OrcaFlex 9.1

The latest release of OrcaFlex 9.1 is OrcaFlex 9.1e. To upgrade to OrcaFlex 9.1e, download the following zip file:
  OrcaFlex-Patch-9.1a-or-9.1b-or-9.1c-or-9.1d-to-9.1e.zip (5.7 MB)
extract all the files it contains to a single folder and then run the extracted file called patch.exe.

This patch can only be applied if you are currently using an earlier release of version 9.1. You may also need access to your original OrcaFlex 9.1 installation disc when you apply it.

The new features introduced in OrcaFlex 9.1 are described below. For full details please see the OrcaFlex help file: OrcaFlex.chm (1.9 MB).

New in Version 9.1e

The implementation of lift force for Lines in previous versions of OrcaFlex was flawed. In previous versions the lift force acts normal to the line and normal to the relative flow direction.

This works well for cases where the flow is normal to the line. However if the flow is close to the line axial direction then the previous lift calculation is not appropriate. In previous versions this resulted in the lift force being over-predicted for cases where the flow direction was not normal to the line. Such cases would commonly converge poorly and/or be unstable for both statics and dynamics.

Version 9.1e corrects all these problems.

New in Version 9.1d

The Line Type chain wizard had a bug affecting normal drag diameter for all versions of 9.0 and all previous versions of 9.1. Those older versions interchanged the values of drag diameter for studless and studlink chain. This meant that the drag diameters calculated by those older versions were in error by 8%. This bug is now fixed in version 9.1d.

We have also modified the chain wizard to set the contact diameter to be the chain link envelope diameter.

New in Version 9.1c

Bug fixes


Versions of 9.1a and 9.1b had a bug which affected vessel motions and runtime performance when all of the following conditions were met:

  • The implicit integration scheme was in use.
  • A vessel had Primary Motion set to "Prescribed" or "Time History".
  • That same vessel had Superimposed Motion of "None".

When all these conditions were met then vessel motions contained errors. The errors build up gradually during the simulation which means that longer simulations are more seriously affected. In addition simulations were significantly slower than they should have been.

In version 9.1c the problem has been corrected.


Versions 9.1a and 9.1b had a bug related to the new hint window results feature introduced in version 9.1a. If a replay is paused and you hover the mouse pointer over a line then a hint window is displayed. This hint window now includes results. The code to derive these results contained a bug which corrupts Summary and Full Results for the line, and also corrupts the 3D View of the latest simulation position.

Note that the bug does not affect other results such as Time History, Statistics, Range Graph etc. It also does not affect replays. The bug is corrected in version 9.1c.

New in Version 9.1b


  • Hysteretic bend stiffness is now available when using implicit integration.
  • The Line Setup Wizard can now target horizontal end force.
  • Line Clash Energy results are now spike logged.

Modal analysis

Modal analysis formerly had a limitation that no more than 200 modes could be calculated. This has now been removed.


OrcaFlex script tables can now optionally be transposed so that load cases can be arranged in columns. Previously they had to be arranged in rows. This solves problems that some users were having with the Excel limitation of 256 columns per worksheet.

VIV Toolbox

  • The latest release of Shear7 (version 4.5) introduces changes to the format of the Shear7 data file. OrcaFlex can now output Shear7 data files for either version 4.3/4.4 or version 4.5.
  • The link to VIVA now works with Whole System Statics.

Bug fix

Spar Buoys and Towed Fish whose diameters varied along the buoy axis were drawn incorrectly in the shaded graphics mode. This bug has now been fixed.

New in Version 9.1a

Implicit integration and Whole System Statics

  • OrcaFlex now uses the Generalised-α integration scheme (version 9.0 used Newmark-β). The new integration scheme allows longer time steps which in turn means that simulations can be run many times faster than in version 9.0.
  • Rayleigh damping is now available for the implicit integration scheme. This can be used to model structural damping in lines. Different levels of damping can be specified for axial, bending and torsional response.
  • The implicit solver now has the option of using a constant time step. This is now the default option and is in general to be preferred over the variable time step option.
  • Lines which include torsion, Vessel frequency dependent added mass and damping and Drag Chain objects are all now available when using the implicit solver and whole system statics.
  • Whole system statics and implicit integration are now the default methods for new models.


