j. craig mudge ee380 stanford university 2/19/2003 1 computer technology in america’s cup yacht...
TRANSCRIPT
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1J. Craig Mudge ee380 Stanford University 2/19/2003
Computer technology in America’s Cup
Yacht Racing
Dr. J. Craig Mudge
Pacific Challenge
ee380 Colloquium
Computer Systems Laboratory
Stanford University
Feb 19, 2003www.pacific-challenge.com
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2J. Craig Mudge ee380 Stanford University 2/19/2003
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3J. Craig Mudge ee380 Stanford University 2/19/2003
6 legs in America’s Cup course
Time
Min:sec
Delta in
seconds
Start 0
1 26:11 12
2 24:14 -34
3 26:37 -26
4 22:43 -14
5 27:33 -26
finish 25:43 7
Alinghi Race 2:-
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4J. Craig Mudge ee380 Stanford University 2/19/2003
How a sailboat moves ahead
• Downwind– Push on sails
• Upwind – Lift from sails– Lift from keel
• Context – Changes in wind strength and direction– Changes in wave shape, direction, and frequency
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5J. Craig Mudge ee380 Stanford University 2/19/2003
Defender vs Challenger
Video clips of last couple of days racing - what to watch for
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6J. Craig Mudge ee380 Stanford University 2/19/2003
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7J. Craig Mudge ee380 Stanford University 2/19/2003
Elementary theory
Leeway angle
Aerodynamic forces from sails
hydrodynamic
Lift dragLift drag (or resistance)
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8J. Craig Mudge ee380 Stanford University 2/19/2003
Tacking up wind
The boat that sails at an angle “closer to the wind”gets upwind faster
Wind directionZig-zagging up wind towards our destination
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9J. Craig Mudge ee380 Stanford University 2/19/2003
Polar representations of boat speed
20
5
10
Radial representation of Boat speed at different true wind angles for one windspeed
(Adapted from 12 metre designed by S Killing)
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10J. Craig Mudge ee380 Stanford University 2/19/2003
A list of computer usesArea Type
Design of hull Hydrodynamic modeling (to reduce drag)
Hull appendages Hydrodynamic modeling (lift and drag)
Design of sails Aerodynamic modeling; photogrammatic
Computational Fluid Dynamics (CFD)
Modeling, analysis, and visualization – sails, hulls, appendages
Two boat testing Data collection and data management
Navigation/tactics/ strategy
Performance parameters; predictions for next leg
Campaign Project/financial management, travel, web site
Weather Forecast wind patterns for each race
Sports media Visualization of race course from telemetry
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11J. Craig Mudge ee380 Stanford University 2/19/2003
AcknowledgementsJim Antrim, naval architect
Richard Burton, sailor and computer scientist
Margot Gerritsen, Computational Fluid Dynamics (CFD) specialist, Stanford Yacht Research
Stan Honey, record-breaking navigator
Olivier Le Diouris, sailor and software engineer
Eric Steinberg, electronics on America True Brian Tramontana, PARC multimedia
* ESPN for video clips* americascup.yahoo.com for photos* Virtual Spectator for screenshots of race course
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12J. Craig Mudge ee380 Stanford University 2/19/2003
Outline
Hull design- both canoe body and appendages
Sail design
Materials - hull and sails
Two-boat tuning
Winning races
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13J. Craig Mudge ee380 Stanford University 2/19/2003
Adding heeling/righting moments to two forces
Leeway angle
Aerodynamic forces from sails
hydrodynamic
Heeling Righting Lift DragLift Drag (or resistance)
AerodynamicHeelingmoment
Hydro-mechanicalRightingmoment
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14J. Craig Mudge ee380 Stanford University 2/19/2003
Lateral stability
Heeling moment from sails
Lead ballast is placed in the lower portion of the keel.
