OrcaFlex features and specification

Click here for a downloadable pdf of this technical specification.

Summary of key features

  • 3D, nonlinear, large displacement analysis
  • Fully coupled tension, bending & torsion
  • Accurate, efficient and proven FE formulation
  • Robust line compression / snatch modelling
  • External line-on-line clash & sliding contact
  • Internal line-in-line impact & sliding contact
  • Modelling of post-contact behaviour
  • Linear & nonlinear elastic contact stiffness
  • Line slug flow and free-flooding effects
  • Nonlinear time domain (implicit & explicit)
  • Linear frequency domain (1st & 2nd order)
  • Quasi-dynamic analysis
  • Constraints to fix or impose individual DoFs
  • Line feeding (haul in and pay out nodes)
  • Fully coupled vessel – line analysis
  • Comprehensive vessel load modelling
  • Multi-body hydrodynamic coupling
  • Full sum and full difference QTFs

  • Vessel wave shielding (sea state RAOs)
  • Water entry & exit slam loads
  • Full description of wind, wave and current
  • Flat, 2D or 3D seabed profile
  • Linear elastic, non-linear hysteretic & P-y soil
  • Binary and / or text input files
  • Fatigue analysis
  • Extreme value statistics
  • Modal analysis
  • VIV and interference analysis
  • Pipelay and riser code checks
  • Comprehensive range of automation tools
  • Complete Matlab, Python & DLL interfaces
  • Parallel processing (at no extra cost)
  • Batch processing for volume analyses
  • Distributed OrcaFlex optimises multi-licence use
  • Full GUI with wire frame and shaded views

Major changes in last two releases

Full details for all recent releases are available on the OrcaFlex releases page.

Version 10.3 (November-2018)
  • New turbine object
  • User-defined results
  • Quasi-dynamic analysis
  • Full field wind
  • Improved line pre-bend visualisation
  • Friction for line supports
  • Object tags
  • Post-processing multiple time histories

Version 10.2 (October-2017)
  • Line feeding: haul in and pay out nodes
  • Choice of vessel calculation mode, filtering or QTF modification
  • Morison elements, to represent viscous drag
  • Multi-level undo and redo when editing data
  • Release during simulation of supports and constraints
  • Properties report for compound objects
  • Histogram collation across multiple simulations
  • Coupled-object modal analysis

Features high on the development list

See the the OrcaFlex releases page for more information.

  • Further features for mooring analysis
  • Further features for aero-elastic modelling for wind turbines
  • Spatial variation and spatial coherence for wind
  • Diffraction analysis
  • Restarts

  • Improved lateral seabed modelling
  • Thermal / pressure expansion & contraction in pipes
  • Line results at nodes
  • Software-based licencing

Modelling objects

A wide range of objects, each very powerful, easily allows simple or complex models to be built


  • Fully coupled bending, torsion and axial stiffness
  • Bend Stiffener / Tapered Stress Joint model generation
  • Pre-bend can be modelled (e.g. spool pieces) now with visualisation tool
  • Centrifugal and Coriolis internal flow effects included
  • Slug flow and free flooding options for line contents
  • Multiple coatings and linings can be defined
  • Equivalent pipe setup tool
  • Bending stiffness, drag and added mass can be non-isotropic
  • Axial, bending and torsional stiffness can be nonlinear
  • 3D hysteresis model available for bending
  • Rayleigh damping with or without geometric stiffness
  • Line CofG may be displaced from geometric centre
  • Clumped line attachments, drag chains or flex joints
  • Non-isotropic Coulomb friction with seabed & elastic solids
  • Line Clashing for external clash modelling between lines
  • Line Contact for pipe-in-pipe, piggybacks, J-tube pulls, bend stiffeners, sliding connections, etc., allowing smooth modelling of large relative axial motion including friction
  • Hydrodynamic, aerodynamic and user-defined applied loads
  • Wake Interference (Huse, Blevins,user specified)
  • Partially submerged lines (eg, floating hoses) handled robustly
  • Line drag and lift coeffs can vary with Re or seabed proximity
  • Added mass as a function of submergence or height above seabed
  • Water entry / exit slam loads (per DNV H103, RP-C205)
  • Compressibility specified by bulk modulus
  • Choice of finite element or analytic catenary representation


  • Imposed vessel displacements:
    • first order displacement RAOs
    • prescribed and / or harmonic motion
    • time history motion files
    • externally calculated
  • Loads for calculated vessel motions:
    • first order load RAOs
    • applied loads (thrusters, ice, etc.)
    • 2nd order (low freq.) difference QTFs: full and Newman
    • 2nd order (high freq.) sum QTFs
    • wave drift damping
    • added mass and damping with convolution
    • 6DoF ‘other’ linear and quadratic damping
    • manoeuvring, current and wind loads
    • drag from attached Morison elements
    • loads from attached lines (coupled analysis)
  • Multi-body hydrodynamic coupling between floaters
  • Sea state RAOs (vessel wave shielding, wave jetting, etc)


