61. Manually creating connections outside of PST

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

61.1. Tutorial overview

This tutorial covers:

Manually creating connections outside of PST
Point connections between nets and cables

61.2. Introduction

Note

Creating a large number of similar connections in the ProteusDS Simulation Toolbox (PST) can be a time consuming process with a high probability of user error.
Connections are listed in the sim.ini file, and their properties are defined in the lib.ini file. PST will automatically create the connection declaration and definition when the connection is defined through the user interface.
Bypassing PST and manually scripting or duplicating the connections can save a significant amount of time when a large number of similar connections are required.
This tutorial will manually create connections between a cylindrical net and a floating circular floating cable (such as a floating tube in a fish cage).

61.3. Setting up DObjects

Note

A cylindrical net will be attached to a floating cable using six point connections along the cable’s span.

Open a new instance of PST.
Create a new cable DObject named Floater.
Define the state of the cable by using the Polar state generation method.
Set the center position (0,0,0) m with 12 elements and a radius of 19.0986 m (120 m circumference)
Create a new DCableSegment feature called floatTube. Set the cable properties to the following:

// Axial Rigidity
$AxialRigidityMode 0
$EA 5E7

// Fluid loading
$CDc 1
$CDt 0.01
$CAc 1
// Mechanical
$EI1 2E6
$EI2 2E6
$GJ 5E5
$Diameter 0.60
$InnerDiameter 0.55
$InnerDensity 25
$Density 970
$BCID 100
$TCID 0
$CE 1
$AxialDampingMode 1
$AxialReferenceDampingRatio 0.7

// Strain Limit
$ElongationLimitMode 0

Note

The cable properties are for a 0.6 m diameter floating HDPE pipe with foam filling.

Add $CableSegment floatTube 10 to the cable input file to specify the cable properties.
Add $NodeNRing 1 to the cable input file to connect Node 0 and Node N together with continuous curvature and tangency.
Set $FluidLoadingMode 1 to specify surface integral computation for buoyancy.
Create a new net DObject named Net.
Set the state of the net using the Cylindrical state generation method.
Set the center position to (0,0,0) m with 12 elements along the circumference and 6 elements along the length.
Set the radius to 18.30282 (115 m cirfumference) and the length to 20 m.

Note

The net will have a smaller radius than the cable such that it will get stretched out upon connection to the cable.

Set $Edge2Ring 1 to connect edge 2 and 3 together with continuous curvature and tangency.
Set the dNetPanel properties to the following:

// Fluid loading
$CDc 1.05
$CDt 0.02
$CAc 1

// Hydrodynamics
$SelfShieldingMode 1

// Mechanical
$EA 1000
$EI 0
$Diameter 0.001
$Density 1500
$FilamentCount 10
$CID 1
$BCID 0
$CE 0

Note

The simulation setup should look like the following:

Fig. 61.1 Simulation setup with net and floater cable

61.4. Creating Initial Connection

Create a connection between the net and cable. Select the cable as the master and the net as the follower.
Select a point connection as the connection type.
Leave the $DNetFollowerEdge property as 0, as the top edge (edge 0) will be connected to the cable.
Leave $DNetFollowerArcLocation and $DNetFollowerEdgeLocation each as 0 to connect the cable and net together at an arc length of 0 for each respective DObject.

Note

This connection will be used as a template to duplicate outside of PST.

Save the simulation in a new folder and close PST.

61.5. Manually Duplicating Connections

In the simulation folder, open the sim.ini file in a text editor. The file should look like the following:

// Instrumentation
$IntervalOutput 0.1

// Integration
$StartTime 0
$EndTime 5
$Integrator integrator

$DObjects Cable Floater
$DObjects Net Net
$Connections Floater Net Floater_Net_Point

Note

The sim.ini file specifies the simulation integration and output parameters, as well as the names of the DObjects and connections contained within the simulation.
There is currently one connection that has been created between Floater and Net with the name Floater_Net_Point.
Connections can either be duplicated by a script that generates the necessary connection declarations and definitions, or by copy and pasting existing connections and adjusting the necessary properties.
For this example, only five duplicate connections will be made. Copying and pasting the existing connection information will be the fastest method of duplicating the connections.

