Orcina news

Here you will find the latest news on the development of OrcaFlex. Alongside our LinkedIn page, it is a valuable source of information about what we are up to!

OrcaFlex turbine controller examples

OrcaFlex 10.3 introduced the turbine object, used to model horizontal axis wind turbines.

A key issue for wind turbine analysis is the modelling of the generator and blade control systems. Because these control systems are typically proprietary, OrcaFlex does not offer any built-in control system functionality. Rather, the user must specify the control systems through external functions.

When we released 10.3d, we updated the documentation to include some example external function controllers. The pertinent help topics are:

These documentation topics contain links to the controller examples which can also be downloaded directly.

Other useful sources of information for turbine modelling:

OrcaFlex 10.3 turbine validation

Following the introduction of the turbine model object in version 10.3 we have now produced a report which details the validation performed on the turbine against documented industry studies.

The validation study considers the National Renewable Energy Laboratory (NREL) offshore 5-MW baseline wind turbine, which is
recognised as an industry-standard reference turbine system.

Two separate turbine systems have been modelled and subjected to detailed analysis in OrcaFlex:

  • A land-based wind turbine system.
  • A floating wind turbine system – based on the OC3 Hywind system.

Analysis of the land-based scenario was considered to facilitate basic validation of the turbine response determined via OrcaFlex. Detailed analysis of the OC3 Hywind system was then considered to help validate the behaviour of a fully-coupled floating wind turbine system in OrcaFlex.

 

The OC3 Hywind system modelled in OrcaFlex 10.3
The OC3 Hywind system modelled in OrcaFlex 10.3

Results were compared to those from other wind turbine simulation tools; namely FAST, MSC.ADAMS, Bladed and HAWC2.

Overall, OrcaFlex has been shown to accurately capture the aerodynamic and hydrodynamic loading on the considered turbine systems. Close agreement was generally observed between the OrcaFlex results and those available from the other simulation tools – particularly with respect to the calculated turbine rotor response.

The full report is available alongside previously published OrcaFlex validation cases on the validation page here.

OrcaFlex 10.3c released

We have just released a minor upgrade, version 10.3c, which fixes a number of bugs. Full details of the changes are described here. We recommend that users of 10.3 upgrade to 10.3c.

A patch to upgrade from 10.3a or 10.3b to 10.3c can be downloaded here. The full installation program can also be downloaded from your download page. Please contact us if you do not have the link to your download page.

OrcaFlex 10.3b released

We have just released a minor upgrade to OrcaFlex, version 10.3b. Version 10.3b introduces some minor new functionality and fixes a number of bugs. Full details of the changes are described here.

A patch to upgrade from 10.3a to 10.3b can be downloaded here. The full installation program can also be downloaded from your download page. Please contact us if you do not have the link to your download page.

OrcaFlex 10.2d released

Coinciding with the release of version 10.3, we have just released a minor upgrade to OrcaFlex 10.2, version 10.2d. This 10.2 update addresses all outstanding known bugs on the 10.2 branch.

A patch to upgrade from earlier releases of 10.2 is available. Alternatively, the download page for 10.3 (sent by e-mail to your company software administration contact) offers downloads of full installation programs for older versions.

OrcaFlex 10.3 released

Once again, it’s that time of year at Orcina where we release a brand new version of OrcaFlex and so we are very pleased to announce the release of version 10.3. The software was finalised and built on 28th November.

A particular novelty this year is that we are now distributing the software electronically. Finally we have moved in to the 21st Century and will no longer be sending you CDs in the post! All clients with up-to-date MUS contracts should receive by e-mail instructions on how to download the new version.

Version 10.3 introduces much new functionality, including:

  • A new turbine object designed for modelling of floating wind turbines. This is a composite object with dedicated models for the generator, gearbox, hub and blades.
  • Quasi-dynamic mooring analysis is now possible through the addition of a comprehensive analytic catenary solver.
  • User defined results which allow you to extend OrcaFlex by defining, using Python scripts, additional results.
  • Object tags, a set of user defined name/value pairs associated with objects in an OrcaFlex model. Tags are intended for use by external functions, post calculation actions, user defined results, post-processing scripts etc.
  • Line pre-bend data can now be visualised at the point of data input, and can be specified in a more convenient format than in previous versions.
  • Friction can now be included in the line support contact model.

These are the most significant developments, in our opinion. As always there are more enhancements which are fully documented in the What’s New topic for 10.3.

