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Basics Case studies Conclusions
OpenFOAM and the �ap
P.Schmitt1 K. Doherty 2
1Queens University Belfast, Belfast, United Kingdom
2Aquamarine Power Ltd, Edinburgh, United Kingdom
23rd January 2013, Maynooth
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Basics Case studies Conclusions
Outline
1 Basics
2 Case studies
3 Conclusions
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Basics Case studies Conclusions
Computational Fluid Dynamics
Characteristics
Fully viscous, non linear simulation of free surface �ows
Reynolds-averaged Navier�Stokes equations
Overhead with pre and postprocessing
computing time/ HPC facilities
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Basics Case studies Conclusions
CFD - Challenges
Turbulence modeling
Relevant scales
Mesh motion
Automatized and e�cient mesh generation
transient simulations
wave maker and beaches
solver tuning
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Basics Case studies Conclusions
CFD - Moving bodies
Updating positionof body
Mesh motion
Mesh
deformation
Sliding
interfaces
Topology
changes
Overlapping
meshes
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Basics Case studies Conclusions
CFD - Moving bodies
Updating positionof body
Mesh motion
Mesh
deformation
Sliding
interfaces
Topology
changes
Overlapping
meshes
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Basics Case studies Conclusions
CFD - Moving bodies
Updating positionof body
Mesh motion
Mesh
deformation
Sliding
interfaces
Topology
changes
Overlapping
meshes
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Basics Case studies Conclusions
CFD - Moving bodies
Updating positionof body
Mesh motion
Mesh
deformation
Sliding
interfaces
Topology
changes
Overlapping
meshes
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Basics Case studies Conclusions
Outline
1 Basics
2 Case studies
3 Conclusions
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Basics Case studies Conclusions
Example case
25th scale tank model
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Basics Case studies Conclusions
25th scale tank model
Mesh generation: 30 min
Runtime: 24h on 64 cores
-40
-30
-20
-10
0
10
20
30
40
0 2 4 6 8 10
Rotationangle[deg]
Time [s]
CFDExp
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Basics Case studies Conclusions
25th scale tank model
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Basics Case studies Conclusions
25th scale tank model
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Basics Case studies Conclusions
25th scale tank model
-10
-5
0
5
10
15
20
25
15 15.5 16 16.5 17 17.5 18 18.5 19
Rotationangle[deg]
Time [s]
ExpCFD
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Basics Case studies Conclusions
Detailed design of a WEC
Obtaining statistically signi�cant data
20-50 seastates for 20-30 min time (full scale)
Response of Power Take o� (PTO)
directional heading
water-level
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Basics Case studies Conclusions
Cost
24 hours
Tank testing: 144− 288 sea states/PTO conditionsCFD: 2.7$/8node/hour ⇒ 74650− 149300$
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Basics Case studies Conclusions
Cost
24 hours
Tank testing: 144− 288 sea states/PTO conditionsCFD: 2.7$/8node/hour ⇒ 74650− 149300$
For obtaining statistically relevant data CFD will not replace tanktesting for many years!
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Basics Case studies Conclusions
Why CFD?
no limitation in tank size and shape
non invasive and easy access to all �eld values like e.g.velocity, pressure
within the limitations of RANS models access to viscous shearforces
Easy and automated variation of any model parameter
and why not?
Time and cost...