Extreme ballast from bulb (20 tons of a 24 ton IACC boat)
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15J. Craig Mudge ee380 Stanford University 2/19/2003
Alternative to lead bulb for righting moment
Sydney Harbour 18 ft skiffs
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16J. Craig Mudge ee380 Stanford University 2/19/2003
More 18 ft skiffs from Sydney
A very influential design - on modern racing yachts - on latest Olympic class (49er)
Yendys 1924
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17J. Craig Mudge ee380 Stanford University 2/19/2003
Newer IACC boats are much narrower
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18J. Craig Mudge ee380 Stanford University 2/19/2003
Resistance components - upwindup
right Wave
(pushing the water)
Viscous(friction from wetted surface)
heel
ed Added wavesInduced (from leeway)
Heel(extra viscous+wave)
(Fig 5.4, Larsson, 2000)
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19J. Craig Mudge ee380 Stanford University 2/19/2003
Appendages: side force and resistance
Side force (also called Lift)From both keel and rudder
Lift/drag tradeoffAspect ratio
Bulb shape
Turbulence
Tip vortices if depth is limited
End wall not practical, so Winglets used
Winglets also provide lift when boat heeled
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20J. Craig Mudge ee380 Stanford University 2/19/2003
Surface pressure and Streamlines around bulb
From M Sawley (2002) at Switzerland’s EPFL, in Lausanne, an advisor to Alinghi
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21J. Craig Mudge ee380 Stanford University 2/19/2003
An overview of numerical modeling in yacht design
• Fundamental tool is a predictor of performance to compare different designs – Called a VPP (Velocity Prediction Program) -- since early 70s – Given a wind speed and wind angle, a VPP predicts boat
speed, heel, and leeway
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22J. Craig Mudge ee380 Stanford University 2/19/2003
(Milgram, 1998)
Modeling boat speed - VPP
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23J. Craig Mudge ee380 Stanford University 2/19/2003
An overview of numerical modeling in yacht design
• Fundamental tool is a predictor of performance to compare different designs – Called a VPP (Velocity Prediction Program) -- since early
70s – Given a wind speed and wind angle, a VPP predicts boat
speed, heel, and leeway• The balance equations are solved
– Keel lift and side force– Sails lift and drag– Overturning moment
• Modeling these forces in the balance equations is (currently) approximate – Navier Stokes equations (set of differential equations governing the
motion of a fluid) are central part – Models are combination of empirically based and approx of N-S equations
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24J. Craig Mudge ee380 Stanford University 2/19/2003
Overall Hull Design process
1. Decide range of wind strength, sea state
2. Coarse exploration of shapes by numerical modeling, incl CFD
3. Then tank testing
4. Then build one real thing
5. Refine with two-boat testing
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25J. Craig Mudge ee380 Stanford University 2/19/2003
An overview of numerical modeling in yacht design …contd.
Computational Fluid Dynamics (CFD)
RANS (Reynolds-Averaged Navier-Stokes) is a more computationally tractable form of the N-S equations.
In RANS, the flow variables are split into one time-averaged (mean) part, and one turbulent part. The mean values are solved. And the turbulent part is expressed in terms of the mean part.
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26J. Craig Mudge ee380 Stanford University 2/19/2003
An overview of numerical modeling in yacht design …contd.
SGI Origin 3800 128 MIPS R14000 Pc (500Mhz; 64 GB RAM)
Swiss T1 64 DEC Alpha ev6 Pc (500 Mhz; 32GB RAM)
Dell Precision 530 2 Pentium Xeon Pc (1.7 GHz, 2GB RAM)
Largest RANS simulations: 5 million mesh cells: 10 hours on 16 Pc
c.f. AC2000 campaign: 2 million mesh cells: 10 hours on 12 Pc Origin 2000
Typical computer resources are these at EPFL, Lausanne
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27J. Craig Mudge ee380 Stanford University 2/19/2003
Unveiling January 7, 2003 Alinghi
Oracle
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28J. Craig Mudge ee380 Stanford University 2/19/2003
Different winglet configurations and bulb shapes
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29J. Craig Mudge ee380 Stanford University 2/19/2003
Different winglet configurations and bulb shapes
Oracle
Alinghi
Team NZ
(based on photos at the unveiling 1/7/03)
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30J. Craig Mudge ee380 Stanford University 2/19/2003
Universities working in yacht design• University of Auckland• Technical University of Berlin• Chalmers University of Technology• Kiel University• EPFL, Lausanne, Switzerland• MIT• University of Maryland• University of Michigan• University of Southampton• Stanford Yacht Research• Center for Turbulence Research, Stanford
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31J. Craig Mudge ee380 Stanford University 2/19/2003
Outline
Hull design
Sail designMaterials
Two-boat tuning
Winning races
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32J. Craig Mudge ee380 Stanford University 2/19/2003
Positioning and shaping
Crew positions the sails according to required angle of attack
- from polars
Sailors shape the sail using control lines attached to the edge of a sail
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33J. Craig Mudge ee380 Stanford University 2/19/2003
What is the right shape?• Sailmaker designs each sail for a range of
wind strength and wave type. (Sailor selects a sail from the suite, according to expected conditions.)
