Python Automation

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IntroductionSession aimed at demonstrating Python being used for OrcaFlex automation:Whats it all about? Typical UsesWhy Python?Examples of:Pre-processing, Post-processingDesign OptimisationSlide #www.orcina.comOrcaFlex User Group, 2013Python Automation1Whats it all about?A means to efficiently automate tasks:Excel Spreadsheet = 1st choice for most tasksOrcFxAPI OrcaFlex Application Program InterfacePython, MATLAB, C++, Delphi

Slide #www.orcina.comOrcaFlex User Group, 2013Python Automation2Whats it all about?The first option most people think of when it comes to OrcaFlex automation is, not surprisingly, the Excel spreadsheet. This spreadsheet is supplied with the software and is set up with in-built macros to make your pre and post processing tasks more efficient and less error prone. For those of you that use the spreadsheet extensively, there is nothing wrong with using this method. It is a robust, efficient, easy to use option that is, and will continue to be, the primary automation facility that we promote for use with OrcaFlex.

However as good as the spreadsheet is, we recognise that it has some limitations. There are some tasks that you just cannot do with the spreadsheet. In addition, some OrcaFlex users simply dont want to use the spreadsheet for a variety of reasons.

To cater for this, OrcaFlex comes with a programming interface, called OrcFxAPI (short for OrcaFlex Application Program Interface). OrcFxAPI is a Windows dynamic link library (DLL) that is installed when you install OrcaFlex. The programming interface provides a doorway into OrcaFlex, through which you can pass data. So you can use the API to drive OrcaFlex from outside of the User Interface. This means being able to set data items, run simulations, extract results etc. without actually opening OrcaFlex.

You can link to the DLL using programing languages such as Python, MATLAB, C++ and Delphi. You can also link to it using other languages, with a bit of extra work. We recommend using the Python or MATLAB interfaces for automation and scripting tasks.

Why Python?Scripting language, automatic compile stepClean syntaxEasy to learnComprehensive standard libraryWell documentedIts free

Slide #www.orcina.comOrcaFlex User Group, 2013Python Automation3Typical UsesFour key ways to use Python with OrcaFlex:Pre-processingPost-processingAs an optimization / parameter study toolAs an External Function http://www.orcina.com/Support/index.php

Slide #www.orcina.comOrcaFlex User Group, 2013Python Automation4Example#1: Pre-ProcessingUsed to efficiently generate multiple load casesExcel vs Python exampleParticularly useful when there are decisions to be made as part of the automation processSuper-quick when changes are required

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Example#1: Pre-ProcessingThis example:8x weather directions2x wave periods2x conditions (SOL & EOL)2x vessel offsets (moorings intact & one line broken)=64 load cases

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Example#1: Pre-ProcessingVariables:Wave & current directionsWave period (& stage durations)Vessel initial X & Y positionVessel heading7x line sections line types to change

=large batch script table.Slide #www.orcina.comOrcaFlex User Group, 2013Python Automation7

Example#2: Post-ProcessingUsed to extract complex results:

Slide #www.orcina.comOrcaFlex User Group, 2013Python Automation8Example#2: Post-ProcessingThe task we want Python to do is: -At each sample time:Get the Crane Tips GZ-Velocity, X and Y results.Use the X and Y results to get the Environment's Z-Velocity. Calculate the relative velocity & log extremes.Slide #www.orcina.comOrcaFlex User Group, 2013Python Automation9Example#3: OptimisationUsing OrcaFlex as a statics calculation engine:Simple example to demonstrate the ideaUsing multiple static calculations to iterate towards a solutionHuge time savings over doing the task manually

Slide #www.orcina.comOrcaFlex User Group, 2013Python Automation10Example#3: Optimisationfsolve (calcDepth, initialLength)

Finds solutions to equations of the form f(x)=0, given a starting estimateThe equation we want to solve is:f(x) = towfish z position target depth = 0

calcDepthis the one dimensional function f(x)initialLengthis the starting valueSlide #www.orcina.comOrcaFlex User Group, 2013Python Automation11Further InformationUGM examples on www.orcina.com soonOrcFxAPI Help: www.orcina.com/SoftwareProducts/OrcaFlex/Documentation/Python tutorials: http://docs.python.orgLearning Python book by Mark Lutz

Questions?

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