OrcaFlex 9.3

The latest release of OrcaFlex 9.3 is OrcaFlex 9.3c.

To upgrade to OrcaFlex 9.3c from earlier versions of 9.3, download the following zip file: OrcaFlex-Patch-9.3a-or-9.3b-to-9.3c.zip (6.6 MB). Extract the contents of the downloaded zip file to a single folder and then run the extracted file called patch.exe.

See below for details and status of any known bugs in version 9.3.

The new features introduced in OrcaFlex 9.3 are described below. For full details please see the OrcaFlex help file: OrcaFlex.chm (2.2 MB).

New in version 9.3c

Static state results

Static state results (e.g. static state range graphs) are now available for dynamic simulation files.

This change has been implemented by returning results based on the first log sample from the dynamic simulation. As a consequence of this the first log sample of the simulation is now sampled differently from previous versions of the program. In previous versions the first sample was taken after dynamics had started, but before the first time step integration. In this version of the program the first log sample is taken immediately before dynamics begins.

The reason for this change is so that the first log sample really does contain the static state results. For example, consider a line end which is released at the beginning of the build-up stage. Once the line end has been released, the effective tension at that end will be zero. In statics, before the end is released, the effective tension will, typically, be non-zero. The change described above results in the non-zero static state value being logged as the first log sample – previous versions logged the zero tension value corresponding to the released state.

Please note that you should re-run dynamic simulations with version 9.3c or later before making use of this new capability. This ensures that simulation files incorporate the logging change described above.

MATLAB interface with OrcaFlex

The OrcaFlex programming interface is now available from MATLAB.

Statics Friction for Lines

The handling of axial friction in statics has been improved for non-horizontal seabeds.

Bug fixes

• Static state wake interference results (Wake Velocity Reduction Factor, Wake Cd, Wake Cl) are incorrect for static state simulation files. The results are correct when extracted directly after the static calculation is performed.
• Solid Contact Force results for bend stiffener attachments are always reported as zero in static state, even if there is contact with an Elastic Solid.
• Static state tension results for bend stiffener attachments are incorrect when the graph is created immediately after a modal analysis has been performed.
• Incorrect values of Dry Length are reported for Spar Buoys and Towed Fish in the Summary/Full Results tables in static state.
• OrcaFlex sometimes reports a Control 'BatchList' has no parent window error message at program shutdown. This error is in fact benign.
• For certain OrcaFlex data forms, data in library files cannot be viewed and an Assertion failed error message is displayed.
• The SHEAR7MdsFile batch script command can fail and produce an Access violation error message. This occurs when there are no transverse modes – usually due to no current being applied.
• OrcaFlex simulation files which fail due to dynamic instability when run using the batch script RunDynamics command are not saved.
• Cancelling from the batch form can produce an Access violation error message. This occurs only when using the Check button, only when checking statics and only when Whole System Statics is being performed.
• Cancelling from the batch form fails to cancel jobs which are performing Whole System Statics if you select the save partially completed simulation files option. Any such jobs continue running until their statics calculations are complete.

These bugs are all fixed in version 9.3c.

New in version 9.3b

Profiled seabeds now support up to 100,000 data points. Previously the limit was 10,000 points.

Bug fixes

• Saving files to a network share would, in certain circumstances, result in failure with an "Access is denied" error.
• The end nodes of a stiffener line could, in certain circumstances, clash with its associated product line. This is a bug since a stiffener should not clash with its associated product line. The bug is segmentation dependent and is unlikely to occur for most typical bend stiffener models.
• Using the mouse scroll wheel with no child windows (e.g. 3D Views, Graphs etc.) open generates an "Access Violation" error message.

These bugs are all fixed in version 9.3b.

New in version 9.3a

Extreme Statistics

Extreme Statistics Results are available for time history variables. Return values are estimated for a user-specified time duration, based on the time history of a selected variable. Rayleigh, Weibull or Generalised Pareto distributions can be fitted. For the latter two, confidence limits are estimated for the return level and diagnostic graphs are presented indicating the goodness-of-fit of the selected model.

Text data file

OrcaFlex models can be saved to text data files in addition to the traditional binary .dat data file. Text data files can be edited in any standard text editor and are readable, well structured and self-documenting. The text data file offers benefits for QA and automation in particular and is intended to complement, rather than replace, the binary data file.