  • Full 3D and 6D modelling of buoys
  • Lumped option with overall properties
  • SPAR option for co-axial cylinders, each with own properties
  • Fluid loads calculated based on the instantaneous wetted surface
  • Added mass as a function of submergence
  • Water entry / exit slam loads (per DNV H103, RP-C205)
  • Wings for lifting surfaces
  • User-defined imposed loads
  • Compressibility specified by bulk modulus
  • Coulomb friction with seabed and elastic solids


  • Many features to model boundary surfaces and to control lines
  • Shapes with friction for line & buoy contact
  • Plane, cuboid, cylinder (solid/hollow), & bellmouth options
  • Trapped water option for moonpool modelling
  • Drawing option for visualisation purposes


  • Winches with several length or tension control options


  • Links (springs) with linear or nonlinear stiffness & damping


  • Allow individual degrees of freedom for other objects to be constrained
  • Imposed motion via time history or externally calculated


  • Dedicated horizontal-axis turbine object
  • Aerodynamic loading via Blade Element Momentum (BEM) model
  • Blades modelled with beam elements (similar to lines)
  • Prandtl tip and hub loss models
  • Pitt and Peters skewed wake model
  • Blade pitch control via external function
  • Generator control options (constant or externally calculated)
  • Example Python controllers available (including Bladed type DLL wrapper)

Environmental description

Many options to apply environmental loads


  • User-defined water density, kinematic viscosity, temperature
  • User-defined horizontal and vertical density variation
  • Temperature can be constant or vary with depth
  • Kinematic viscosity can be constant or vary with temperature


  • Horizontal, sloping, 2D or 3D seabed surface (smooth or linear)
  • Choice of soil models:
    • linear elastic
    • nonlinear hysteretic (trenching, suction & re-penetration)
    • P-y models (API RP 2A soft clay & sand & user-defined) for vertical and near-vertical line penetration
  • Non-isotropic Coulomb friction in both statics & dynamics


  • User-defined air density
  • Wind velocity can be constant, or API or DNV spectra
  • Wind can also be a time history file of speed and direction
  • Vertical variation factor specified as a profile
  • Full field wind (varies with both space & time)


  • Regular: Airy, Stokes’ 5th, Dean Stream Function, Cnoidal
  • Irregular: ISSC, JONSWAP, Ochi-Hubble, Torsethaugen, Gaussian swell, user-defined, Time History
  • Multiple wave trains for combination sea states
  • Fluid stretching (Wheeler, kinematic or extrapolation)
  • Irregular waves have directional wave spreading option
  • Preview and selection of irregular wave profile
  • Wave kinematics choice (with individual specification for 3D & 6D buoys and lines):
    • Exact (all nodes/buoys, every time step)
    • Grid interpolation at instantaneous object positions
    • Calculation at object static positions only
  • Various wave spectrum discretisation methods:
  • equal-energy (user-defined bounds & interval) – the default
  • equal spacing (arithmetic progression)
  • geometric progression


  • 3D, non-linear
  • Both magnitude and direction can be time varying
  • Horizontal variation factor on magnitude

User interface

The OrcaFlex UI gives unrivalled flexibility in model building and analysis


  • Fully interactive native user interface
  • Visualisation as wire frame and / or shaded graphics
  • Shaded has perspective, lighting, hidden line, etc.
  • Moving camera option to track large-scale object motion
  • Add text labels at any point in 3D space or attach to objects
  • Powerful dockable Model Browser to:
    • organise and manage complex models
    • group objects in logical collections
    • copy / paste objects or groups within or between files
    • show / hide, move and locate objects or groups
    • compare object data
  • Compare files with built-in or user-specified compare tools


  • Readable, structured and self-documenting text files
  • Binary files with strong version compatibility
  • Drag-and-drop model import from other OrcaFlex files
  • Auto import for AQWA and WAMIT hydrodynamic data
  • Generic text file import for other diffraction data
  • Graphical RAO realism checks
  • Generic line properties through built-in properties wizard
  • Wizard for (hysteretic) non-linear moment-curvature data

  • Variable Data for non-constant data (drag vs. Re, etc.)
  • External functions admit user-defined calculations
  • Time history data import for:
    • vessel motions
    • wave elevation
    • wind speed & direction
  • SI, US or user-defined units
  • Full and comprehensive context sensitive help
  • Additional dedicated UI for building pipelay roller supports


  • Multiple simultaneous 3D views, results graphs & tables
  • Workspace facility to manage windows
  • Replay wizard to animate multiple simulations
  • AVI file export of animations
  • Results displayed at run time and / or simulation replay
  • Results storage optimised to minimise file size
  • GUI output can be:
    • graphical (time histories, range and X-Y graphs)
    • values (in Excel spreadsheet format)
    • statistical analysis (incl. extreme statistics)
  • GUI graphs and 3D views can be copy / pasted
  • Vessel spectral response reported at any point

