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Home > Version History > What was New in Version 4.4

What was New in Version 4.4

User Interface

  • Copy/Paste of model components: All model components can now be copied and pasted keeping connections for the new component similar to those of the original object. You may now for instance copy any Line several times without having to specify again associated boundary conditions. The copy/paste feature of course allows to select either if you wish to keep connections unchanged or if you wish to set all connections for the new object free as previously.

  • Copy/Paste of Analyses Sets: Analyses Sets can now be copied and pasted. This avoids having to redefine all parameters, including predefined results, when creating a new Set of Analyses that only slightly differs from an existing one.

  • Save As feature: Model files opened with Version 4.4 may now be saved under Version 4.3 file format to ensure backward compatibility. To this purpose, use the Save As feature and select the appropriate *.DSK filter (Model Files for Version 4.3) from the Save As dialog. All non-available model components in Version 4.3 such as Winch Lines or Ballast will however not be saved.

  • Working directory: External text data files that come in addition to your DSK model file may sometimes be used in order to define links to HDB files, surfaces, imposed motions, or scatter diagrams, etc. All these external files may be defined using the absolute path and filename or relative path and filename. Another option has been added based on user-defined working directories. A working directory may now be defined from the Settings menu. This working directory may then be invoked in any filename by using the $CURPATH characters string. Using working directories provides more flexibility when moving all model files from a machine to another and ensure that you will not need to check and update all filenames before running your analyses.

  • Management of licenses: Batch jobs including series of analyses used to stop with previous Versions in case your network license had became temporarily unavailable due to maximum number of users reached or network connection failure. We may now provide upon request an upgraded ISYCNTRL.DLL dynamic link library that will ensure that batch jobs would not stop anymore in such an event, since the software will permanently ask for the license over the next 24 hours, until the license is found again. This dynamic link library is however not included in the standard setup as the software would not return any error message as well in interactive mode. Contact deeplines@principia.fr for more details.

  • Path to FE solver executable file: The path to the finite elements solver executable file must be defined prior to running any analysis from the GUI. This path has been defined once for all within the Settings menu within previous Versions. You may now set different paths for different DSK model files, which allows to run set of analyses with a previous or customized Version of the FE solver when needed.

Lines

  • Winch line component: A new Winch line component has been added which allows to model cables being paid in or paid-out. Winch lines may be created by selecting the New Line button and further selecting Winch Line type from associated drop-down menu. Winch lines are very similar to Generic Lines though they include a new Winch tab in which you may specify how the reference length of the Winch Line is to be varied as a function of time or quasi-static steps. The length of every bar or beam elements composing the Winch line will be varied as desired during the simulation. Such lines are of course submitted to hydrodynamic loads arising from current and waves.

  • Jacket-like meshes: External meshes composed of line elements can now be imported from the Drawing tabs of Rigid Bodies and Generic Floaters. These meshes may be used to represent assemblies of lines such as jackets or any truss structure. Meshes have to be defined in special formatted text files listing nodes coordinates, beam elements, connections between all beams and beams properties such as weight and diameter, which provides an efficient alternative to having to define all these data from the GUI. This feature may for instance be used to find out the hydrostatic equilibrium of jackets when launched from a barge and further simulate U-pending.

  • Unstressed shape of lines: An new option has been added into the Structure tab of Line components to specify whether the unstressed configuration is a straight shape or is as per the as-built shape in the model. The vast majority of pipes shall be considered straight when submitted to no external load. This option is therefore useful to model rigid spools or bents which will keep their initial shape if no external load is applied.

  • Drag/Lift Database: The new Drag/Lift Database is part of Types common properties which can be allocated to Lines. Drag and lift coefficients may now be defined in this database in addition to the Segment types data. Drag coefficients defined in this database may be function of Reynolds number, depth, curvilinear abscissa along Lines, or incidence of the flow with respect to Lines elements as required to derive hydrodynamic loads on non-circular Lines sections. Distributed lift coefficients may also be defined along Lines with non-circular cross-section, as well as added mass and turning moment as required to define complex shapes like wings. Once defined in your database, all these drag/lift properties may then be used within the Lines instead of the standard drag and added mass coefficients by selecting the appropriate option from the Hydrodynamics tab of Lines.

  • Non-isotropic bending stiffness: Bending stiffness of beam elements may be now specified differently for bending about local X-axis and Y-axis. This allow to handle non-circular Lines cross sections. Associated stiffness values may be input from the dialog opened when activating the bi-directional option placed aside the standard bending stiffness in the Flexible segment type dialog.

Environments

  • Environments Sets: A new Environments Set component has been added to the model components to help you defining series of environmental conditions. Each Environment Set may include 3 series of individual wave trains (typically main swell, secondary swell and wind seas), individual current profiles, winds, and offsets. Once all individual components are defined, the list of environments may be defined in a matrix form from the Combination matrix tab. Environments Sets may then be used to easily generate associated Set of Analyses, each analysis being associated with each environment defined in the Environment Set. This new model component will avoid you having to define hundreds of individual wave, current, and offsets components in the Model Browser and will further ease the setup of associated analyses.

