Torpedo Anchor

A torpedo anchor.

Collaboration diagram for Torpedo Anchor:

Simulation of a 6DOF torpedo anchor. Implementation in class TorpedoAnchor.

Author

Jorgen Haavind Jensen

Example configuration excerpt

<Lib
  LibName="fhsim_base"
  SimObject="TorpedoAnchor"
  Name="Anc"
  MaterialRho="1000"
  ShankLength="1"
  ShankDiameter="0.02"
  ShankThickness="0.01"
  FlukeSideLength="0.5"
  FlukePointLength="0.6"
  FlukeWidth="0.02"
  FlukeThickness="0.1"
/>
...
<Connection
  Anc.Force="0,0,-13.8729"
/>
...
<InitialCondition
  Anc.Position="0,0,-500"
  Anc.Velocity="0,0,0"
  Anc.Quater="1.0,0.0,0.0,0.0"
  Anc.Omega="0.0,0.0,0.0"
/>

Note

The simulation must include an Environment

The analytic Jacobian differentiates the inertia and Coriolis terms, gravity and the Force input exactly, but not the hydrodynamic drag, the soil forces or the added mass. It is complete only while the anchor is out of the water.

Input Ports

Name	Width	Description
Force	3	Force std::vector in Newton.

Output Ports

Name	Width	Description
Position	3	Anchor position in meter.
Velocity	3	Anchor velocity in meter per second.
Quater	4	Anchor orientation as quaternion.
Omega	3	Anchor angular velocity in rad per second.

Configuration parameters

Name	Width	Description
MaterialRho	1	Material density in kg per meter cubed.
ShankLength	1	Shank length [m].
ShankDiameter	1	Shank diameter [m].
ShankThickness	1	Shank thickness [m].
FlukeSideLength	1	Fluke side length [m].
FlukePointLength	1	Fluke point length [m].
FlukeWidth	1	Fluke width [m].
FlukeThickness	1	Fluke thickness [m].
Material	1	The visualization material (Default: DiffuseSpecular). Visualization builds only.

Initial conditions

Name	Width	Description
Position	3	Initial position in 3D. North, East, Down in meter.
Velocity	3	Initial velocity in meter per second.
Quater	4	Initial orientation in quaternion.
Omega	3	Initial angular velocity in rad per second.

Full example file

<Contents>
  <OBJECTS>
    <Lib
        LibName          = "base"
        SimObject        = "TorpedoAnchor"
        Name             = "Anc"
        MaterialRho      = "1000"
        ShankLength      = "1"
        ShankDiameter    = "0.1"
        ShankThickness   = "0.05"
        FlukeSideLength  = "2.5"
        FlukePointLength = "3"
        FlukeWidth       = "0.1"
        FlukeThickness   = "0.5"
     />
 
     <Lib
        LibName="environment"
        SimObject="Environment"
        Name="Env"
        Waves.Model="Component"
        Waves.NumWaves="0"
        Bathymetry.Depth="500"
        />
 
    <Lib
        LibName     = "base"
        SimObject   = "Cable"
        Name        = "C"
        cableLength = "10"
        numElements = "50"
        diameter    = "0.01"
        cableWeight = "100"
    />
 
  </OBJECTS>
  
  <INTERCONNECTIONS>
    <Connection
        Anc.Force          = "0,0,0"
        C.PositionA        = "0,0,0"
        C.PositionB        = "Anc.Position"
        C.VelocityA        = "0,0,0"
        C.VelocityB        = "Anc.Velocity"
        C.RetractedLengthA = "0"
        C.RetractedLengthB = "0"
        C.RetractedSpeedA  = "0"
        C.RetractedSpeedB  = "0"
    />
  </INTERCONNECTIONS>
 
  <INITIALIZATION>
    <InitialCondition
        Anc.Position = "0,0,-10"
        Anc.Velocity = "0,0,0"
        Anc.Quater    = "1,0,0,0"
        Anc.Omega    = "0,0,0"
    />
  </INITIALIZATION>
 
  <SIMULATION>
    <Timing TStart="0" TEnd="10"/>
    <Integrator Method="RK45_i" LogStates="0" UseRSSNorm="0">
      <StepControl StepMax="0.01" StepMin="1E-060" AbsTol="0.001" RelTol="0.001"/>
    </Integrator>
  </SIMULATION>
</Contents>

This SimObject is referred to as TorpedoAnchor