Erasmus LLP Intensive Programme

Aerodynamics of theHPV

From Fluid Mechanics to a Practical Design

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 1

Jochem De Vriendt, Karel de Grote-Hogeschool,Belgium

Erasmus LLP Intensive Programme

Introduction

The Need of an Aerodynamic Body Shape Equation of Motion Aerodynamic Drag Properties of Air Basic Equations

Drag Fractions and their Local Origins

Conclusions

Contents

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 2

Erasmus LLP Intensive Programme

Fluid Mechanics

Introduction

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK 2012Project code: 2011-1-GR1-ERA10-06828 3

Erasmus LLP Intensive Programme

The Need of an Aerodynamical Shape

Equation of Motion

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 4

sinmgdt

dvmRDFt

ClimbingResistance

AccelerationResistance

RollingResistance

AerodynamicDrag

TractiveForce

Erasmus LLP Intensive Programme

The Need of an Aerodynamical Shape

Aerodynamic Drag

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 5

ACvD D²2

Erasmus LLP Intensive Programme

The Need of an Aerodynamical Shape

Properties of Air

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 6

sm²104607.1 5

²107894.1 5 mNs

4²²

2250.1 mNsm

kg

Erasmus LLP Intensive Programme

The Need of an Aerodynamical Shape

Basic Equations

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 7

•Inviscid Incompressible Flow: Bernoulli’s Equation

•Effects of Viscosity: Laminar and TurbulentBoundary Layer Development

Erasmus LLP Intensive Programme

The Need of an Aerodynamical Shape

Basic EquationsInviscid Flow

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 8

Bernoulli’s Equation:

.²2

ConstvPPt

DynamicPressure

Staticpressure

TotalPressure

Erasmus LLP Intensive Programme

The Need of an Aerodynamical Shape

Basic EquationsEffects of a Viscous Flow

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 9

Laminar & Turbulent Boundary Layer Development:Reynolds number

External Internal

410.Re

lV

l

dVm.Re

ForcesViscous

ForcesInertial

Erasmus LLP Intensive Programme

The Need of an Aerodynamical Shape

Basic EquationsEffects of a Viscous Flow

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 10

Separation

Flow Separation of the Boundary Layer in Point A andReverse Flow

Erasmus LLP Intensive Programme

The Need of an Aerodynamical Shape

Basic EquationsEffects of a Viscous Flow

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 11

Friction Drag

Determination of the Drag of a Body(two-dimensional flow)

Erasmus LLP Intensive Programme

The Need of an Aerodynamical Shape

Basic EquationsEffects of a Viscous Flow

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 12

Pressure Drag

Erasmus LLP Intensive Programme

The Need of an Aerodynamical Shape

Basic EquationsEffects of a Viscous Flow

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 13

Overall Forces and Moments

Lift, Drag, Side Force, Pitching Moment, Rolling Moment,Yawing Moment

Erasmus LLP Intensive Programme

The Need of an Aerodynamical Shape

Basic EquationsEffects of a Viscous Flow

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 14

Overall Forces and Moments

Lift & Pitching Moment

Erasmus LLP Intensive Programme

The Need of an Aerodynamical Shape

Basic EquationsEffects of a Viscous Flow

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 15

Overall Forces and Moments

Front Lift & Drag Rear Lift & Drag

Erasmus LLP Intensive Programme

The Need of an Aerodynamical Shape

Basic EquationsEffects of a Viscous Flow

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 16

Aerodynamic Noise

•Periodic Flow Separation•Downstream Regular Pattern of Vortices

=von Kármán Vortex Street

Erasmus LLP Intensive Programme

The Need of an Aerodynamical Shape

Basic EquationsEffects of a Viscous Flow

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 17

Transport of Solids

Particle Motion in a Flow Field attacking a Windshield:a) velocity vectorsb) acting forces

Erasmus LLP Intensive Programme

Drag Fractions and their Local Origins

Flow Field around a car

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 18

•Tangential force T(β) underside wind•Main airflow separations arounda car (front & back)