  • Wave sets: Wave sets may now include several waves with different headings whereas a single heading previously applied to all individual waves. We have also added the required ratio between maximum expected wave height and significant wave height and seeds for random phases used with irregular waves.

  • Winds: New wind spectra types have been added to model Kaimal and NPD (Norwegian Petroleum Directorate) winds. These new wind spectra types come in addition to existing Harris, Davenport and API wind spectra types.

Other Model Components

  • Ballast component: The Ballast component is a new model component which can be used to model cylindrical ballasts attached to other model components such as Buoys, Floaters and Rigid Bodies. Filling ratio and internal fluid density may be varied if required during quasi-static and time-domain dynamic simulations to simulate various flooding stages of tanks within your analysis. Ballast will results in additional mass and weight applied at the center of volume of the fluid that depends on the instantaneous filling ratio and orientation of the ballast component with respect to the vertical axis. Dynamic fluid motions inside the cylindrical tank such as sloshing are however not taken into account and the position of liquid surface only depends on filling rate and orientation of the ballast.

  • Spring component: A new damping field has been added into the Basic Properties tab of Springs components to simulate dashpots. Resulting viscous damping loads are based on the relative velocity between the end nodes of the Spring element.

  • Flexjoint component: The Flexjoint component is a new model component which allows to link 2 model components through bending and torsion moments depending on the relative orientation of the end nodes of these components. Flexjoint components may be added to your model from the New Link button in the menu bar. Torsion and bending stiffness may be given different values. The bending stiffness may be either constant, multi-linear, or fully non-linear as required to model hysteretic effects. The torsion stiffness may be either constant or multi-linear.

  • Floater non-linear hydrostatics: Hydrostatic restoring loads acting on Floaters during coupled analyses may be either derived from the hydrostatic stiffness matrix read from HDB files or be derived directly from the hulls shape and position with respect to the water line. This latter option allows to handle complex hull shapes with varying draft over the simulation, typically such as small buoys, and accurately derive instantaneous non-linear hydrostatic restoring loads. Non-linear hydrostatics loads are available for Generic Floaters only to which a surfaced mesh may be associated.

  • Connection/Disconnection: A new type of displacement named Dis/Connection is now available in the Imposed Displacement dialog. Dis/Connection displacements allow to change any boundary condition at predefined stages of your quasi-static or time-domain dynamic analysis. This feature may for instance be used to simulate the release of a turret at specified time before determining its global behaviour after the release, or connect any model component to another during the analysis. Additional mass and hydrodynamic coefficients may optionally be attached to the node that was released.

  • Horizontal Displacement: Horizontal displacements may now be defined through their amplitude and direction with respect to X-axis, which avoids having to specify both X and Y components of such displacements.

  • Inertia matrix: A new Inertia Load type is available within the Loads components that allows to define additional inertia terms applied to any model component though associated inertia matrix. Members of the inertia matrix are expressed in the local coordinates system attached to the node. This new Loads type may be created from the Loads panel.

Post-processing

  • X-Y Plots: X-Y plots may now be displayed in the standard post-processing window, both X and Y axes being associated with different results variables.

  • DNV code checks: DNV OS F101 and OS F201 code checks are now available in standard post-processing for dynamic analyses. These code checks comply with the last edition of DNV offshore standards. The acceptance criteria for combined loading is automatically derived considering functional loads (derived from pure static solution), static environmental loads (derived from the last step of the quasi-static analysis) and dynamic environmental loads (derived from the dynamic analysis). These code checks are available both for ALS and ULS. Parameters for high, normal and low safety class may also be tuned if required from the main Settings menu.

  • New results variables: New results variables have been added to standard post-processing, such as internal pressure, external pressure, DNV 1981 equivalent stress and DNV RP C203 stress members, bending strain, combined axial and bending strain. Von Mises equivalent stress may now be built considering SCF and corrosion thickness allowance instead of being based on the stress components for plain metal. Built-in angles (i.e. angular deflection between a Line and the theoretical departure angle defined within the component to which the line connects) may also be extracted away from connection points.

  • Display of non-converged solutions: Non-converged solutions may now be saved and displayed in the 3D View window once your analysis is completed. This allows to check how the Lines and other model components move when the solver is looking for the static solution, and identify potential numerical oscillations when the static analysis fails to converge. You may ask for the solver to save non-converged solutions by activating the option labelled Save non-converged solutions from the Advanced parameters dialog associated with the Calculation Parameters for static analyses.

