Mercedes-AMG Petronas Lecture - Souppez, 2019...2019/09/10 · Jean-Baptiste R. G. Souppez Mercedes-AMG Petronas Aerodynamic Department Lecture –10th September 2019 41 PARTICLE

Jean-Baptiste R. G. Souppez

Senior Lecturer in Yacht Design and Composite Engineering

[email protected]

Mercedes-AMG Petronas

Aerodynamic Department Lecture

SOLENTU N I V E R S I T Y

ASYMMETRIC SPINNAKERS:DOWNWIND RACING YACHT SAILS RESEARCH AND FINDINGS

1 0 T H S E P T E M B E R 2 0 1 9

https://www.researchgate.net/profile/Jean_Baptiste_Souppez


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ASYMMETRIC SPINNAKERS:DOWNWIND RACING YACHT SAILS RESEARCH AND FINDINGS

1 0 T H S E P T E M B E R 2 0 1 9

JB



https://orcid.org/0000-0003-0217-5819

https://orcid.org/0000-0003-0217-5819



Jean-Baptiste R. G. Souppez Mercedes-AMG Petronas Aerodynamic Department Lecture – 10th September 2019

CONTENTS

3

1. History

2. Upwind vs Downwind Sailing

3. Wind Tunnel Testing of Yacht Sails

4. Aerodynamics of the Circular Arc

5. Leading Edge Vortex

6. Conclusions



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1. HISTORY



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Jean-Baptiste R. G. Souppez Mercedes-AMG Petronas Aerodynamic Department Lecture – 10th September 2019 5

HISTORY

Round the world racing with very close finish?

2012-2013 Vendee Globe: 3 hours 17 min between the first and second after 78 days at see

1866 – Tea Race, Taeping won by 28 minutes after 99 days at sea


HISTORY

Catamaran for the America’s Cup?

2010s

1877 – Herreshoff proposed AC catamaran


HISTORY

Foiling Yachts?

Latest trend

Started in 1898


HISTORY

Canting keel yachts?

1930s



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2. UPWIND VS DOWNWIND SAILING



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UPWIND WIND TRIANGLE

VTVA

βT

βA

True Wind Speed

(TWS)VT

Velocity of the wind relative to a

stationary object.

True Wind Angle

(TWA)βT

Angle between TWS and yacht’s

heading.

Boat Speed VB Velocity of the yacht.

Apparent Wind

Speed (AWS)VA

Velocity wind relative to a moving

object.

Apparent Wind

Angle (AWA)βA

Angle between AWS and yacht’s

heading.VB


UPWIND SAILING EQUILIBRIUM

CL

Boat Track Yaw

VA

βA

Sail Lift

Sail Drag

Aerodynamic ForceSail Side Force

Keel Side ForceHydrodynamic Force

Drive

Drag

𝑭𝑫 = 𝑳𝒔𝒊𝒏𝜷𝑨 −𝑫 𝒄𝒐𝒔 𝜷𝑨

𝑺𝑺𝑭 = 𝑳 𝐜𝐨𝐬𝜷𝑨 +𝑫 𝐬𝐢𝐧 𝜷𝑨


DOWNWIND SAILING

Historically: Vessels sailing downwind

1865: First spinnaker, dedicated downwind sail

1970s: Symmetric spinnakers

1990s: Asymmetric spinnakers (aka Gennaker)


SYMMETRIC SPINNAKER

Drag generating sail

VB

VT

VA

Drag

Lift


ASYMMETRIC SPINNAKER

Lift generating sail

VB

VT

VA

Drag

Lift


ASYMMETRIC SPINNAKER

Lift generating sail



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3. WIND TUNNEL TESTING OF YACHT SAILS



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THE IMPORTANCE OF SAIL FORCES


THE IMPORTANCE OF SAIL FORCES


TWISTED FLOW WIND TUNNEL







Atmospheric boundary layer effect








VELOCITY PREDICTION PROGRAM

The output from the wind tunnel testing then feature in the Velocity Prediction

Program (VPP)

Surge (x): Longitudinal movement of the yacht

Sway (y): Transverse movement of the yacht

Heave (z): Vertical movement of the yacht

Roll (ϕ): Rotation about the longitudinal axis

Pitch (θ): Rotation about the transverse axis

Yaw (β): Rotation about the vertical axis


POLAR PLOT

The polar plot resulting from the VPP presents: True Wind Angle

Boat Speed

Speed achieved with a particular sail…

… in a particular True Wind Speed


POLAR PLOT

It is also used to assess the best Velocity Made Good (VMG)

VB

VTVA

VMG


VELOCITY MADE GOOD

Wind


REAL TIME VPP


WIND TUNNEL TESTING

BUT…



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4. AERODYNAMICS OF THE CIRCULAR ARC



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BACKGROUND

Wind Tunnel assumption: the flow is turbulent (at the scales

typically tested in dedicated wind tunnel facilities)

Inconsistencies noticed in the pressure distribution on wind

tunnel tested models Some exhibit laminar separation bubbles while others do not.