Erasmus LLP Intensive Programme

Drag Fractions and their Local Origins

Flow Field around a car

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 19

Airflow patterns on a fastback withdifferent slant anglesφ

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Drag Fractions and their Local Origins

Front End

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 20

Influence of front end body contouron drag

Erasmus LLP Intensive Programme

Drag Fractions and their Local Origins

Windshield & ~wipers

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 21

Reduction of Drag with hoodinclination angleα andwindshield inclination angleδ

Flow separation point S andreattachment point R as a functionof the windshield inclination angleγ

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Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 22

Effect of roof camber onCd and absolute drag

Flow regime around thepassenger compartment of aconvertible, top down

Drag Fractions and their Local Origins

Roof & Convertibles

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Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 23

Drag Fractions and their Local Origins

Rear End – Boat-Tailing

Drag reduction by Boat-tailing on Record Vehicles

Erasmus LLP Intensive Programme

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 24

Boat-tailing on a Fastback:1. φ = 25°2. φ = 25), underbody raised

byα = 10°3. Idem with side boat-tailing

ofδ = 10°4. Idem with chamfered top

edge

Drag Fractions and their Local Origins

Rear End – Fastback

Influence of slant angleφ and rear length lo ondrag

Erasmus LLP Intensive Programme

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 25

Drag Fractions and their Local Origins

Rear End – Fastback

Effect of rear-end height z ondrag coefficient CD for a carwith rounded rear

Erasmus LLP Intensive Programme

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 26

Drag Fractions and their Local Origins

Plan View & Side Panels

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Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 27

Drag Fractions and their Local Origins

Underbody & Ground Clearance

Air flow under a car ina nozzle-type spaceresults in lowpressure andnegative lift = drag

Erasmus LLP Intensive Programme

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 28

Drag Fractions and their Local Origins

Wheels & Wheel Housings, reducingSplash & Spray

Increase in the dragand lift of a low-dragvehicle body by addingthe wheels

Flow pattern of a wheel rollingon the ground

Erasmus LLP Intensive Programme

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 29

Drag Fractions and their Local Origins

Wheels & Wheel Housings, reducingSplash & Spray

Drag and lift on an isolatedwheel with and withoutrotation

Effect of wheelhousing VH on thedrag and lift of anenclosed wheel

Erasmus LLP Intensive Programme

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 30

Drag Fractions and their Local Origins

Outside Mirrors

•Attachments (mirrors &antennas) create drag•Small frontal area•(wind noise & dirt deposition)

Erasmus LLP Intensive Programme

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 31

Drag Fractions and their Local Origins

Shape Optimization

Starting from a Basic Body,the development processprogressively transformsinto a car

Comparison of differentfundamental bodies

Erasmus LLP Intensive Programme

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 32

Drag Fractions and their Local Origins

Importance of Surface Quality, Water& Dirt Accumulation

Effect of surface roughness onlaminar;

a)No effectb)Transition due to roughness

and turbulent boundary layers;

c)Hydraulically smoothd)Increased drag due toroughness

Critical Roughness:

Permissible Roughness:

4 Re

4.2

x

critk

xx

kperm

Re

100

Erasmus LLP Intensive Programme

Conclusions

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 33

1. Formulate yourconcept

2. Design3. Calculate4. Redesign5. Recalculate6. Re-redesign7. Re-recalculate

8. Consider yourthoughts

9. Start all overagain

10.And again…

Erasmus LLP Intensive Programme

Thanks for your attention

Powering the Future With Zero Emission and Human Powered Vehicles – Bradford, UK, 2012Project code: 2011-1-GR1-ERA10-06828 34

•Fundamentals of Sailplane Design,Fred Thomas, ISBN 0-9669553-0-7

• Design, Leistung und Dynamik von Segelflugmodellen,Helmut Quabecq, HQ Modellflugliteratur, Finkenweg 39,D-64832 Babenhausen

•Aerodynamics of Road Vehicles,Wolf-Heinrich Hucho, ISBN 0-7680-0029-7