GeniE : Shell Modelling, Status and Directions

Ole Jan Nekstad, Sesam Product Manager, DNV Software1 September 2011

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SesamTM

40 years of success

GeniE – Shell modelling, status and directions

Presenter

Presentation Notes

Alternative title slide

© Det Norske Veritas AS. All rights reserved.

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Shell modelling - status


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Shell modelling functionality 4 main options – they are all based on curves

Skin/loft

Cover

Curve net interpolation

Extrude


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Skin / loft curves Usually works fine with all types of curves

- If not, a trick may be to rebuild the curves with the same number of points

May get gaps between adjacent shells in the cross direction of the skinning direction

Workaround is to use a model curve from adjacent shell in further modelling

Gap, elements don’t share the same nodes


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Use existing shell edge (model curve) Use model curve of shell edge to ensure topological congruency

May skin/loft, cover or net interpolate adjacent shell, as long as the model curve is used- Trimming of curves required?


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Curve net interpolation Use net of interior and/or boundary curves

- Does not require trimming of curves- Requires common intersection points

OK


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Internal edges Composite curves may give internal edges

- Same issue with skin/loft- Use global meshing rule Remove internal edges


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Conclusion

Preferred approach:

Use polycurves and curve net interpolation

Need common intersection points


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New features for shell modelling in GeniE v5.3-10 released April 2011


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Why enhancements to existing modelling capabilities

Models like this can be created today.

We have identified potential user efficiency gainswithin local modelling details and flat surface modelling


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Easier modelling of planar surfaces Create closed surfaces by single click using flat region feature

- Intuitive and simple to use.- Bounding by existing plates, beams and guide curves- No need to split lines

Insert Plate Flat Region to position cut-plane

Plates, beams and curves in cut-plane

Click inside area.Uses visible model

Presenter

Presentation Notes

Read the text: GeniE has been used for quite a while to model complex surfaces. Based on the feedback from users we have included new modelling capabilities that will speed up modelling. In some cases 3 to 5 user operations before is now replaced by 1 user operation. This will obviously help reducing modelling time. The new features include a much more powerful copy or move operation as a vector can be used directly together with a length specification. Another important new functionality is the flat-region tool that allows the user to easily insert plates between any surrounding structure or guide lines like for example inside the web-frames in a vessel. The example above shows a cut-plane inserted at a random position and the individual plates are inserted simply by graphic clicking. This used to be several user operations per plate before, while it now is reduced to how many plates need to be inserted. Start the top video and use the text (duration 52 seconds): 0 sec: This video shows how the flat region modelling functionality is used to define individual plates when there are continuous guide lines that are common for many plates. 15 sec: A temporarily flat region is defined for elevation z at 0 meters. When viewing this in 2D it is possible to generate a plate simply by clicking in the area defined by surrounding guide lines. Please notice that the guide lines as common for several areas. This was not possible before as it was necessary to split the guidelines so that they were unique per plate. Start the bottom video and use the text (duration 1 minute and 28 seconds): 0 sec: This video shows how the flat region modelling tool can be used when the boundaries are determined by existing structure or a mix between structure and guidelines. 10 sec: A temporarily cut plane is defined at elevation z equals minus 1 meter. When viewing in 2D we clearly see the guidelines as defined by the existing structure and two guide circles that were defined as guide curves. When clicking on the area the plate is defined. Please notice that GeniE keeps control of what is outside and inside the guide lines. Therefore in this case the area inside the circles is not included as part of the plate. 50 sec: By doing the same again, but at elevation z equals minus 2 meters we can define the plates inside the guide circles simply by clicking inside the circle area. 1 min 10 sec: Finally this example shows how to fill the entire web-frame if there are no guiding lines present. The elevation in this case is z equals minus 4 meters and the web-frame plate is inserted by clicking in the area as defined by the surrounding longitudinal structure.


