Date post: | 20-Dec-2014 |
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Automotive |
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AERODYNAMICS IN CARS
ByRavi malla thakuriU11ME380 3nd YearB.Tech (Mech)
INTRODUCTION
AERODYNAMICS :
Study of forces generated by motion of air on moving body.
CLASSIFACATION OF AERODYNAMICS :
external and internal, subsonic , supersonic , hypersonic
FIELDS OF APPLICATION :
aerospace engineering, design of automobiles , ships , civil
engineering , design of bridges etc.
AERODYNAMIC FORCES ON A BODY
LIFT(DOWNFORCE)
DRAG
WEIGHT
THRUST
HISTORY OF EVOLUTION OFAERODYNAMICS IN CARS
DESIGN¶S IN EARLY 20th CENTURY :cars with low speeds, no aerodynamic problems.
CAR¶S IN THE EARLY 50s :cars designed for big familys , complete negligenceof aerodynamics.
CARS AFTER 70s :fuel crisis , need of economic designs , evolution ofaerodynamics.
WHY WE NEED TO IMPROVE AERODYNAMICS IN CARS
SPEED
better aerodynamics higher will be the speeds.
FUEL EFFICIENCY
better aerodynamics , less work for engine.
FRONT END
FRONTAL PRESSUREPRESSURE DIFFERENCE
MINIMISE FRONTAL AREAREDUCE cd
REAR END
REAR VACCUM
FLOW DETACHEMENT
TURBULANCE
AERODYNAMICS IN MCLARENF1
SPECIFICATIONS
FRONT END
REAR END
SCOOPS
WINGS Mclaren F1
AERODYNAMIC DEVICES
SPOILERS
NACA DUCTS
Increase rate of flow
To expose air to areas not exposed todirect air flow.
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METHODS TO EVALUATE AERODYNAMICS IN CARS
WIND TUNNELSResearch tool to study effect of airmoving over a solid object.Trial and error process.Special pressure paints for analysis.Detailed analysis of air flow patterns.
Analyzing for the optimal design.
SOFTWARES
DEVELOPMENTS IN CAD
ANSYS, CATIA,ALIAS STUDIO
ANALYZE CHANGES DURING DESIGNPHASE AND DEVELOPMENT
REDUCES TIME TO DEVELOPOPTIMAL DESIGN
ABLE TO STUDY INDIVIDUALELEMENTS, MORE EFFECTIVE
AERODYNAMIC IMPROVEMENTS IN THE CAR THAT WE ALREADY OWN
Keep your vehicle washed and waxed
Remove mud flaps behind wheels
Place license plate out of air flow
Avoid roof-racks or carriers
Close windows, close sunroof
SCOOPS
ENGINE COOLING
INCREASES FLOW RATE OF AIR
WINGS
PRODUCE DOWNFORCE
REDUCE DRAG
COEFFICIENT OF DRAG
Drag = 1/2xd x Cd x A Xv2
Measure of aerodynamic
efficiency.
Drag Reduction System
The Drag Reduction System (DRS) isperhaps the most interesting of thenew Technical Regulations imposed onFormula 1 in 2011. Its purpose? Topromote overtaking by counteractingthe loss of downforce incurred whenfollowing another Formula 1 car. This isacheived by reducing the followingcar's aerodynamic drag by opening adriver activated flap on the rear wing ofthe car. The device opens anadjustable flap on the rear wing of thecar (which when closed creates moredownforce for greater cornering) toreduce downforce, thus giving apursuing car more speed and a greaterchance of overtaking a car in front.
Functional description
The horizontal elements of the rear wingconsist of the main plane and the flap. TheDRS allows the flap to lift a maximum of 50mm from the fixed main plane. This reducesopposition (drag) to airflow against the wingand results in less downforce. In the absenceof significant lateral forces (straight line), lessdownforce allows faster acceleration andpotential top speed, unless limited by thetop gear ratio and engine rev limiter.
Diffuser
A diffuser, in an automotive context, is a shaped section ofthe car underbody which improves thecar's aerodynamic properties by enhancing the transitionbetween the high-velocity airflow underneath the car and themuch slower freestream airflow of the ambient atmosphere. Itworks by providing a space for the underbody airflow todecelerate and expand (in area, density remains constant at thespeeds that cars travel) so that it does not cause excessive flowseparation and drag, by providing a degree of "wake infill". Thediffuser itself accelerates the flow in front of it, which helpsgenerate downforce.
Operation
When a diffuser is used, the air flows into theunderbody from the front and sides of thecar, accelerates and reduces pressure. There is asuction peak at the transition of the flat bottomand diffuser. The diffuser then eases this highvelocity air back to normal velocity and also helpsfill in the area behind the car making the wholeunderbody a more efficient downforce producingdevice by reducing drag on the car and increasingdownforce. The diffuser also imparts upwardmomentum to the air which further increasesdownforce.
THANK YOU