18. Convert a QuasiStaticCable to Cable

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

18.1. Tutorial overview

This tutorial covers:

Exporting simulation results
Converting QuasiStaticCable to Cable
Restarting a simulation from existing results

18.2. Introduction

A QuasiStaticCable simulation solves for the steady state line curvature and tension profile in response to steady forces of drag, weight, and buoyancy. It may be desired to then simulate the line in waves or other unsteady environmental forces after it has been settled. To simulate the line in unsteady environmental conditions, the QuasiStaticCable DObject must be converted to a Cable DObject, as the simulation must be completed in the time domain.

18.3. Simulation setup

Load the simulation files from the tutorial Simulate a subsurface mooring with QuasiStaticCable or Simulate a surface mooring with QuasiStaticCable. If the tutorial has not been completed, the input files can be downloaded here.
Run the simulation.
Export the simulation to a new folder. The tutorial Export simulation results describes how to export a simulation.
Open the exported simulation in PST.

18.4. Convert QuasiStaticCable to Cable

In the configuration menu, click Convert DObject(s)…

Fig. 18.1 Convert DObject menu option

Select QuasiStaticCable as the DObject type to convert from and Cable as the DObject type to convert to.

Fig. 18.2 DObject convert window

The list of DObject(s) to convert will automatically populate with all the DObjects in the simulation that match the type that is being converted.

Select the QuasiStaticCable DObject to convert and select OK.

The QuasiStaticCable DObject has now been replaced with a Cable DObject. The Cable input file will be identical to the previous QuasiStaticCable input file.

18.5. Restarting the simulation

When converting from a QuasiStaticCable to a Cable, several simulation parameters may need to be adjusted to run in the time domain. A smaller file output rate should now be used. In addition, the duration of the simulation should be adjusted, as shown in the updated simulation input file below.

// Instrumentation
$IntervalOutput 0.1

// Integration
$StartTime 0
$EndTime 20
$Integrator integrator

The integrator properties should be adjusted to the adaptive 4th/5th Runge-Kutta integration scheme, as shown in the integrator library feature below.

// Integrator parameters
$IntegratorType 1
$MinimumTimeStep 1E-15
$MaximumTimeStep 1
$InitialTimeStep 0.0001
$TruncationError 0.0001

Run the newly converted Cable simulation.

The mooring should show minimal movement since it had already reached its steady state configuration under these environmental loading conditions.