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Vector from other object- local beam system- plate normal- 3-point plane normal, etc

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Additional options in vector selection dialog


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Additional options in snap plane and divide dialogs Plane defined by three points

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More features for making geometry Scaling and offsetting of curves and surfaces makes it easier to make regular as

well as complex geometrical shapes- Scaling around a point is often used to create similar shapes for the purpose of making

structure and controlling finite element mesh, Edit Copy- Offsetting will create similar shape (line or surface) in a given distance

Presenter

Presentation Notes

Read the text: Other important new functions are the ability to do both scaling and offsetting will help both quick modelling as well as better ways of controlling the mesh in critical parts. The scaling is available from the Edit Copy functionality, while the offset is accessed by right clicking the line or surface. Start the top video and use the text (duration 3 minutes and 20 seconds): 0 sec: This video shows how to do scaling of different shapes defined by guide curves and how this can be used to control the finite element mesh. 10 sec: The triangle is selected and a scaling factor of 1.5 is used. The reference point for the scaling is the bounding box center. This point is automatically found by GeniE. 35 sec: The quadrant is selected and a scaling factor of 2 is used. In this case a user defined point is used as the reference point 1 min 2 sec: The circle is selected and a scaling factor of 1.5 is used together with the bounding box as reference point. 1 min 30 sec: The two circles are used as boundaries for making a plate using the plate cover functionality 1 min 45 sec: The plate is divided into two to be able to insert feature edges for the purpose of controlling the mesh along the edges. The feature edges are inserted by referring to the connectivity lines. The connectivity lines are found when double clicking a plate. 2 min 25 sec: The same number of elements is used for all feature edges to ensure a regular mesh around the hole. In this case there are 16 elements with the same length along a feature edge. 3 min 5 sec: A regular mesh is now created using the other default mesh options in GeniE. As can be seen, the quality of the mesh is very good according to the relative Jacobi determinant. Start the bottom video and use the text (duration 1 minute): 0 sec: This video shows how tom offset two different curves and how to create plates based on a cover operation 5 sec: A curve or surface can be offset by right clicking and selecting the option Offset. In this case an offset of minus 1 meter is selected. Please notice that the offset is always perpendicular to the original line or surface. This means that a straight line cannot be offset since it is not possible for GeniE to determine the in-line plane. 22 sec: The scone curve is offset with a offset value of 1 meter. 40 sec: The original and offset curves are now used as boundaries when making plates using the cover curve functionality


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Meshing improvements Separated handling of mesh and loads use less peak memory

Conditional Regenerate Mesh- For large models, significant performance improvements are achieved when updating

analysis models- Does not have to regenerate mesh if only properties

or loads are changed. FEM file is updated instead.- Topology and mesh rule changes force new mesh

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Ongoing modelling activities


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Ongoing activities 64-bit version of GeniE – tentatively release date September 2011

- Performance improvements, “unlimited” memory available – important for large models (e.g. global FPSO model)

- ISO Joint Check “critical” joints, the option to compute “Ub from run” is now available- Sacs Import : Result combinations read into GeniE- Frame code checks : Results stored on HDF5 files, reducing chance of running out of

virtual memory


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Ongoing activities – scheduled for release Q1/2012 Additional ways for modelling of guiding points and curves

Common representation of all curves using NURBS

Pictures from prototype implementation


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Ongoing activities – some examples E.g. Different type of line representations

Classic cubic spline interpolation

G1 curve, consisting of linear and cubic segments, which

interpolates the given points

Polynomial line. Shape decided by

control points, but no interpolation

Shape-preserving interpolating spline

Guide Spline Poly Curve Bezier Curve S/P Spline Curve


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Ongoing activities – some examples Bezier curve and control points – shape preserving curves

- Gives the user much more flexibility in creating almost any curve

Three control points Four control points –the middle point is used twice

Four control points


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Ongoing activities – scheduled for release Q1/2012 New DXF import using the

Rhinoceros plug-in

Poly-lines supported with new NURBS implementations

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Our biggest challenge when importing line data Real case example – importing data from NAPA

All looks fine!

But often lines do not intersect


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Ongoing activities – scheduled for release Q1/2012 Mapping of one set of curves onto another

set, e.g. buttocks onto station curves/offset table- GeniE will propose a cleaning of non-matching

lines- User to decide which line to “move” to achieve

matching lines

All lines are matching

Two lines are not matching


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GeniE : Shell Modelling, Status and Directions