• Want nice laminar flow, without separation and turbulence
• Lift vs drag curve; polars again
• Both wind tunnels and CFD used
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34J. Craig Mudge ee380 Stanford University 2/19/2003
Vertical characteristics of wind
As we go from deck to top of mast, the wind increases in strength and apparent direction
Has implications for both sail designers and sailors (sail trimming)
8
7
5
Apparent wind is the wind we feel on the boat, as opposed to the true wind.
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35J. Craig Mudge ee380 Stanford University 2/19/2003
Design of downwind sails
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36J. Craig Mudge ee380 Stanford University 2/19/2003
Wind tunnels in sail design University of Auckland Twisted Flow Wind Tunnel
Courtesy U Auckland,Seahorse magazine
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37J. Craig Mudge ee380 Stanford University 2/19/2003
Outline
Hull design
Sail design
Materials - hull, sails, and rigTwo-boat tuning
Winning races
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38J. Craig Mudge ee380 Stanford University 2/19/2003
Ocean racers have to be stronger
Courtesy Richard Bennett
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39J. Craig Mudge ee380 Stanford University 2/19/2003
Forces on rig and hull
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40J. Craig Mudge ee380 Stanford University 2/19/2003
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41J. Craig Mudge ee380 Stanford University 2/19/2003
Prominent logo of sponsor
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42J. Craig Mudge ee380 Stanford University 2/19/2003
OneAustralia 1995
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43J. Craig Mudge ee380 Stanford University 2/19/2003
Older sail material
Courtesy: Mariners’ Museum
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44J. Craig Mudge ee380 Stanford University 2/19/2003
Materials and shapingFlax Cotton Japara silk various polyesters (with or without film) (Kevlar is the best known of the aramid fibers) Carbon
Desired 3D shape in CAD model
Panel shape Mold shape
Sew panels Apply layers (liquid/fiber)
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45J. Craig Mudge ee380 Stanford University 2/19/2003
Improved sail shape with modern materials
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46J. Craig Mudge ee380 Stanford University 2/19/2003
Novel designs
Lexcen keel
Oracle kite
Canting keel
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47J. Craig Mudge ee380 Stanford University 2/19/2003
Ben Lexcen’s winged keel 1983C
ourt
esy:
R
osen
feld
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48J. Craig Mudge ee380 Stanford University 2/19/2003
Oracle kite
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49J. Craig Mudge ee380 Stanford University 2/19/2003
Canting keel and canard
(Reichel-Puch, Dynayacht, 2002)
Wild Oats and Schock 40
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50J. Craig Mudge ee380 Stanford University 2/19/2003
Outline
Hull design
Sail design
Materials
Two-boat tuningWinning races
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51J. Craig Mudge ee380 Stanford University 2/19/2003
Why two-boat tuning
• Shortcomings of numerical modeling and tank testing
• Sensors not accurate enough– A two boat lead at end of a 3 mile leg
requires boat speed 0.7% accuracy; – Accuracy on wind direction, strength also
difficult hard to get accuracy;
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52J. Craig Mudge ee380 Stanford University 2/19/2003
Instruments and data logging on J/105 Kookaburra
Data from instruments:- Wind speed (true and apparent); Boat position; Heading; Boat speed (through water and over the ground); Etc etc
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53J. Craig Mudge ee380 Stanford University 2/19/2003
A leg of a race selected for further analysis
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54J. Craig Mudge ee380 Stanford University 2/19/2003
Log of Wind Oscillations during a race
221º 299º
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55J. Craig Mudge ee380 Stanford University 2/19/2003
Two-boat tuning – Team NZ
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56J. Craig Mudge ee380 Stanford University 2/19/2003
Outline
Hull design
Sail design
Materials
Two-boat tuning
Computer use in America’s Cup races
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57J. Craig Mudge ee380 Stanford University 2/19/2003
Performance
• Performance is a function of– Preparation before the race– Start– Boatspeed