This is characterized by a plateau in the spanwise pressure coefficient


BACKGROUND

Low Reynolds number: discontinuity in the lift and drag (Lombardi, 2014)

Abrupt change in separation point at the same angle (Martin, 2015)


HYPOTHESIS

Hypothesis: these is a combination of critical Reynolds number and critical angle of

attack that will trigger transition.


GEOMETRY

Specifications: Highly cambered: 22.32%

Thin: 1.8mm thick

Chord: 200m

Sharp leading edge

Manufacturing: Carbon prepreg


FORCE MEASUREMENTS

Force measurements undertaken in Solent University’s Hydrodynamic Test Centre: Reynolds numbers: 53k, 68k, 150k and 220k

Angles of Attack: 5 to 20 (5 to 25 at 53k) in 1 degree increments

Angle of attack of 11 degrees for 130k < Re < 160k


FORCE MEASUREMENTS VALIDATION

Validated against Velychko’s (2014) wind tunnel experiment.

Velychko, 2014


FLOW DIAGNOSTICS – PARTICLE IMAGE VELOCIMETRY

Current flume at the University of

Edinburgh


FLOW DIAGNOSTICS – PARTICLE IMAGE VELOCIMETRY


PARTICLE IMAGE VELOCIMETRY – FLOW FIELDS

Delayed separation consistent with the values of Martin (2015) and reduced wake,

characteristic of laminar to turbulent transition.

Sub-Critical

AoA = 14ºSuper-Critical

AoA = 15º


PARTICLE IMAGE VELOCIMETRY – FLOW FIELDS

Delayed separation consistent with the values of Martin (2015) and reduced wake,

characteristic of laminar to turbulent transition


NON-DIMENSIONAL TURBULENT KINETIC ENERGY

𝑢′2 + 𝑣′2 2𝑈∞2






IDEALISED MODEL

Idealised Lift Coefficient:

The flow is turbulent above a critical Reynolds

number of 220k irrelevant of the angle of

attack

Below 220k, there is a combination of

Reynolds number and angle of attack that will

induce transition

What angle of attack is needed to inflate

a soft spinnaker?

And what is the associated Reynolds

number to guarantee a turbulent flow?


IDEAL ANGLE OF ATTACK

11 degrees is the ideal angle of attack

A minimum Re of 144k (±2k) is required


APPLICATIONS

Now allows to explain the inconsistencies noticed: Model & full-scale experiments with a high enough Reynolds number are still valid

Model scale experiments at too low a Reynolds number should be discarded

Interesting case of Bot et al. 2014: LSB at the shallowest AWA

Suggest the critical AoA for that Reynolds

number was not reached yet

Higher AWA however appear to be above the

critical AoA to trigger transition

We can now ensure model scale

experiments appropriately replicate the

full-scale turbulent separation on

spinnakers



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5. LEADING EDGE VORTEX



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BACKGROUND

Leading Edge Vortex (LEV): Coherent vortex formed by a roll up of vorticity at the leading edge

Vorticity convected towards the centre of the vortex

If vorticity if extracted from the axis of the vortex, a stable LEV is achieved

Vorticity is typically extracted inside the vortex core towards the tip of the wing


BACKGROUND

Evidence of LEV on: Delta Wings (1960s)

Insects (1996)

Birds (2004)

Spinnakers (2014) – Numerically

Spinnakers (2017) - Experimentally

“Birds can’t fly”


LEADING EDGE VORTEX


LEV ON SPINNAKERS

Current research question: LEV on thin wings with a sharp leading edge?

How to promote the development and stability of the LEV?

Design characteristic affecting the LEV and its stability?

Performance gain?

Up to +25% Lift


OTHER APPLICATIONS


OTHER APPLICATIONS ?



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6. CONCLUSIONS



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CONCLUSIONS

1. History

2. Upwind vs downwind

3. Wind tunnel testing

4. Aerodynamics of the circular arc

5. Leading edge vortex

Reference: Souppez, J.-B. R. G., Arredondo-Galeana, A. & Viola I. M.,‘Recent Advances in Downwind Sail Aerodynamics’, The 23rd Chesapeake Sailing Yacht Symposium,

Annapolis, Maryland, United States, 2019.

Souppez, Arredondo-Galeana & Viola, 2019.




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THANK YOU



https://orcid.org/0000-0003-0217-5819

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Documents

Mercedes-AMG Petronas Lecture - Souppez, 2019...2019/09/10 · Jean-Baptiste R. G. Souppez Mercedes-AMG Petronas Aerodynamic Department Lecture –10th September 2019 41 PARTICLE