  • Previous versions of OrcaFlex made various assumptions about the sense of the line which often meant that you were forced to have place End A at top of the line and End B at the bottom. For example, to model an SCR you were obliged to place End B on the seabed and connect End A to the vessel. The new Top End data item gives you the freedom to arrange your lines whichever way is more convenient.
  • The handling of friction in statics has been improved for Profile and 3D seabeds. The line is now assumed to have been laid following the shape of the seabed. This improves statics convergence for many cases and also means that the effect of axial friction is more realistically captured.
  • Previous versions of OrcaFlex included a test for unstable static solutions for Lines. Whilst this worked well in many cases, it reported false positives too frequently. That is to say cases where a stable static equilibrium had been found were too often reported as being unstable. On balance we think that the downside of reporting false positives outweighs the advantage of detecting the very unusual case of an unstable equilibrium and so we have removed the test.
  • In previous versions of OrcaFlex clump attachments interacted with elastic solids, so that contact between the clump and the solid was modelled. This happened because clumps are implemented by OrcaFlex as a special type of 3D Buoy and clumps inherited the ability to contact solids. However, we feel that this interaction is usually not desirable and so it has been disabled.
  • The Line Type Wizard for Line with Floats now sets the Contact Diameter to equal the float diameter. This allows float clearance to be reported using the Line Contact Clearance result.
  • The Line Type Wizard for Rope has been renamed Rope/Wire. Likewise the Line Type Wizard for Cable has been renamed Umbilical. The functionality is unchanged, but we feel that these names are more representative of that functionality.
  • The Line Setup Wizard can now be used to set up a line to achieve a target layback value.
  • In-plane and out-of-plane component results variables have been added for Bend Moment, Curvature, Shear Force and Bend Radius. These refer to a plane parallel to both the line's axial direction (at the specified arc length) and the vertical direction.
  • A new Net External Pressure results variable has been added. This is defined to be Internal Pressure - External Pressure.
  • A new Vertical Seabed Clearance results variable has been added.
  • For various quite technical reasons we have removed the torque per unit tension feature. We suspect that this feature is very infrequently used. Indeed we do wonder if it is used at all. We hope that this change will not cause inconvenience, but if it does then please do contact us.


  • The modelling of contact between Elastic Solids and Lines, 3D Buoys and 6D Buoys now includes friction. Friction coefficients are specified on the Solid Friction Coefficients data form.
  • The modelling of contact between the seabed and 3D Buoys and 6D Buoys now includes friction. Friction coefficients are specified on the 3D Buoy and 6D Buoy data forms.


  • The seabed can now be defined as a general 3D surface.
  • The handling of buoyancy variation with depth has been altered slightly for objects with bulk modulus not equal to Infinity. The relationship between pressure and compressed volume breaks down if the pressure exceeds the bulk modulus. Previous versions of OrcaFlex aborted the simulation if this occurred. The program will now continue the simulation if this occurs, but uses a compressed volume of zero whenever the pressure exceeds the bulk modulus.
  • The random wave search facility has been extended to allow you to search for wave events which match both a specified wave height and a specified wave period.
  • A number of different calculations for Reynolds number for flow around a cylinder are in common use. OrcaFlex now allows you the option of specifying how Reynolds number is calculated. Reynolds number is only used in OrcaFlex calculations if you have specified that drag and lift coefficients for a line are to vary as Reynolds number varies. Which method you select for calculating Reynolds number is in many ways arbitrary. The key factor is that the method chosen matches the data source used for the variable drag and lift coefficient data.


Vessel type hydrodynamic data import is available for AQWA and WAMIT output files. OrcaFlex can now automatically import the displacement and load RAO, QTF, added mass, damping and stiffness data from these files and set the vessel type conventions appropriately.