• Design of hull and appendages• Design of sails • Boat handling by crew• Strategy• Tactics• Helmsman’s skill
– Navigation
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58J. Craig Mudge ee380 Stanford University 2/19/2003
Currents Hauraki Gulf, NZ Feb 19
Time: 1400
Courtesy
David Brayshaw, GoFlow
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59J. Craig Mudge ee380 Stanford University 2/19/2003
Currents Hauraki Gulf, NZ Feb 19
Time: 1139Maximum ebb
Courtesy David Brayshaw, GoFlow
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60J. Craig Mudge ee380 Stanford University 2/19/2003
The start
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61J. Craig Mudge ee380 Stanford University 2/19/2003
The start
Display of computed parameterstime to starttime to line tack+acceleration+ travel time (for boat speed, index into polars)
This nice result is helped by accurately estimating time to the starting line (Alinghi Race 3)
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62J. Craig Mudge ee380 Stanford University 2/19/2003
On each legDisplay
time to next marktime in each tack remainingtime to layline
target boat speedetc
Predict next leg- given assumptions on wind
and mark, use polars to display:-course, wind angles,
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63J. Craig Mudge ee380 Stanford University 2/19/2003
Topics not covered
• Effect of mast on flow past mainsail
• Trim tabs on aft end of keel• Heads-up display in navigator’s sunglasses • Modeling interaction of hull and sails
• Modeling of currents
• Analysis of materials and structure of hulls
• Techniques in rig design and analysis
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64J. Craig Mudge ee380 Stanford University 2/19/2003
BibliographyJoubert, P N. and Oosannen van, P. The Development of the Winged Keel for
Twelve Metre Yachts, Rev. 1986.Killing, Steve.Yacht Design Explained, Norton, New York, 1998.Larsson, L and Eliasson, R. Principles of Yacht Design, 2nd ed. International Marine,
Camden, 2000.Milgram, Jerome H. Fluid Mechanics for Sailing Vessel Design, Annual Review of
Fluid Mechanics, 1998 30:613-653.Marchaj, C A. Sail Performance. International Marine, London, 1996.Sawley, M L. Numerical Flow Simulation for the America’s Cup. EPFL
Newsletter,2002.Whidden, Tom. The art and science of sails, St. Martins Press, New York,1990.
• Email [email protected] for a copy of this bibliography
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65J. Craig Mudge ee380 Stanford University 2/19/2003
High performance yachts in the future
1. Materials– Surfaces
• Low drag (MEMS?)• Vortex generators (a la Formula 1 cars) – also slots, porosity
2. Control of sail shape– Auto-adjust (but without stored energy)
3. Rig and masts4. Better numerical modeling
– Downwind sail design– Sail shape optimization, including design in unsteady
conditions (waves, …)– Coupling of accurate CFD to structural analysis– Hull-sail interaction
Some possibilities
Rules will have to change in some cases.
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66J. Craig Mudge ee380 Stanford University 2/19/2003
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67J. Craig Mudge ee380 Stanford University 2/19/2003
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68J. Craig Mudge ee380 Stanford University 2/19/2003
■ Design shape flying shape
■ Square-rigged
■ Twist onset flow small
■ Extensive experimental data
280 ft
160ft
65ft
Maltese Falcon ideal test case
■ Prototype testing appealing
Stanford Yacht Research
(Gerritsen, Doyle, Perkins)
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69J. Craig Mudge ee380 Stanford University 2/19/2003
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70J. Craig Mudge ee380 Stanford University 2/19/2003
Kiwi clip on or hula
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71J. Craig Mudge ee380 Stanford University 2/19/2003
3DL
Contrast with panelled sails
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72J. Craig Mudge ee380 Stanford University 2/19/2003
Review: computer useArea Type
Design of hull Hydrodynamic modeling (to reduce drag)
Hull appendages Hydrodynamic modeling (lift and drag)
Design of sails Aerodynamic modeling; photogrammatic
Computational Fluid Dynamics (CFD)
Modeling, analysis, and visualization – sails, hulls, appendages
Two boat testing Data collection and data management
Navigation/tactics/ strategy
Performance parameters; predictions for next leg
Campaign Project/financial management, travel, web site
Weather Forecast wind patterns for each race
Sports media Visualization of race course from telemetry