Automation & productivity

OrcaFlex offers a wealth of automation and productivity-enhancing features

  • OrcaFlex comes with both 32- and 64-bit executables
  • Integral parallel processing for multi-core / processor hardware
  • OrcaFlex Excel spreadsheets for:
    • pre-processing for parametric variations of input data (either binary or text files)
    • post-processing to extract results from many output files
  • Fully multi-threaded, unattended, batch processing for:
    • data files (binary or text) for static and dynamic analysis
    • batch script files
    • fatigue analysis
    • OrcaFlex post-processing spreadsheet
    • post-processing with Python or command script
  • Batch processes above in correct order in case of dependencies
  • Low level programmatic interface, targeting C, C++ or Delphi (allows integration with 3rd party applications)
  • High-level programmatic interface, targeting Matlab or Python
  • Automated execution of SHEAR7 and VIVA from OrcaFlex

  • Conversion of storm scatter tables to regular wave scatter tables
  • Automation for model building, including:
    • wave search facility
    • Line Type and Plasticity Wizards
    • Line Setup Wizard
  • Automation for results, including:
    • vessel response reports
    • fatigue analysis
    • extreme value statistics
  • Distributed OrcaFlex optimises use of spare processor time:
    • only of benefit in a multi-licence environment
    • server program co-ordinates and allocates jobs to clients
    • clients can be set to accept or reject jobs
    • client jobs run at low priority (min. impact on other tasks)
    • client jobs can be aborted and server will re-allocate
  • Orcina Licence Monitor allows monitoring of OrcaFlex use

Fatigue analysis applications

Comprehensive fatigue analysis for all applications

  • Fatigue calculations are all multi-threaded
  • Regular, rainflow & spectral (frequency domain and response RAOs) fatigue analysis options
  • 5 fatigue damage calculation options:
    • homogeneous pipe (S-N curves)
    • stress factors for different cross-section layers (S-N curves)
    • mooring (T-N curves)
    • SHEAR7 (damage results collated & presented in OrcaFlex)
    • user-defined externally calculated stress (via external functions)
  • S-N and T-N curves can be tabulated or set parametrically

  • S-N curves have option of 4 mean stress models
  • Analysis at multiple circumference points on ID and OD
  • Analysis at multiple line positions, each with different:
    • stress concentration factors
    • thickness factors
    • S-N curves (or T-N curves for moorings)
  • Damage results as tables and / or graphs for overall damage or damage from individual cases
  • Histogram collation and individual histogram results also available

Vortex induced vibration

Simply the most comprehensive set of VIV tools in one program


  • Uses the leading methods for the analysis of VIV
  • All methods are coupled, applying VIV loads to the line
  • Generalised to 3D behaviour (not just 2D)
  • Highly efficient as all VIV models use same FE model
  • Tested and fully documented SHEAR7 and VIVA interfaces
  • Quality-assured implementation of time domain models
  • Consistent results comparison from different VIV models


  • Export input data to run SHEAR7 / VIVA off-line from OrcaFlex
  • Call either directly from OrcaFlex with either a user-specified or OrcaFlex-derived mode shape file
  • Automatically selects transverse modes for mode shape file
  • OrcaFlex statics couples with SHEAR7 / VIVA enhanced drag
  • Results (incl. fatigue) presented in OrcaFlex; for SHEAR7, optionally aggregate fatigue damage via the OrcaFlex fatigue form


  • Milan or Iwan and Blevins wake oscillator models
  • Model VIV suppression by turning off for selected line sections
  • In-line drag enhancement included


  • Two approaches which model the physics of VIV
  • Both in-line and transverse VIV effects included
  • Boundary layer theory for stagnation and separation points
  • Inviscid Navier-Stokes equation used outside the boundary layer
  • Much less computationally demanding than full CFD

Numerical procedures

OrcaFlex is the most robust and therefore most widely applicable in its peer group

  • Finite element with 6 DoF at each node
  • Constraints to fix or impose individual DoFs
  • Connect mid-Line nodes to other objects
  • Optional 3 DoF line element for optimal performance
  • Element formulation is extremely robust and accurate
  • Element is proven and widely applicable
  • Fully coupled tension, bending and torsion
  • Full 3D model building and analysis
  • Non-linear large displacement analysis
  • Variety of dynamic solution methods:
    • Nonlinear time domain implicit (constant or variable Δt)
    • Nonlinear time domain explicit
    • Linear frequency domain (1st & 2nd order)
  • FFT reconstruction of wave field from wave elevation time history
  • Fluid forces based on Morison and cross-flow assumptions

  • 3 optimisations for wave kinematics calculations
  • Extremely quick and robust static analysis
  • Dynamics ramped-up (to eliminate starting transients)
  • Robust line compression and snatch load modelling
  • Line and system modal analysis (shapes and loads)
  • Contact, clashing and clearance analysis
  • Linear & non-linear elastic contact stiffness for seabed, elastic solids, line contact and supports
  • Vessel manoeuvres (forward speed and turn rate)
  • Coupled and uncoupled vessel / line analysis
  • Surface piercing fully modelled
  • Setup Wizard to set line length for target end conditions
  • Pressure effects on line EI can be separate for statics & dynamics
  • Code checks (API RP 2RD, API RP 1111, DNV OS F101, DNV OS F201 and PD 8010)