Analysis Component

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Analysis Component

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The Analysis component is used to specify the various inputs for a PipeLay analysis. It allows you to gather together a set of components of various types (such as pipelines, vessels, waves etc.) from all of those defined in a project file, and to perform various types of analyses using them. In this example the Analysis component is named ‘SCR Initiation Analysis’. The following sections provide a description of the various inputs for the analysis.

 

Properties Tab

The Properties tab allows you to specify the various properties of a particular analysis. In this example the Model is selected as ‘Model’.

 

Installation Stages Tab

The Installation Stages tab is where you actually define the various stages in your analysis. In this example there are two static stages, the second restarting from the first. Customised postprocessing is requested for the second stage, by referencing an appropriate Custom Postprocessing component, described in the following sub-section.

 

Custom Postprocessing Component

The Custom Postprocessing component allows you to request specific results in addition to those provided automatically by PipeLay. It is useful in this instance, as it allows you to monitor various parameters while the SCR initiation progresses during the second stage. So a single Custom Postprocessing component entitled ‘Custom Plots’ is created in the Postprocessing folder, and is referenced in the Custom Postprocessing drop-down list on the Installation Stages tab of ‘SCR Initiation Analysis’. Structure snapshots are requested at intervals of 0.2s from 0.0s to 1.0s (see following note) with a viewpoint of [0, 0, -1] (i.e. [X, Y, Z]) specified. The variation in effective tension in the winch cable at the installation vessel over the course of the analysis is also requested.

Note: All static analyses run from zero to one second. You have the option to specify the Number of Increments in a restart analysis. This generally defaults to 1 if unspecified – the exception being a payout analysis such as this – where the Number of Increments is chosen automatically such that no more than a single new element is introduced between successive solution time increments. In the case of this analysis the length of paid out pipe is 1750m, the maximum element length is 10m, so this leads to a chosen increment number of 175 or a time step of approximately 0.006s.

 

Parameters Tab

The Parameters tab allows you to specify what parameters you want to change during each analysis stage defined on the Installation Stages tab. The first stage determines the initial static configuration and the SCR initiation is performed in the second stage. Initiation is performed by deploying pipe from the FPU, offsetting the installation vessel and reducing the wire length. A summary of the parameters changed in the second stage of this example is provided in the table below.

Table: Summary of Parameter Changes

Parameter

Component

Value

Vessel Offset

725m Offset

Add (to Tug(1))

Pay Out (Pipe)

1750m

Pay In

Pipeline(1)_Winch Cable(1)

500m

 

Running the Analysis

We are now ready to run the analysis. While the analysis is running we can observe the analysis progress and check for warnings or errors on the Progress tab.

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