Copy the connection line and paste it five times to create six total connection declarations.
While maintaining Floater and Net as the connected DObjects, change each pasted connection name to a unique name. The file should now look like the following:

// Instrumentation
$IntervalOutput 0.1

// Integration
$StartTime 0
$EndTime 5
$Integrator integrator

$DObjects Cable Floater
$DObjects Net Net
$Connections Floater Net Floater_Net_Point
$Connections Floater Net Floater_Net_Point1
$Connections Floater Net Floater_Net_Point2
$Connections Floater Net Floater_Net_Point3
$Connections Floater Net Floater_Net_Point4
$Connections Floater Net Floater_Net_Point5

Note

Now that the six connections have been declared in the sim.ini file, the properties of the connections must be specified in the lib.ini file.
The lib.ini file saves information for the library, such as properties of cable segments, net panels, connections, and many other features.

Open the lib.ini file. At the bottom of the file, the properties of the initial connection that was created in PST will appear as the following:

<Floater_Net_Point type="DCableDNetPointConnection">
// Mechanical
$DNetFollowerEdge 0
$DNetFollowerArcLocation 0
$DNetFollowerEdgeLocation 0
</Floater_Net_Point>

Copy and paste this block of text five times to create property definitions for six different connections.

Note

In each connection, the $DNetFollowerArcLocation and $DNetFollowerEdgeLocation must be adjusted to their appropriate values. The connection names also must be updated to match the names given in the sim.ini file.
The newly created library definitions should look like the following:

<Floater_Net_Point type="DCableDNetPointConnection">
// Mechanical
$DNetFollowerEdge 0
$DNetFollowerArcLocation 0
$DNetFollowerEdgeLocation 0
</Floater_Net_Point>
<Floater_Net_Point1 type="DCableDNetPointConnection">
// Mechanical
$DNetFollowerEdge 0
$DNetFollowerArcLocation 20
$DNetFollowerEdgeLocation 19.16666667
</Floater_Net_Point1>
<Floater_Net_Point2 type="DCableDNetPointConnection">
// Mechanical
$DNetFollowerEdge 0
$DNetFollowerArcLocation 40
$DNetFollowerEdgeLocation 38.333333
</Floater_Net_Point2>
<Floater_Net_Point3 type="DCableDNetPointConnection">
// Mechanical
$DNetFollowerEdge 0
$DNetFollowerArcLocation 60
$DNetFollowerEdgeLocation 57.5
</Floater_Net_Point3>
<Floater_Net_Point4 type="DCableDNetPointConnection">
// Mechanical
$DNetFollowerEdge 0
$DNetFollowerArcLocation 80
$DNetFollowerEdgeLocation 76.666667
</Floater_Net_Point4>
<Floater_Net_Point5 type="DCableDNetPointConnection">
// Mechanical
$DNetFollowerEdge 0
$DNetFollowerArcLocation 100
$DNetFollowerEdgeLocation 95.83333333
</Floater_Net_Point5>

Note

For the 120 m circumference cable, the $DNetFollowerArcLocation for each connection is specified as 0, 20, 40, 60, 80, and 100 meters, respectively.
For the 115 m circumference net, the $DNetFollowerEdgeLocation for each connection is specified as 0, 19.167, 38.333, 57.5, 76.667, and 95.833 meters, respectively.

Save and close the lib.ini file.
In the sim.ini file, set the simulation time to 20 sec.
Save and close the lib.ini file.
Open the simulation in PST.

Note

The newly created connections should show up in the connections list.

Run the simulation and view the results in PostPDS.

Fig. 61.2 Simulation results with net and floater cable