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
Erasmus LLP Intensive Programme
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
Erasmus LLP Intensive Programme
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
Erasmus LLP Intensive Programme
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
Erasmus LLP Intensive Programme
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