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OrcaFlex Features

Summary of key features

  • Fully 3D, non-linear, large displacement analysis.
  • Consistent and robust modelling of compression and snatching.
  • Fully coupled tension, bending and torsion.
  • Bend Stiffener / Tapered Stress Joint model generation.
  • Rayleigh damping.
  • Highly robust and accurate finite element formulation.
  • Choice of implicit or explicit time integration methods (only peer group product with this capability).
  • Fully coupled vessel/line analysis.
  • Flat, 2D profile or 3D seabed surface.
  • Non-isotropic Coulomb friction for a broad range of contact objects.
  • Best of class fully interactive GUI.
  • System visualisation as either wire frame or shaded view with perspective and hidden line removal.
  • Modal analysis.
  • Contact and clearance analyses.
  • Fatigue analysis (regular, rainflow and spectral).
  • Vortex induced vibration analysis (VIV).
  • Wake Interference Modelling (Huse, Blevins, User Specified).
  • Parallel processing to take advantage of multi-core and multi-processor hardware.
  • Automation facilities for parametric, sensitivity and loadcase studies.

Analysis

  • Full 3D modelling.
  • Complete and partial quasi-static analysis.
  • Extremely quick and robust static analysis.
  • Time domain dynamic analysis with ramp-up (to minimise starting transients).
  • Non-linear large displacement analysis, including line compression and snatch loads.
  • Modal analysis.
  • Contact, clashing and clearance analyses.
  • Fatigue analysis (regular, rainflow and spectral).
  • Fully coupled tension, bending and torsion.
  • Vessel manoeuvres (forward speed and turn rate).
  • Surface piercing fully modelled.
  • Line setup wizard to set line lengths for specified tension or top angle.

Numerical Procedures

  • Finite element model with 6 degrees of freedom at each segment end.
  • Element formulation is extremely robust, accurate and widely applicable.
  • Choice of implicit (constant or variable time step) or explicit time integration methods.
  • Parallel processing to take advantage of modern multi-core and multi-processor hardware.
  • Slow varying water particle loads can be computed at a larger time step than structural displacements.
  • Facility for FFT re-construction of wave field from single point elevation time history.
  • Fluid forces based on industry-standard Morison and cross-flow assumptions.
  • 1st and 2nd order wave loads on floaters calculated from wave load RAOs and QTFs.

Data Input

  • Interactive Graphical User Interface.
  • Visualisation as wire frame and/or shaded view with perspective and hidden line removal.
  • Powerful Model Browser to organise and manage complex models.
  • Drag and drop facilities to import data from pre-prepared OrcaFlex Library files.
  • Group, move, show/hide, locate and lock operations can be applied to individual or user defined groups of modelling objects.
  • Simple object replication.
  • Batch processing.
  • Batch script facility for generating systematic load case or parametric variations.
  • Wave scatter conversion facility for easy processing of sea scatter tables.
  • Comprehensive facilities for vessel RAO import, including graphical RAO realism checks.
  • Dedicated import facilities for AQWA and WAMIT hydrodynamic data.
  • Typical Line properties available through built-in wizard facility (for chains, ropes, wires, lines with floats, homogeneous pipes, hoses and umbilicals).
  • Pipe Plasticity wizard.
  • Powerful Variable Data structure allows many data items to be set as a function of other data.
  • External functions admit user defined calculations (e.g. heave compensation devices, DPS systems etc.)
  • Import facility for vessel motion and wave elevation time history.
  • SI, US or User Defined units.
  • Full and comprehensive context sensitive help.

Results Output

  • Native Windows user interface.
  • Shaded graphics (with perspective, lighting, hidden line removal etc.) for realistic, presentation ready, system visualisation.
  • Unlimited multiple views and graphs of the model simultaneously visible.
  • Workspace facility to manage 3D Views, graphs and spreadsheet windows.
  • Replay wizard to prepare animations of multiple simulations and / or moving camera.
  • AVI file export of animations to presentation applications such as Powerpoint.
  • Results can be monitored at run time and during simulation replay.
  • Output can be graphical (time histories, range and X-Y graphs), values (in text file or Excel spreadsheet format), statistical analysis and screen snapshots.
  • Graphs and 3D images can be pasted into other Windows applications.
  • Raw data and results of analyses can be exported as spreadsheets for further post processing.
  • Excel post processing spreadsheet allows selected data to be extracted from multiple simulation files and processed.
  • Reporting of vessel response to specified wave spectra.