Static state simulation files

• Results from static analyses can now be saved to simulation files. Such static state simulation files can be re-opened and static state results can then be extracted.
• The OrcaFlex batch form can now perform static analysis and save simulation files containing the results of that analysis.
• A new batch script command, RunStatics, has been added. This performs a statics calculation and then saves the results to a simulation file.
• The OrcaFlex spreadsheet can load static state simulation files and post-process statics state results.
• You can use static state simulation files in a custom replay to show a series of static snapshots. This can be significantly faster than in previous versions which typically calculated statics for each snapshot every time the replay was started.

Performance improvements for drag-dominated systems

Previous releases of the program have suffered from performance problems when modelling certain drag-dominated systems. Most commonly this affected towed-array systems with high tow speeds. Such systems could suffer from poor convergence in both statics and implicit dynamics. Dynamic simulations could require very short time steps and often were faster performed with the explicit solver. These performance problems have been comprehensively addressed by this release of the program.

The performance problems were caused by previous versions omitting drag-related terms in the system Jacobian matrix. For the vast majority of systems modelled in OrcaFlex the statics and dynamics convergence is dominated by the structural terms in the Jacobian matrix. In all previous versions of the program we therefore omitted the Jacobian terms related to drag. The Jacobian matrix is only used for the purposes of obtaining convergence of the static or dynamic equilibrium equations and does not affect results. Consequently omitting terms which do not affect convergence is reasonable and actually results in better performance. However, it has become clear that the drag-related terms are sometimes significant (e.g. when the relative fluid velocity is high) and so we have now included them.

In our experience drag-dominated systems typically require shorter time steps than structurally-dominated systems, even if the Jacobian terms related to drag are included. For typical towed array systems we have found that a time step of 0.025s produces stable convergence in dynamics although different systems may have different time step requirements.

Performance improvements for systems with line clashing

We have made similar improvements for systems which include line clashing. Previous versions of OrcaFlex did not include any Jacobian contributions related to line clashing. As described above this can result in poor convergence of implicit dynamic simulations. This version of the program now includes the Jacobian contributions related to line clashing. For many systems this results in better convergence and means that longer time steps can be used.

Although the inclusion of the Jacobian contributions results in more stable convergence, you still should use a short enough time step to achieve your desired level of accuracy. Line clashing commonly leads to significantly non-linear responses. Hence, shorter time steps are required for accurate simulations than is the case for systems with less non-linearity.

Lines

• For homogeneous pipes the Young's modulus can now be a variable data item. This is defined by a stress-strain relationship specified either by a Ramberg-Osgood curve or by a table of strain and stress values. This enhancement allows better modelling of non-linear behaviour of elastomeric bend stiffeners and plastic deformation of steel pipes during installation.
• The Plasticity Wizard no longer requires a Maximum Curvature to be specified and instead uses a value based on the stress-strain data.
• Coatings and linings can now be modelled for homogeneous pipe line types. These are typically used with steel pipes to model the additional mass and displacement of concrete coatings, plastic linings etc.
• New data items and results variables have been added which implement the strength code checks from API RP 2RD.
• A Layback results variable has been added for lines.
• The Line Type Wizard for Homogeneous Pipe now creates data for a General Category Line Type. In version 9.2 the Wizard created data for a Homogeneous Pipe Category Line Type. We now recognise that the change to the Wizard's behaviour in 9.2 was rather unhelpful given the availability of Homogeneous Pipe Category Line Types. Consequently we have reverted the Wizard's behaviour to that exhibited by version 9.1 and earlier. Now that the Homogeneous Pipe Category can model non-linear bending and supports coatings and linings we suspect that the Line Type Wizard for Homogeneous Pipe will be very seldom used.
• The User Specified Starting Shape statics method now allows you to specify node orientations if torsion is being modelled.

Vessels

• Calculated vessels can now include the effects of roll damping. These effects are included in a simple model offering both linear and quadratic damping terms.
• A number of new results variables have been added: Sea Surface Clearance, Acceleration (incl. g), Angular Velocity and Angular Acceleration.

Buoys

• A connections table has been added to the Summary and Full Results tables for both 3D and 6D Buoys. This table contains the same information as the connections table for Vessels.
• A number of new results variables have been added for 6D Buoys: Acceleration (incl. g), Angular Velocity and Angular Acceleration.

Links and Winches

• Links and Winches can can be connected to Lines in a more general way. In previous versions of the program such connections had to be made at the centreline of the Line. The connections can now be offset from the centreline. Note that this does require torsion to be modelled in the Line.
• The Link data form now allows you to plot graphs of the non-linear stiffness and damping data.

Shapes

Contact force results are now available relative to local solid axes.