  • Control of which buoy degrees of freedom are included in the static calculation has been extended. All 6D Buoy rotational degrees of freedom can now be excluded by means of a single setting on the General data form.
  • A new declination results variable has been added for 6D Buoys.
  • A new data item called Contact Area has been added for 3D Buoys. Specifying a value of 0 allows you to disable contact for the buoy. Similar functionality is already available for 6D Buoys.


Winch connection force results variables have been added.

User Interface

  • A new Workspace facility has been added to help manage the various 3D View, graph and spreadsheet windows in OrcaFlex. This facility allows you to save your current window layout (called a workspace) which can then be restored at a later time. A single workspace can be applied to any number of OrcaFlex files which allows you to view the same collection of results windows for each different file.
  • OrcaFlex can now reconnect to a dongle if for some reason the connection to the dongle is lost. This can happen for a variety of reasons, for example if the dongle server is restarted or if the network connection to the dongle server is temporarily busy. You can even disconnect a dongle connected locally to your machine in order to loan it to a colleague temporarily! Note that the OrcaFlex simulation will pause while the dongle connection has been lost.
  • The Compare Data facility can now compare the currently loaded model with a single file on disk. This option is in addition to the existing facility for comparing two data files on disk.
  • Exported AVI files for custom replays now use the graphics mode (wire frame or shaded) specified in the custom replay.
  • The Replay menu items have been moved to a new top-level menu item. Previously they were found in a sub-menu of the View menu.
  • You can now define a north direction. If you do this then a compass is drawn on the 3D View. The compass is only drawn for plan views.
  • Results hint windowThe hint windows which are displayed when you hover the mouse over an object in a 3D View (see example) now show key results variables. Note that a calculation (statics or dynamics) has to have been performed before these results are available. The results are for the same time as used to draw the view. This means that if you pause a replay the results shown will be for the time at which the replay is paused.

Keyboard shortcut keys

A number of keyboard shortcut keys have been changed to make OrcaFlex more closely follow Windows standards.

  • CTRL+N, CTRL+O and CTRL+S now mean File | New, File | Open and File | Save respectively. Because of this we have introduced new shortcuts for View | Zoom Out (SHIFT+CTRL+I) and Replay | Replay Slower (SHIFT+CTRL+F).
  • The shortcuts for rotating the view have been changed to CTRL+ALT + ← → ↑ ↓.
  • The shortcut for opening the model browser has been changed to F6. This shortcut is also used to close the model browser. The previous shortcut F2 could not be used to close the model browser since its standard Windows meaning is to start editing the name of the highlighted item in the model browser. It is for this reason that we have made the change.

We do realise that these changes are likely to cause some confusion, at least in the short term. However, we hope that the benefit of following the standards used by other Windows programs will outweigh the downside of having to re-learn these shortcuts.


  • New results instructions have been added to the OrcaFlex spreadsheet, namely Warnings, Clear Sheet and Duplicate Sheet.
  • The Line Type Wizard can now be used from batch script using the InvokeWizard command and from the OrcaFlex API using the C_InvokeWizard function.

Wave Scatter Conversion

The log sample interval can now be varied for each load case simulation specified in the batch script output.


The detailed load case results worksheets can now be omitted using the new Output detailed load case tables option. This can significantly reduce the time required to generate the results.

VIV Toolbox

  • Transverse A/D results can now be produced for the time domain models.
  • Inline drag amplification can now be modelled for the wake oscillator models.
  • The batch script command to export Shear7 MDS files can now select which modes are to be exported.

Bug fixes

  • Modal analysis for free line ends could produce incorrect answers in certain cases. This happened if the connection stiffness data was non-zero. This data is hidden for free line ends and so you have to temporarily change the end connection to Fixed in order to check the connection stiffness value. This bug manifested itself by producing physically unrealistic mode shapes. This problem has now been fixed.
  • Line acceleration (incl. g) results variables were defined incorrectly. These results are designed to replicate accelerometer readings by "g-contaminating" the standard acceleration results. However, in previous versions, there was a simple sign error and g (in vector form) was added rather than subtracted from the standard acceleration results. This problem has now been fixed.