Modelling Elements
Line Objects
  • For SCRs, TTRs, mooring chains, wire, ropes, homogeneous pipe, flexibles, floating hoses, cables, umbilicals etc.
  • Fully coupled bending / torsion, and axial stiffness.
  • Bend Stiffener / Tapered Stress Joint model generation.
  • Centrifugal internal flow effects included.
  • Bending stiffness, drag and added mass can be non-isotropic.
  • Axial, bending and torsional stiffness can be non-linear.
  • Hysteresis model available for bending.
  • Rayleigh damping.
  • Line centre of mass may be displaced from geometric centre.
  • Pre-bend can be modelled (e.g. spool pieces).
  • Clumped line attachments (buoyancy or weight), drag chains or flex joints.
  • Non-isotropic Coulomb friction with seabed and elastic solids.
  • Contact stiffness and damping for line clash modelling.
  • Post clash behaviour modelled.
  • Hydrodynamic and aerodynamic loading.
  • Wake Interference Modelling (Huse, Blevins, User Specified).
  • Partially submerged lines (e.g. floating hoses) handled robustly.
  • Line drag and lift coefficients can vary as Reynolds Number varies.
  • Line drag and lift coefficients can vary with proximity to seabed.
  • Compressibility specified by bulk modulus.
Vessel Objects
  • Fully coupled analysis with coupling between vessel and attached moorings, risers etc.
  • Wave frequency motions from either first order displacement RAOs or first order wave load RAOs.
  • Frequency dependent added mass and damping coefficients using the convolution integral.
  • Impose vessel manoeuvres and / or harmonic motions.
  • Impose user-defined loads for thrusters, DP etc.
  • Calculate 6 degree of freedom second order slow drift motions.
  • Use motion time history files.
  • Add wind and current force coefficients.
Buoy Objects
  • Full 3D and 6D modelling of buoys.
  • Lumped option with overall properties.
  • SPAR and Towed Fish options modelled with co-axial cylinders, each cylinder with individual properties.
  • Buoyancy and hydrodynamic loads calculated based on the instantaneous wetted surface.
  • Attach wings for hydrofoil & tail fin modelling.
  • Impose user-defined loads.
  • Compressibility specified by bulk modulus.
  • Coulomb friction with seabed and elastic solids.
Shape, Winch and
Link Objects
  • Solid shapes with elastic stiffness and Coloumb friction for contact modelling.
  • Plane, cuboid, cylinder, hollow cylinder and bellmouth options.
  • Trapped water option for modelling moonpool hydrodynamic shielding.
  • Winches, including sophisticated control of either length or tension.
  • Links, offering piecewise linear representation of non-linear stiffness and damping.

Environment
Sea
  • User defined water density, kinematic viscosity, temperature, horizontal and vertical density variation.
  • Temperature can vary with position, kinematic viscosity can vary with temperature and temperature can vary with depth.
Seabed
  • Horizontal, sloping or 2D/3D irregular seabed surface.
  • User defined stiffness and damping.
  • Non-isotropic Coulomb friction in both statics and dynamics.
Waves
  • Choice of regular wave models (Airy, Stokes' 5th order, Dean Stream Function, Cnoidal).
  • Choice of irregular wave spectra (ISSC, JONSWAP, Ochi-Hubble, Torsethaugen, User defined, time history).
  • Multiple wave trains for combinations of sea states, e.g. swell plus local waves from different directions.
  • Wave particle kinematics fully computed at all points in wave profile.
  • Choice of stretching methods (Wheeler, kinematic or extrapolation).
  • Random waves have wave spreading option.
  • Preview and selection of irregular wave profile.
  • White noise option for spectral response calculations.
Current
  • 3D current profile.
  • Both magnitude and direction can be time varying.
  • Horizontal variation factor on magnitude.
  • Multiple current data sets can be defined.
Wind
  • User defined air density.
  • Wind velocity can be constant, specified by either API or DNV spectrum, or specified by a time history file of speed and direction.
  • Vertical variation factor specified as a profile.

Vortex Induced Vibrations (VIV)
VIV Overview
  • Access to the leading methods (both frequency domain and time domain) for the analysis of Vortex Induced Vibrations, all done through OrcaFlex. This approach is key to reliable and efficient model building.
  • Application to 3D risers (not just 2D tensioned risers).
  • Consistency as only one structural model needs to be constructed which can then used with any VIV model.
  • Automatic integration with OrcaFlex's diverse modelling capabilities.
  • Quality assured implementation of time domain models.
  • Reliably tested and fully documented interfaces to Shear7 and VIVA.
  • Easy and consistent comparison between the results from different VIV models.
Shear7 Interface
  • Export Shear7 data file (.dat) based on OrcaFlex model data. This increases productivity and improves QA because you do not need to build a separate model for Shear7.
  • Export Shear7 mode shape file (.mds) from OrcaFlex using the OrcaFlex modal analysis feature.
  • Automatically selects transverse modes for mode shape file using method developed in collaboration with Shear7 author Prof K. Vandiver.
VIVA Interface
  • VIVA called directly from OrcaFlex by linking to the VIVA DLL.
  • OrcaFlex statics calculation includes enhanced drag coefficients as calculated by VIVA.
  • Enhanced drag coefficients output as results.
Wake Oscillator Models
  • Choice of Milan wake oscillator model or Iwan and Blevins wake oscillator model.
  • Attaches a wake degree of freedom to each node in the line.
  • The wake oscillator models can be disabled for selected line sections to model VIV suppression devices.
  • In-line drag enhancement.
Vortex Tracking Models
  • Choice of two CFD Vortex Tracking models that inherently account for the physics of VIV.
  • Model both in-line and transverse VIV effects.
  • Based on boundary layer theory for stagnation and separation points.
  • Uses inviscid Navier-Stokes equation for the region outside the boundary layer.
  • Much less computationally demanding than full CFD.
  • These Vortex Tracking models give useful qualitative results, but generally over-predict VIV.

Other Facilities

OrcaFlex  |  Applications  |  Features  |  Screenshots  |  Demo  |  Examples  |  Documentation  |  Validation  |  Hardware Requirements

This document is maintained by webmaster@orcina.com
Copyright © Orcina 2008

Orcina Ltd., Daltongate, Cumbria, LA12 7AJ, UK
Company no. 1996191, registered in England & Wales

Last Modified: 17th September 2008