Environment

• A new wave type has been added to model a Gaussian Swell wave spectrum. Such a spectrum is typically used to model long period swell seas.
• The wave spectrum discretisation algorithm has been generalised and improved. You can now specify minimum and maximum relative frequency ranges which determine the range of frequencies considered by the spectral discretisation algorithm. More importantly you can impose a maximum component frequency range which prevents OrcaFlex using wave components which cover too large a frequency range.
• Sea results are reported at a specified point X,Y,Z. You can now use the value '~' for Z which is interpreted as meaning the instantaneous sea surface elevation.
• The Wave Components report now includes spectral moments m₀ up to m₄ – previously it only included m0, m1 and m2. The spectral bandwidth parameter epsilon is also now included.
• 3D seabed data points can be excluded from wire frame drawing which can sometimes be useful for models with extremely large numbers of 3D seabed data points. Such models can take a very long time to draw and drawing performance can be improved by omitting the drawing of the data points.
• The 3D seabed triangulation algorithm has been enhanced. A new data item, minimum edge triangulation angle, has been added. This gives a degree of control over how the triangulation is performed at the edges of the seabed data set.

VIV

• The SHEAR7 interface has been extended to allow SHEAR7 to be called directly from OrcaFlex to perform coupled VIV analyses. In addition to the benefits of coupling, the direct SHEAR7 interface greatly simplifies the automation and file management issues related to running SHEAR7 from OrcaFlex.
• SHEAR7 data file export now has an option to control how the current profile is discretised. Previous versions of OrcaFlex produced a table with one entry per node. When segment lengths are small this can give rise to numerical problems in SHEAR7. OrcaFlex now allows you to produce a current profile table for SHEAR7 with regularly spaced entries. This is now the default option with a default target spacing of 10m.
• Mode curvature in the the SHEAR7 .mds file is now calculated with a more accurate analytic method than previous versions which used a perturbation method.

User Interface

• The INSERT and DELETE keys can be used to insert and delete rows in a data table. In previous versions of the program only a single row at a time could be inserted or deleted. Multiple rows can now be inserted and deleted if multiple rows of the table are selected.
• Linked Statistics results tables now include estimates of m₀, m₂, m₄, T_c (mean crest period) and the spectral bandwidth parameter e. These are in addition to estimates of mean, standard deviation and T_z (mean up-crossing period) which were reported by previous versions.

Modal Analysis

• Seabed friction is now modelled slightly differently for modal analysis. Previous versions of the program were somewhat prone to modal analysis failures related to seabed interaction and this change has been implemented to avoid such failures.
• Modal analysis is now available for lines with torsion.
• Mode shapes can now be reported with respect to either global axes directions or node axes directions.
• Mode shape views can now be animated and node axes for mode shapes can now be drawn.

Fatigue analysis

• Homogeneous pipe fatigue can now be performed at either the inner or outer fibre of the pipe. Previously the analysis was always performed at the outer fibre.

Batch processing and Automation

• A pause button is now available on the batch processing form.
• Individual tasks may be aborted via the popup-menu on the batch processing form.
• When a batch processing run completes, any tasks which failed are moved to the end of the batch list. This makes it easy to identify which jobs failed, expecially when the batch job contains a large number of tasks.
• The wave search facility is now available from batch script using the new command WaveSearch.
• The InvokeWizard batch script command can now be used to invoke the Plasticity Wizard.

OrcaFlex Programming Interface

• Modal analysis is now available via the OrcaFlex Programming Interface through the following functions: C_CreateModes, C_DestroyModes, C_GetModeDegreeOfFreedomDetails, C_GetModeDetails and C_GetModeSummary. The Python interface also supports modal analysis.
• New functions have been added to the OrcaFlex Programming Interface: C_CalculateLinkedStatisticsTimeSeriesStatistics, C_CalculateTimeSeriesStatistics, C_SaveExternalProgramFile, C_GetBinaryFileType, C_GetDataRowCount, C_SetDataRowCount, C_GetWaveComponents2, C_DisableInMemoryLogging.
• A New field (ObjectHandle) has been added to the TVarInfo structure.
• The Python interface has been expanded significantly and now exports the same level of functionality as the C interface.

For full details please refer to the OrcFxAPI documentation.

Bug fixes

• The shaded drawing interpretation of Vessel Type wire frame data was not being scaled correctly in particular circumstances. This bug occurred when the Vessel Type length was different from the Vessel length and the edge diameter was non zero.
• SHEAR7 .mds file export was incorrect for length units other than m or ft.
• The Lines with Floats Wizard was not working when the base Line Type was a Homogeneous Pipe.

These bugs are all fixed in version 9.3a.

Known bugs in 9.3c

The bugs listed below have all been fixed internally and the fixes will be included in version 9.3d.