1. FluidEarth 2 Launch Meeting Linking Area Type Time Stepping Models (An Overview)
HR Wallingford, 18th April 2013
Dr David M Kelly

2. What are ‘Area Models’? Overview The OTT2D and Exner models
Creating components
The need to adapt
An example of a simple ‘Adapter’
One- and two-way coupling
Representative results for a composition with one-way coupling
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3. What are area models?
Two-dimensional horizontal type models where values of dependent variables are typically computed on an underlying Eulerian mesh
Examples include: SWAN, TELEMAC 2D or 3D, Sisyphe and …
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4. OTT2D and Exner OTT2D: 2DH FVM NLSWE solver (cell-centred)
EXNER: 2DH FD sediment continuity equation solver (node-centred)
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5. Creating the Components
Straightforward:
Create a (new) engine dll and a dll for the (modified) original code – typically FORTRAN
A template (subroutines) for the Engine is available in FORTRAN
Original model will need to be modified to remove time-stepping procedure (loop) converted from program to subroutine
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6. Why we need to adapt
As well as exchanging information in time the we may need to exchange info in space:
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7. Simple Adapter
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8. Simple Adapter
The triangle containing the point is located employing an ‘inpoly’ type algorithm:
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9. Simple Adapter
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10. One and two-way coupling
One way coupling – For water sediment simulations this is often unstable
Two way coupling – (Morphodynamic) time-stepping requires thought
OTT2D
EXNER A
OTT2D A
EXNER A
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11. The Composition – Test Case
Nested Mesh System
IC simple wet-wet dam-break
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12. The Composition – Pipistrelle GUI
Setting Up the Variable Transfers:
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13. The Composition – Pipistrelle GUI
New Adapted Output:
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14. The Composition - Results
Flow Snapshot
one way coupling
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15. Conclusions
Two Area Models have been successfully coupled with the new frame work using a spatial-type adapter
Coupling is intuitive once you have familiarised yourself with the template to construct an engine (removing time-stepping from your own code should be straightforward)
It is possible to create ‘stand-alone’ version of compositions that can be run in Visual Studio – very useful for debugging
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16.
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