39. Bridled Mooring

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

39.1. Tutorial overview

This tutorial covers:

• Creating cable to cable connections
• Creating a bridled mooring

Fig. 39.1 Bridled mooring configuration

Fig. 39.2 Bridled mooring schematic

39.2. Creating a RigidBody float with a bridle mooring

39.2.1. Create a RigidBody float

Note

• A similar configuration to the surface mooring tutorial will be used.

• 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 800 and set moments of inertia arbitrarily to 1e2.
• Create a cylinder feature called float with diameter 1 m and length 2 m.
• Add a float to the rigid body such that it is lying flat on the water by specifying in the rigid body input section $Cylinder float 0 0 0 0 90 0.

39.2.2. Create bridle lines

Note

• The bridle lines will connect to the rigid body at the ends of the cylinder.

• Create a new cable and name it bridle0.
• Define the state to have node 0 at (-1,0,0) and node N at (0,0,10), 2 elements, and length of cable 11 m.
• Create another new cable and name it bridle1.
• Define the state to have node 0 at (1,0,0) and node N at (0,0,10), 2 elements, and length of cable 11 m.
• Leave material properties for both cables at default values.

39.2.3. 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 mooring0.
• Define the state to have node 0 at (0,0,10) and node N at (5,0,50), 10 elements, and length of cable 45 m.
• Fix node N in place by setting $NodeNStatic 1.

39.3. Connecting mooring and bridle

• Create a connection between mooring0 and bridle0. Specify mooring0 as the master and bridle0 as the follower and select point connection type.

Note

• The master constrains position and velocity of the follower and in turn the follower passes reaction loads to the master during simulation.

• The connection properties must be defined. The arcspan location along the master cable must be indicated where the end node of the follower cable is connected to. Since this is at the boundary node 0 on mooring0, leave this as the default value of $DCableFollowerLocation 0.
• Set $DCableFollowerNodeN 1 to indicate that node N of bridle0 will be connected to mooring0.
• Create a new connection between mooring0 and bridle1 in the same fashion.

39.4. Connect 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 (-1,0,0).
• Create a new point connection between bridle1 and the RigidBody float. The connection location in terms of the rigid body frame is (1,0,0).

39.5. Simulate

• Specify an environment with 50 m water depth and a 0.5 m/s uniform current with a heading of 90 degrees.
• Set the length of simulation to be 30 s. Run the simulation and view the results in PostPDS.