
         Density                   = "7900"
         DampingRatio              = "0"
         AddedWeightInWater        = "0"
         MaxTension                = "1E+006"
         MeanTension               = "0"
         NumericalDamping          = "1"
         MaterialName              = "Trawl/Wire2"
         NumCableFaces             = "5"
         DrawScale                 = "3"
      />
      <El2
         NumElements               = "1"
         D                         = "0.019"
         E                         = "1E+011"
         NodeConnections           = "4, 5"
         Density                   = "7900"
         DampingRatio              = "0"
         AddedWeightInWater        = "0"
         MaxTension                = "1E+006"
         MeanTension               = "0"
         NumericalDamping          = "1"
         MaterialName              = "Trawl/Wire2"
         NumCableFaces             = "5"
         DrawScale                 = "3"
      />
      <El3
         NumElements               = "1"
         D                         = "0.019"
         E                         = "1E+011"
         NodeConnections           = "5, 1"
         Density                   = "7900"
         DampingRatio              = "0"
         AddedWeightInWater        = "0"
         MaxTension                = "1E+006"
         MeanTension               = "0"
         NumericalDamping          = "1"
         MaterialName              = "Trawl/Wire2"
         NumCableFaces             = "5"
         DrawScale                 = "3"
      />
      <El4
         NumElements               = "1"
         D                         = "0.019"
         E                         = "1E+011"
         NodeConnections           = "5, 2"
         Density                   = "7900"
         DampingRatio              = "0"
         AddedWeightInWater        = "0"
         MaxTension                = "1E+006"
         MeanTension               = "0"
         NumericalDamping          = "1"
         MaterialName              = "Trawl/Wire2"
         NumCableFaces             = "5"
         DrawScale                 = "3"
      />
      <El5
         NumElements               = "1"
         D                         = "0.019"
         E                         = "1E+011"
         NodeConnections           = "4, 3"
         Density                   = "7900"
         DampingRatio              = "0"
         AddedWeightInWater        = "0"
         MaxTension                = "1E+006"
         MeanTension               = "0"
         NumericalDamping          = "1"
         MaterialName              = "Trawl/Wire2"
         NumCableFaces             = "5"
         DrawScale                 = "3"
      />
   </CableElements>
</BranchedCable>

Input Ports

Name	Width	Description
Pos1...Pos<NumExternalConnections>	3	Position of each external connection.
Vel1...Vel<NumExternalConnections>	3	Velocity of each external connection.
Length1...Length<NumCables>	1	Length of each cable section

Output Ports

Name	Width	Description
Force1..Force<NumExternalConnections>	3	Force on each external connection.
Tension1..Tension<NumExternalConnections>	1	Tension in the element connected to each exxternal connection.
Length1...Length<NumCables>	1	The stretched length of each cable section.

Configuration parameters

Name	Width	Description
File	1	Relative path to a configuration file for the simObject. Only specifying the filename, places the file in the current working directory, i.e. the bin-directory.

Configuration parameters in the General-tag of the input file in the BranchableCable-object.

These properties may be overridden by the specification of the individual cable elements.

Name	Width	Description
NumNodes	1	The total number of nodes.
NumCables	1	The total number of cables.
NumCableFaces	1	The visual number of faces on the cable. E.g. 4 would render the cable as a bar with rectangular cross sections.
NumExternalConnections	1	The number of external connections.
FluidRho	1	The water density.
NumericalDamping	1	The amount of artificial numerical damping.
MaxStepLength	1	The maximum integration step length.
MaxAcceleration	1	An artificial limit on how fast any node is allowed to accelerate.
AdaptationPeriod	1	How fast the cable elements initial lengths are adjusted to make the actual stretched length equal that of an element with the correct elasticity.
StepSafetyFactor	1	How concervative should the integration time step adjustmnent be.
DrawScale	1	The visual scale of the cables.
MaxLengthChangeSpeed	1	How fast are the cables allowed to change length.

Configuration parameters in the CableElements-tag of the input file in the BranchableCable-object.

These parameters are specified within each cable element (see the <El> tags in the code above)

Name	Width	Description
NodeConnections	2	The nodes the element connects to.
NumElements	1	Number of internal elements.
Density	1	Density of the element.
NumericalDamping	1	Numerical damping of the element.
D	1	Diameter of the element.
E	1	Elasticity modulus of the element.
DampingRatio	1	The damping ratio of the element.
FluidRho	1	The density of the surrounding fluid.
MaxTension	1	The maximum tension of the element.
MaxAcceleration	1	The maximum acceleration of fthe element.
MeanTension	1	The expected average tension of the element.
AdaptationPeriod	1	The speed of adaptation of the element.
MaterialName	1	The name of the material to use for the visualisation of the element.
NumCableFaces	1	The visual number of cable faces of the element.
DrawScale	1	The visual scale of the element.

Initial conditions

Name	Width	Description
<name>Sec0...<name>Sec<NumCables-1>	6 per internal node of the section	The internal states of cable section N (numbered from 0).
Pos_<NumExternalConnections+1>...Pos_<NumNodes>	3	The position of connection node N. Only the internal nodes have states; the external connection nodes are driven by the Pos input ports.
Vel_<NumExternalConnections+1>...Vel_<NumNodes>	3	The velocity of connection node N. Only the internal nodes have states.

Full example file

<Contents>
   <OBJECTS>
      <Lib
         LibName                = "marine_elements"
         SimObject              = "Cable/Branched"
         File                   = "BranchableCableInput.xml"
         Name                   = "CB"
      />
 
      <Lib
            LibName = "fhsim_environment"
            SimObject = "Environment"
            Name = "Env"
            RandomSeed = "12345"
            Waves.Model="Component"
            Waves.NumWaves="0"
            Bathymetry.Depth = "190"
            Bathymetry.Model = "SumOfSines"
            Bathymetry.NumStructures = "10"
            Bathymetry.StructureLengthMax = "50"
            Bathymetry.StructureLengthMin = "10"
            Bathymetry.StructureMaxHeight = "3"
            Visual.WorldRadius = "100"
            Visual.Vertices = "170,170"
            Current.Model = "Constant"
            Current.Vector = "1,0,0"
            />
 
   </OBJECTS>
 
   <INTERCONNECTIONS>
      <Connection
         CB.Length1     = "100"
         CB.Length2     = "100"
         CB.Length3     = "100"
         CB.Length4     = "100"
         CB.Length5     = "100"
         CB.Vel1         = "0,0,1"
         CB.Vel2         = "0,0,1"
         CB.Vel3         = "0,0,1"
         CB.Vel4         = "0,0,1"
         CB.Pos1         = "0,0,-10"
         CB.Pos2         = "-10,10,10"
         CB.Pos3         = "0,10,10"
         CB.Pos4         = "10,10,10"
      />
   </INTERCONNECTIONS>
 
   <INITIALIZATION>
      <InitialCondition
      />
   </INITIALIZATION>
 
   <SIMULATION>
      <Timing TStart="0" TEnd="100"/>
      <Integrator Method="RK45_i" NumCores="1" LogStates="0" UseRSSNorm="0">
        <StepControl Step="1e-4" StepMax="100" StepMin="1e-6" AbsTol="1e-7" RelTol="1e-7"/>
      </Integrator>
      <!-- TODO migrate_v3: FileOutput="objects:states" -> configure via <OBSERVERS> section -->
   </SIMULATION>
</Contents>

This SimObject is referred to as Cable/Branched