The OrcaFlex Blog

As now seems to be traditional, here at Orcina we have spent the summer months working very hard to complete a major upgrade to OrcaFlex. The result is OrcaFlex 9.3 which was formally released early in August. We have just despatched the final upgrade CD and so all customers with up-to-date MUS contracts will have the software very soon, if not already.

I should also point out that we have released a minor upgrade (version 9.3b) which fixes some bugs that have come to light in version 9.3a (the version included on the upgrade CD). As usual a patch to upgrade from 9.3a to 9.3b is available for download.

The major enhancements in version 9.3 fall into the following categories:

• Extreme value statistics post-processing of results variables.
• Text data file (in addition to existing binary data file).
• Enhanced interface to SHEAR7.
• Static state simulation files.
• Non-linear material properties for elastomeric bend stiffeners.
• API 2RD stress check.
• Coatings and linings for homogeneous pipe.
• Roll damping for vessels.
• Modal analysis improvements.
• Performance improvements.

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We have recently become aware that the version of the OrcaFlex spreadsheet released with OrcaFlex 9.2 has some performance problems. These do not always manifest themselves and we have not seen the problems ourselves. Fortunately a small number of clients have raised the issue and we have been able, with help from those clients, to diagnose the problem. We have released an updated version of the OrcaFlex post-processing spreadsheet which corrects the fault. If you are suffering from slower than usual results extraction in the spreadsheet then you are probably experiencing this problem.

While we are on the subject of the post-processing spreadsheet it seems appropriate to announce some of the changes we are making for 9.3. As you are probably aware the post-processing spreadsheet is implemented using Excel VBA macros. These link, in turn, to the OrcaFlex code through our OrcFxAPI DLL.

VBA macros have many strengths but we have become somewhat constrained by their limitations. For 9.3 we will be moving all the code into the OrcFxAPI DLL. One immediate benefit of this is that our spreadsheet template will no longer contain any macros and so will not be subject to Excel's macro security dialogs.

For 9.3 we are planning to keep the user-interface to the spreadsheet identical to previous versions. We are, however, planning one very significant change to the implementation. All previous versions processed instructions serially and made no use of the multi-core processors that are now commonplace. It is not possible to perform calculations in parallel with VBA macros. Moving the processing code into the OrcFxAPI DLL will enable us to process load case results extractions in parallel. This should significantly reduce the time taken to post-process results.

This development is currently partially complete and we have not yet implemented the multi-threading of the results extraction. I look forward to being able to write about the performance of the multi-threading aspect of this work when it is complete. Hopefully I'll be able to announce big improvements in extraction times.

We have now released the non-linear seabed soil model in OrcaFlex 9.2e (see the OrcaFlex 9.2 Support section of our website). The model has been developed by Professor Mark Randolph (Centre for Offshore Foundation Systems, University of Western Australia), a recognised expert in this field, and we have been working with Mark to implement the model in OrcaFlex.

The model is for modelling the seabed resistance for catenary pipeline contact. It takes as input the line diameter and the seabed soil geotechnical properties (undrained shear strength at the mudline, shear strength gradient with depth, soil saturated density). It then calculates the seabed reaction force on each line element as a function of the penetration, allowing for non-linear penetration resistance, hysteretic effects due to uplift and repenetration, and non-linear suction forces.

Some of the model characteristics are illustrated in the following diagram. For comparison, the standard OrcaFlex linear seabed model would give just a straight line seabed reaction curve in the diagram.

We have just released a minor upgrade to OrcaFlex, version 9.2b.

This release includes a number of bug fixes as described below:

• Certain models (typically more complex models) which use the stiffener modelling object were failing to simulate when using the implicit solver.
• Results extraction from the OrcaFlex Excel spreadsheet was sometimes hanging and eventually reporting an out of memory error in Excel.
• Batch processing had a number of separate bugs. Firstly, the auto save function was not working. In addition the option to save partially completed simulation files when cancelling a batch run was not functioning. Finally, multi-threaded batch simulations could sometimes fail, erroneously reporting "out of memory" or "could not create thread" error messages.
• Certain data items are editable even after a simulation has been run. Most notably this includes stress loading factors for Line Types. Such data items can be changed within OrcaFlex and so likewise should be editable from a batch script. However, in 9.2a the act of changing any such data item from a batch script resulted in the simulation being reset.
• There were two separate bugs relating to range graphs with vertical arc length axis (a new feature introduced in 9.2a). Such graphs were reporting incorrect values in the hint window. Additionally, instantaneous value range graphs with vertical arc length axis were not automatically ranging themselves correctly.
• Import of AQWA QTF data was failing if the data has directions which are split across more than one table.
• Cancelling certain operations (e.g. opening a graph) could leave the program in a state in which simulations could not be run.

None of these bugs lead to erroneous simulation results and so this upgrade is not a critical one.  However, a number of the bugs have significant impact on commonly used program functionality and so we would recommend that all 9.2 users upgrade to 9.2b.

A patch to upgrade from 9.2a to 9.2b can be downloaded from our website. If you would prefer to receive version 9.2b on CD please contact us.

We are very pleased to announce the release of OrcaFlex version 9.2a. We are now starting the process of producing the installation CDs and customers with up to date MUS contracts should receive the upgrade in the middle of September.

There are a great many enhancements to the software which we described in the previous blog post. The only significant change in the software from that post is that the non-linear soil model is not included in 9.2a. We have not had sufficient time to perform the testing and validation of this development to a level sufficient for release. We are continuing to work on this and hope to include the non-linear soil model in a minor 9.2 update sometime later this year.

It's been a long time since our last article and we've all been very consumed with work for OrcaFlex 9.2. We are nearly ready to release this major upgrade and are now in a position to announce the new features which it will introduce. The major enhancements fall into the following categories:

• Performance
• Bend Stiffener and Stress Joint modelling
• Multi-threaded batch processing
• Fatigue post-processing enhancements
• Non-linear seabed
• Wake deficit / interference modelling
• Wave spreading
• 6 DOF Vessel QTFs
• Python interface to OrcFxAPI

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