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 , civilengineering , 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 DIFFERENCEMINIMISE 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 DUCTSIncrease rate of flowTo 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 STUDIOANALYZE CHANGES DURING DESIGNPHASE AND DEVELOPMENTREDUCES TIME TO DEVELOPOPTIMAL DESIGNABLE TO STUDY INDIVIDUALELEMENTS, MORE EFFECTIVE

AERODYNAMIC IMPROVEMENTS IN THE CAR THAT WE ALREADY OWN

Keep your vehicle washed and waxedRemove mud flaps behind wheelsPlace license plate out of air flowAvoid roof-racks or carriersClose 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 aerodynamicefficiency.

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.

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