  • Improvements to fatigue analysis: All fatigue analysis dialogs have been redesigned to ease the definition of fatigue post-processing.
    Each fatigue analysis now includes several tabs : General parameters tab (type of analysis, the calculation method, the type of lines and the saving parameters), Load cases tab (scatter diagrams and definition of tension or stress RAO), Stress components tab (type of stress to be calculated for rigid pipes), and Lines sections tab (definition of lines sections along the damage is to be derived, S/N or T/N curves).
    Scatter diagrams may now be defined directly from the GUI in dedicated grids in addition or replacement to existing external text files. Fatigue analyses may also be performed for bounded flexible hoses when required through the use of special formatted databases used to convert global strain into local stress in each steel component.

  • Updated S/N curves library: Fatigue S/N curves from DNV provided in the .CSN library file have been revised in accordance with DNV RP C203 2008 Edition. This resulted in changes for S/N curves in seawater with cathodic protection B1 and B2.

  • Zones Study post-processing: The Zones Study post-processing has been improved with new results variables, updated presentation of results and easier export to Excel facility. New results variables for Extreme cases include axial and bending stress for rigid pipes, whereas new results for Cyclic load cases now offers various combinations based on maximum curvature, maximum built-in angle, maximum amplitude of plane curvature or built-in angle. In addition to these new variables, all results may be exported to Excel with a single click. Last, in addition to time-domain dynamic analyses, the Zones Study module may also post-process results from dynamic analyses carried out in the frequency-domain.

  • Export to Excel: All graphs displayed in DSS results files may be exported to Excel as previously. Presentation of tabs in the Excel file has been improved with two new tabs. The new List of Plots tab shows the complete list of graphs included in the Excel file, together with short description of the graph and hypertext link to associated tabs showing the graph. Hypertext links to this List of Plots tab have also been added to all tabs with numerical values to easily get back to the first tab. The new Statistics tab includes a table with minimum and maximum numerical values automatically extracted from each graph.

  • Batch post-processing: Batch post-processing is still based on external script files through the format of these files has been improved and now allow automated post-processing of multiple analyses based on the same script file. Instead of having a single DSS file name placed in the header of each script file, you may now list several analyses on which the post-processing instructions are to be performed.

  • Stress concentration factors: SCF values may still be defined from the Rigid Pipe segment type. You may now specify either a single SCF value as previously or define SCF differently for axial and bending stress components. These factors could also be used for fatigue analyses or be changed from the Fatigue Analysis dialog to easily carry out sensitivity analyses on this parameter.

  • Saving of graph parameters: Graph parameters such as zoom ratio, colour, etc. were not correctly saved in DSS results files and the parameters of each graph was automatically reset when the graph displayed. This has been modified and all graph parameters are now properly saved for every graphs.

Improvements to FE solver

  • Dynamic wake (solver only): A dynamic wake model can be use to compute interferences in riser array. The model may be based on Huse or Blevins formulations.

  • Low frequency floater yaw damping (solver only): You may now include the effect of viscous damping on the floater yaw motions. Modelling yaw damping effects is especially useful for low frequency motion simulations. The formulation is based on B. Molins PhD Thesis entitled Un modle de comportment des navires amarrs sur un point unique, 1981.

  • Drag coefficient in air (solver only): Lines made of bar or beam elements may now be submitted to wind loads through specific drag coefficients. Wind loads will be derived when a Wind component is included in the analysis from the relative wind and line velocity. Both axial and normal drag coefficients may be defined. Wind loads shall of course apply on Lines section above the water line. See associated *BARCAIR, *BEAMCAIR and *PHYS keywords for details.

  • Concentrated loads input external through files (solver only): This new feature comes in addition to time-dependent external loads that can be defined from the GUI within Loads components. You may now use as an alternative time-history of external loads defined in a text file with the *FLOAD keyword.

  • Bounded iterative displacements (solver only): Iterative displacements used to find out the converged solution may be bounded to limit potential numerical oscillations by setting appropriates bound values in the Calculation Parameters dialog. New fields have been added to associated *DELTAX keyword which allow to set different bound values for static and time-domain dynamic analyses.

Bug fixes

  • Connection of Rigid Bodies: Rigid Bodies components can now be connected together.

  • Selection of Motion RAO: Selection of motion RAO to be used for dynamic analyses is now based on the relative heading between the wave and the Floater at initial time of the dynamic analysis. This ensure that consistent RAO data are used even when the heading is changed through the static analysis.

  • Predefined results in Analyses Sets: Selection of Predefined results associated with newly created Analysis Set might sometimes be impossible until the list of analyses was fully generated, as the list of model components displayed to define your post-processing queries was not automatically updated. This bug has been fixed and all model components can now be selected to define predefined results in Analyses Sets without any restriction.

  • Rain-flow damage counting without wave: Fatigue analyses based on rain-flow damage counting procedure were unable to proceed in case no wave was present in the dynamic analysis. The rain-flow method may now apply to any dynamic analysis without waves.