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Copy of Application of the CFD Solver FLUENT to Keels of Sailing Yachts

Master Thesis Presentation, Jouke de Baar, June 18, 2010, TU Delft
by

Lakshmi Balakrishnan

on 8 July 2013

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Transcript of Copy of Application of the CFD Solver FLUENT to Keels of Sailing Yachts

Application of the CFD Solver FLUENT to Keels of Sailing Yachts
Jouke de Baar
June 18, 2010
TU Delft
Method
Validation
SWOT
Implications
Conclusions
What?
Why?
FLUENT can give reliable keel and hull drag estimates

Keel drag can be scaled with form factor method

Keel drag might best be scaled with a flat plate
skin friction line

Keel rudder interaction is Froude scaled
Reynold's Averaged Navier Stokes

Realizable k-epsilon turbulence model

Wall treatment

Volume of fluid (VOF) method

Structured grid

Richardson extrapolation
All ready present in the selected experiments:
Towing tank limits the domain
No heel or leeway
No incoming waves
Etc.

Additional in the simulation:
Incompressible flow
Perfectly smooth hull and keel
Etc.
Keel 1
Keel 3
Why use realizable k-epsilon turbulence model?

The experiment is fully turbulent due to turbulence stimulation strips

The blunt trailing edge of the keel is likely to exhibit separation and recirculation






If CFD gives reliable estimates:

It reveals details and mechanisms that often remain unseen in the experiments

In the future it might become faster and cheaper than experiments


Elements Result Extrapolation
1 2.00 (2.00)
2 2.83 (3.10)
4 3.06 3.14
... ... ...
32 3.14 3.14

p = 1.89

GCI ratio = 0.93

cd = 0.0055 ± 0.0006

cd = 0.0057 (experiment)
Example (Bare Hull)
Structured grids
Grid convergence study
Error estimate

Amount of validation data
Improved grid generation
Parrallel & machine improvements
Turnover time
Free-surface distortion
Coarse grids (high growth etc.)
Bias
Unjustified confidence
Strengths
Weaknesses
Opportunities
Threats
Scaling Keel Drag
Simplifications
Keel Rudder Interaction
Scaling Keel Drag
Discretization
Froude scaling
Reynold's scaling?
Direct measurement of experimental hull and keel drag (Keuning, 2006)
Validation for:

Bare hull
Hull and Keel 1
Hull and Keel 3 - blind


Four out of five drag coefficients
are within simulation error

All estimates are within 10%
CFD
Conservation of Mass
(Cons. of Momentum)
Grid Refinement


The experiment is fully turbulent due to turbulence stimulation strips

The blunt trailing edge of the keel is likely to exhibit separation and recirculation








The experiment is fully turbulent due to turbulence stimulation strips

The blunt trailing edge of the keel is likely to exhibit separation and recirculation






C = C + (1+k) C
Ship



Flat plate
Constant ratio?
T Res F
Full transcript