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Basics Case studies Conclusions
Shape variation
Gap variation
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Basics Case studies Conclusions
Shape variation
Gap variation
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Basics Case studies Conclusions
Shape variation
Gap variation
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Basics Case studies Conclusions
Shape variation
Gap variation
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Basics Case studies Conclusions
Shape variation
Gap variation
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Basics Case studies Conclusions
Rotation Angle
-15
-10
-5
0
5
10
15
20
0 1 2 3 4 5 6 7 8
Rotationangle[deg]
Time [s]
nogapsmall
mediumlargeopen
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Basics Case studies Conclusions
Moment
-40
-30
-20
-10
0
10
20
30
0 0.5 1 1.5 2 2.5 3 3.5
Mom
ent[Nm]
Time [s]
nogapsmall
mediumlargeopen
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Basics Case studies Conclusions
Power Output
-100
-80
-60
-40
-20
0
0 20 40 60 80 100
Lossof
Pow
er[%
]
Gapsize [%]
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Basics Case studies Conclusions
Blockage e�ect
In�uence of tank width
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Basics Case studies Conclusions
Blockage e�ect
In�uence of tank width
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Basics Case studies Conclusions
Blockage e�ect
In�uence of tank width
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Basics Case studies Conclusions
Blockage e�ect
Velocity beside the �ap
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Basics Case studies Conclusions
Blockage e�ect
Velocity beside the �ap
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Basics Case studies Conclusions
Blockage e�ect
Velocity beside the �ap
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Basics Case studies Conclusions
Blockage e�ect
Velocity beside the �ap
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Basics Case studies Conclusions
Blockage e�ect
Velocity beside the �ap
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Basics Case studies Conclusions
Blockage e�ect
Velocity beside the �ap
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Basics Case studies Conclusions
Blockage e�ect
Velocity beside the �ap
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Basics Case studies Conclusions
Blockage e�ect
Velocity beside the �ap
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Basics Case studies Conclusions
Blockage e�ect
Velocity beside the �ap
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Basics Case studies Conclusions
Blockage e�ect
Velocity beside the �ap
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Basics Case studies Conclusions
Rotation
-10
-5
0
5
10
15
20
25
0 2 4 6 8 10
Rotationangle[deg]
Time [s]
2.3m4.6m5.5m
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Basics Case studies Conclusions
Impact I
Figure: Surface elevation in front of the �ap before and during impact
event.
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Basics Case studies Conclusions
Impact I
Figure: Surface elevation in front of the �ap before and during impact
event.
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Basics Case studies Conclusions
Impact I
Figure: Surface elevation in front of the �ap before and during impact
event.
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Basics Case studies Conclusions
Impact I
Figure: Surface elevation in front of the �ap before and during impact
event.
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Basics Case studies Conclusions
Impact I
Figure: Surface elevation in front of the �ap before and during impact
event.
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Basics Case studies Conclusions
Impact I
Figure: Surface elevation in front of the �ap before and during impact
event.
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Basics Case studies Conclusions
Impact I
Figure: Surface elevation in front of the �ap before and during impact
event.
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Basics Case studies Conclusions
Impact I
Figure: Surface elevation in front of the �ap before and during impact
event.
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Basics Case studies Conclusions
Impact I
Figure: Surface elevation in front of the �ap before and during impact
event.
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Basics Case studies Conclusions
Impact I
Figure: Surface elevation in front of the �ap before and during impact
event.
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Basics Case studies Conclusions
Impact II
Figure: Surface elevation in front of the �ap before and during impact
event.
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Basics Case studies Conclusions
Impact II
Figure: Surface elevation in front of the �ap before and during impact
event.
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Basics Case studies Conclusions
Impact II
Figure: Surface elevation in front of the �ap before and during impact
event.
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Basics Case studies Conclusions
Impact II
Figure: Surface elevation in front of the �ap before and during impact
event.
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Basics Case studies Conclusions
Impact II
Figure: Surface elevation in front of the �ap before and during impact
event.
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Basics Case studies Conclusions
Impact II
Figure: Surface elevation in front of the �ap before and during impact
event.
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Basics Case studies Conclusions
Impact II
Figure: Surface elevation in front of the �ap before and during impact
event.
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Basics Case studies Conclusions
Impact II
Figure: Surface elevation in front of the �ap before and during impact
event.
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Basics Case studies Conclusions
Impact II
Figure: Surface elevation in front of the �ap before and during impact
event.
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Basics Case studies Conclusions
Impact II
Figure: Surface elevation in front of the �ap before and during impact
event.
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Basics Case studies Conclusions
Shape Variation
Figure: Original design and variations.
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Basics Case studies Conclusions
Shape Variation
Figure: Original design and variations.
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Basics Case studies Conclusions
Shape Variation
Figure: Original design and variations.
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Basics Case studies Conclusions
Shape Variation
Figure: Original design and variations.
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Basics Case studies Conclusions
Shape Variation
Figure: Original design and variations.
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Basics Case studies Conclusions
Shape Variation
Figure: Original design and variations.
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Basics Case studies Conclusions
Flow �eld
Figure: Flow �eld around shape variations.
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Basics Case studies Conclusions
Flow �eld
Figure: Flow �eld around shape variations.
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Basics Case studies Conclusions
Flow �eld
Figure: Flow �eld around shape variations.
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Basics Case studies Conclusions
Flow �eld
Figure: Flow �eld around shape variations.
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Basics Case studies Conclusions
Conclusions and Outlook
Conclusions
CFD still too expensive to create statistically relevant data
CFD complements experimental tests
Shape variations
Understanding experimental limits
Access to all �eld variables
Viscous e�ects