Aerodynamics of automobiles

Aerodynamics of automobilesPresentation of Netta Laczkovics

Budapest University of Technology and EconomicsFaculty of Mechanical Engineering Bsc

Major in Industrial Product Design Engineering

English for Transportation Engineers 2015

Contents

Introduction- The purpose of aerodynamic analysis Fundamentals of aerodynamics. Basic equations Aerodynamics of automobiles History of car body desing Top drag coefficients of today Conclusion

Sources

IntroductionThe purpose of aerodynamic analysis is to optimize

consumption

acceleration

maximum speed

emission

comfort

noise level

stability (controllability, directional control, side-wind

sensitivity)

contamination of the body

cooling of the brakes and the engine

Fundamentals of aerodynamics

If the streamlines are curved pressure increases perpendicular to them, outwards from the centre of curvature

2p v

n R

n: co-ordinate normal to streamlineR: radius of streamline curvature where

Fundamentals of aerodynamics

DD

FC

v A2

Acting forces

DC : Drag coefficient

Drag force [N]

Density [kg/m3]

Velocity [m/s]

Cross section area [m2]

DF :

:v :A :

Basic equations

Acting forces

2 'p f

A A

F v C dA C e dA2

p2

ppC

v2

' 0f

2C

v2

'p fF f , v,A,C ,C p

'f

3 C 1

C 0,01

DP F v 2D DF v C A

2

Pressure coefficientpC : Skin friction coefficient'fC :

Power and maximum speed

Boundary layer separation and separation bubbles

Aerodynamics of automobiles

Boundary layer separation, separation bubbles and vortexes

Aerodynamics of automobiles

Aerodynamics of automobiles

Boundary layer separation, separation bubbles and vortexes

Aerodynamics of automobiles

Reduction of aerodynamic drag

Front

Windshield and A-pillars

Roof

Rear

Side Panels

Aerodynamics of automobiles

Reduction of aerodynamic drag

Underbody

Attachment –front spoiler

- rear wing spoiler

Wheels 50% of theDC

History of car body designI. Period: Adaptation of shapes from other fields 1900-1920

1914 – Zeppelin – Alfa Romeo

1913 – Boat – Audi Alpensieger

1899 – Torpedo

History of car body designII. Period: Streamlining 1920-1970 - Adapting the resaults of airplane and airship development

1937 – Tatraplan 1933-Audi 2L andDaimler- Benz 200

Cars based on Pál Járay’s ideas

History of car body designIII. Period: Detail optimization 1970-1990 - Tiny changes that make significant resaults

History of car body designIV. Period: Shape optimization 1990- today

Designing car body close to the ideal shape, then trying to turn into real vehicle with the least changes possible

Lexus LFA Coupe

Alfa Romeo Brera

History of car body designLowering the drag coefficient

History of car body design

The first shape-optimized car

Audi 100 with Cd 0.3 (1982- 1991)

Top drag coefficients of today’s cars

Today’s most aerodynamic cars in production

Mercedes –Benz CLA with Cd 0.22

(2013- present)

Today’s most aerodynamic cars in production

Volkswagen XL1 with Cd 0.19

(2013- present)

Conclusion Drag coefficient depends on many different factors There are basic principles to reduce aerodynamic drag There is no one and only solution for optimization Does not exsist one optimum car body shape Can reach significant solutions with small changes Interference occours by modifying

In optimisation besides wind tunnel investigations numerical simulation of flow field (CFD) has become more and more important

Sourceshttp://www.ara.bme.hu/http://www.car-engineer.com/mercedes-cla-is-the-most-aerodynamic-production-car-of-the-world/http://motorburn.com/2014/01/12-of-the-most-aerodynamic-cars-in-production-right-now/http://www.car-revs-daily.com/2014/10/28/2007-lexus-lf-a-roadster/http://forums.vwvortex.com/showthread.php?7005928-Lost-in-Translation-Viable-concept-cars-that-failed-to-deliver&p=85925579&viewfull=1http://en.wikipedia.org/wiki/Automobile_drag_coefficienthttp://www.gencoupe.com/general-discussion/224609-2015-gen-coupe-rumored-released-later-year.htmlhttps://gr8autotech.wordpress.com/2013/06/16/vehicular-aerodynamics/http://www.kasravi.com/cmu/tec452/aerodynamics/vehicleaero.htm

Thank you for your attention!

Any question?