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Hydrodynamic application for standard DTMB 5415 bare hull
with OpenFOAM
A. Penza SCAI Department, CINECA
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Contents A. anteFoam: who I am – why I am here
B. Validation of interFoam solver
1. DTMB5415: a standard hull 2. Material and Methods 3. OpenFOAM VS Gold-Standard comparisons 4. OF scalability test 5. Conclusions
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“anteFoam”
Ø Who I am: aerodynamic engineer graduated @ PoliMi in April 2012
Ø 12 months internship (begin: 01/07/12) at CINECA in collaboration with Luna Rossa Challenge to investigate the usability of OpenFOAM in marine CFD
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Picasso Ø Where we started: my first crash case
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DTMB 5415: a standard hull in marine CFD Ø Standard study to validate
marine CFD analysis. Ø Bibliography references:
• L. Larsson, F. Stern, M. Vissonneau, “CFD in ship Hydrodynamics”
• Y. M. Ahmed, “Numerical simulation for the free surface flow around a complex ship hull form at different Froude numbers ”
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CFD model 1. Solver:
Ø Multiphase flow (water/air) Ø Volume Of Fluid method employed Ø 0 D.O.F. (captive-case) Ø Unsteady case
In OpenFOAM we got the interFoam solver 2. BC settings:
Constant pressure patch
Slip wall Velocity inflow
patch
No slip wall on boat surface
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CFD comparisons 1. Qualitative:
Ø Iso-surface of computed mass-fraction Ø Pressure on hull surface Information about wave shape, flow separation, stress distribution on hull
2. Quantitative: Ø Pressure drag Ø Viscous drag
My comparison is: OF vs GS (numerical)
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DTMB 5415: computational mesh
Ø Particular refinement in the free surface region is crucial
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CFD results Ø Convergence reached in 10 s
Ø OpenFOAM vs Gold-Standard Drag values :
• FxP: -0.34 % • FxV: -4.95 %
Ø Quite good agreement of results
GS GS
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Froude sensitivity • Froude number:
• At differnt Froude: different behaviours
• Froude range of interest for DTMB hull: 0.38 – 0.55
Ø @ Fr = 0.38: convergence
reached in approximately 20000 iterations
Ø @ Fr = 0.55: convergence reached in approximately 30000 iterations
GS GS
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Ø Coerent drag trend in agreement with increasing Froude number, as expected
Froude sensitivity
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OpenFOAM vs Gold-standard results Ø Mass fraction visualized on hull surface: wave shape detected
Ø Excellent agreement with Gold-Standard results OF GS
OF
GS
OF
GS
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Velocity field
Ø Symmetry well caught by the solver in the velocity field computations
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Pressure field on hull
a) Zero pressure distribution well caught b) Zero pressure transom well caught c) Bulb pressure distribution to be further investigated
a) b)
c)
OF GS
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Free surface and pressure field
Free-surface: iso-surface mass fracion α= 0.5
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Ø Wave height visualized on 3D air/water interface surface (mass fraction 0.5)
Ø Cone of influence identified: physical angle detected, in agreement with theory
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Half-hull simulations
Ø save 43.5% computational time
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• Formule scalability:
- Speed-up: - Efficiency:
• Super-linearity behaviour observed: cache effect
Scalability tests
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Machine details OpenFOAM v2.1.0 - v2.1.1 (latest release)
on cluster Lagrange @ CINECA – Segrate (MI)
• 336 nodes BL460c & BL2x220 • 3200 cores Intel X5472 & X5660 • 6400 GB RAM • 30 TB disk (EVA4400 + MSA1500) • Infiniband QDR/DDR Voltaire
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Conclusions
Ø OF works well for marine studies
Ø Time consumption makes feasible also for industrial design
Ø HPC capabilities can be exploited
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Aknoledments • G. Provinciali Luna Rossa Challenge 2013 • A. Vergombello Luna Rossa Challenge 2013
• R. Biscontini Luna Rossa Challenge 2013 • R. Ponzini CINECA – SCAI Department
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Thank you for your attention
Questions?