Continue reading “OrcaFlex 10.3 released”

Using curvilinear constraints to impose motion

OrcaFlex has two objects whose motion can be imposed rather than calculated:

  • The vessel object through displacement RAOs, harmonic motion, time history or externally calculated motion.
  • The constraint object (added in version 10.1) through motion time histories in the constraint’s imposed displacement mode.

In addition to these more well-known methods of imposing motion, the constraint object has another mechanism that allows motion to be imposed.

Continue reading “Using curvilinear constraints to impose motion”

OrcaFlex 10.2b released

We have just released a minor upgrade to OrcaFlex, version 10.2b. This minor upgrade fixes the following bugs:

  • The following features may not have worked correctly for lines that have inactive parts: line profile graphs; fatigue analysis; splined lines in line contact relationships; penetrating lines that are around splined lines in a line contact relationships.
  • The following features may not have worked correctly for lines that use line feeding: slamming; variable added mass; rolling contact for penetrating lines that include torsion in a line contact relationship; inner lines with containment enabled in a line contact relationship.
  • Lines that use line feeding were not compatible with the following features: sea state disturbance for vessels whose sea state RAO data is interpolated on direction and period only; the Static Position (interpolated) wave calculation method; hysteretic bend stiffness; bend stiffness external results; fatigue analysis. The combination of these features with line feeding should have been blocked in version 10.2a, but was not: some combinations failed to run and others gave unexpected results.
  • The Calculate Line Lengths mode of the Line Setup Wizard was not compatible with lines that have inactive parts. This combination of features should have been blocked in version 10.2a.
  • OrcaFlex sometimes failed to run beyond statics if a line’s End A and End B initial arc lengths were both ‘~’ and the payout rate was non-zero at one or both ends. Cases that failed include lines whose Step 1 Statics Method is Quick, and models in which a static state or instantaneous value range graph is visible.
  • The assignment of sea state disturbance vessels to nodes of a line that lie exactly at section boundaries was potentially inconsistent between nodes that are initially active and those that are initially inactive.
  • Validation of contents flow and sea state disturbance vessel data was not carried out for the inactive parts of any line. It was therefore possible to run a model containing data that would otherwise have been disallowed if the line were fully active.
  • Modal analysis modes graphs, loads graphs and loads tables were reported incorrectly for lines with inactive parts.
  • OrcaFlex’s SHEAR7 and VIVA interfaces were not working correctly for lines with inactive parts.
  • A line’s actual arc length result could have been reported incorrectly if its payout rate was specified by a variable data table that truncates to zero before the end of the simulation. This only happened once the truncation to zero had occurred, and then only for lines that used smooth growth to control their payout rate. This bug could also have affected instantaneous value range graphs because the actual arc length values of the nodes are the abscissae on these graphs.
  • If an uncoupled, single-line modal analysis were performed immediately after loading up a static state simulation file, then it would have failed if the line being analysed was a penetrating line inside an outer splined line in a line contact relationship.
  • The MATLAB interface to OrcaFlex was installed incorrectly by the 10.2a installation program. Two source code files, ofx6DBuoyObject.m and ofxWaveScatter.m were missing from the installation. Scripts that depend upon these files would fail to run.

A patch to upgrade from earlier releases of 10.2 is available.

Distributed OrcaFlex 6.0c released

This is a minor update release which fixes a few bugs that have come to light since the 6.0b release. The new release is available here: Distributed OrcaFlex 6.0c

The changes include:

  • Bug fix: Sometimes, in the event of an error, the DOF Server would produce a cascade of error report files that caused the DOF Server to become unresponsive for a while. The DOF Server now only logs error details to the DOFServer.log file without generating any further error reports.
  • Bug fix: When using the command line tool ‘dofcmd’ to submit jobs, specifying an auto-save interval of 0 was not allowed. This is in fact a valid interval used to disable the auto-save.
  • Bug fix: If the DOF Server Service was restarted while jobs were still running on clients, then those jobs could end up being cancelled by the restarted DOF Server rather than re-added to the job list to continue as normal.
  • Bug fix: If jobs were submitted whilst the DOF Server was already distributing jobs to DOF Clients then the scheduler’s ramping feature was re-initiated unnecessarily. Now, the ramping feature only starts if the jobs are added and the DOF Server is idle.
  • In the client list view of the DOF Viewer, the list columns can now be resized.