40. Connecting cables using Auto-Connect

The identification tag for this tutorial is PDS-ABD. Pregenerated input files for this tutorial are found in the folder named PDS-ABD in the provided tutorial input files.

40.1. Tutorial overview

This tutorial covers:

  • Creating a bridled mooring
  • Using Auto-Connect feature to connect cables
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Fig. 40.1 Triple bridled mooring configuration

40.2. Creating a RigidBody float with a bridle mooring

40.2.1. Create a RigidBody float

Note

  • A large object will be moored using 3 bridle lines. The Auto-Connect feature in ProteusDS will be used to automatically connect the bridle lines to the main mooring line.
  • Create a new project.
  • Create a RigidBody. Leave the state with default values.
  • By design, the rigid body will be 50 % submerged in calm conditions. Specify $Mass to 50000 and set moments of inertia arbitrarily to 1e3.
  • Create a RigidBodyCuboid feature in the library with dimensions of $LengthX 30, $LengthY 5 and $LengthZ 1. The cuboid mesh should have 15, 2 and 2 segments in the X, Y and Z directions, respectively. Leave all other properties as default.
  • Add the cuboid feature to the RigidBody.

40.2.2. Create bridle lines

Note

  • Three bridle lines will connect to the rigid body at the ends and in the middle of the cuboid.
  • Create a new cable and name it bridle0.
  • Define the state of the cable to (-15,2.5,0) m for node 0 and (0,50,15) m for node N, with 10 elements. Use the straight line distance for the cable length.
  • Create a new cable and name it bridle1.
  • Define the state of the cable to (0,2.5,0) m for node 0 and (0,50,15) m for node N, with 10 elements. Use the straight line distance for the cable length.
  • Create a new cable and name it bridle2.
  • Define the state of the cable to (15,2.5,0) m for node 0 and (0,50,15) m for node N, with 10 elements. Use the straight line distance for the cable length.

40.2.3. Create main mooring line

Note

  • The main mooring line will connect to the bridle lines and will be fixed at the seabed.
  • Create a new cable and name it mooringline.
  • Define the state to have node 0 at (0,50,30) m and node N at (0,50,15) m, 5 elements, and length of cable 15 m.
  • Fix node 0 in place by setting $Node0Static 1.
  • In the feature library, create a DCableSegment feature and name it chain. The cable segment properties should be set as follows:
// Axial Rigidity
$AxialRigidityMode 0
$EA  7.464e7

// Fluid loading
$CDc 2.2
$CDt 1.15
$CAc 1
$FluidDiameter 1.27E-2

// Mechanical
$EI1 0
$EI2 0
$GJ 0
$Diameter 2.54e-2
$Density 7800
$AxialDampingMode 1
$AxialReferenceDampingRatio 0.5
$BCID 0
$TCID 0
$CE 1

// Strain Limit
$ElongationLimitMode 0

40.3. Creating cable connections

40.3.1. Using Auto-Connect feature

Note

  • The Auto-Connect feature will detect coincident end points on selected cables, and will automatically a create point connection between the cables.
  • Under the Configuration drop-down menu, select Auto-Connect Cables. This will open the Auto-Connect Wizard.
  • Select all four created cables and confirm on the next screen.

Note

  • The Auto-Connect feature will automatically create a PointMass at the connection location. Each selected cable will be connected to the PointMass as a follower. The PointMass can be used to simulate features at the connection location such as a knot, grid plate, shackle, etc.
  • Create an ExtMass feature and set it to the PointMass created by the Auto-Connect. Set the diameter of the ExtMass to 0.1 m and the density to 5000 kg/m3.
  • View the created connections in the connections window between the PointMass and the specified cables.

40.3.2. Connecting bridles to the float

  • Create a new point connection between bridle0 and the RigidBody. The connection location in terms of the rigid body local frame is (-15,2.5,0) m.
  • Repeat the process for bridle1 at the RigidBody location of (0,2.5,0) m and for bridle2 at (15,2.5,0) m.

40.4. Simulate

  • Set the depth to 30 m with a uniform current of 3 m/s at a heading of 270 deg. Apply a wave profile if desired.
  • Simulate for 30 s and view the results.