1. OrcaFlex User Group 2003 www.orcina.com Slide 1 of 8 OrcaFlex - Modelling Contact Clearance Models Seabed clearance (from line centreline at a node) Line clearance (between segment centrelines) Line contact clearance (between segment outer surfaces) Clearance may be all you need if contact is forbidden Use dummy lines to mark “no-go” areas like moonpool edges

2. OrcaFlex User Group 2003 www.orcina.com Slide 2 of 8 OrcaFlex - Modelling Contact Contact Models Seabed contact (with line centreline at a node) Solid contact (with line centreline at a node) Line clash contact (between segment outer surfaces) All linear elastic + linear damping (inward motion only)

3. OrcaFlex User Group 2003 www.orcina.com Slide 3 of 8 OrcaFlex - Modelling Contact Contact Example - #1 Roll-on/roll-off contact over an arch using solids Slowly varying contact – contact force is insensitive to contact stiffness and is therefore reliable Fine segmentation needed in contact region Small changes can give different static solutions

4. OrcaFlex User Group 2003 www.orcina.com Slide 4 of 8 OrcaFlex - Modelling Contact Contact Example - #2 Sliding contact – riser guide modelled using a hollow solid Contact occurs at centreline – hole represents “rattle space” High solid stiffness gives a lot of rattling contact; lower stiffness is more realistic Riser rests first on one side then the other – contact force is a representative result

5. OrcaFlex User Group 2003 www.orcina.com Slide 5 of 8 OrcaFlex - Modelling Contact Contact Example - #3 Sliding contact – riser guide modelled using line clashing Contact occurs at segment OD – guide line spacing chosen to give the same rattle space as before High contact stiffness needed to prevent one line cutting through another Force results similar to previous model OrcaFlex 8.4 will include a new Clash report

6. OrcaFlex User Group 2003 www.orcina.com Slide 6 of 8 OrcaFlex - Modelling Contact Contact Example - #4 Dynamic clashing between risers – hammer/anvil example 2 versions – 5m and 2m segments How to characterise the initial impact – force, impulse, energy…? Use of clash report to determine impact sequence, then time histories for closer investigation

7. OrcaFlex User Group 2003 www.orcina.com Slide 7 of 8 OrcaFlex - Modelling Contact Contact Example - #5 More complex example – re-entry of a releasable buoy to an FPSO Ship structure represented as a network of lines Buoy represented as a single fat line for clash purposes Shows a series of rattling impacts during re- entry

8. OrcaFlex User Group 2003 www.orcina.com Slide 8 of 8 OrcaFlex - Modelling Contact Contact Example - #6 Using links to model contact – example from OrcaLay Applicable where contact point is predictable with no slip Long links avoid small errors due to axial movement (strain) of pipe Solids (Shapes) used for illustration only – zero stiffness