Automobile aerodynamics Gautam Buddha university
Automobile aerodynamics
Gautam Buddha universityBy:-Manish Tomar (10/IME/029)Himant
Sirohi (10/IME/022)Sumit Bhati (10/IME/0contentsAbout Historic
OverviewElements of AerodynamicsAerodynamic toolsEffect of
Aerodynamics on Automobile PerformanceTools of
AerodynamicsValidationAboutAerodynamics is study of the properties
of air, when solid bodies are moving through air. The dynamics
between these two interacting surfaces is aerodynamics.Importance
of Automobile Aerodynamics emerged from Formula races dating back
to 1915.The soul purpose was to reduce drag during initial
development in aerodynamics, and clock faster average times in
formula races.General aspect of aerodynamics was not seen in
passenger vehicles due to low speed till around 1940-50s. As
automobile industry developed, need for aerodynamics was felt, to
increasing stability at high speed and maneuverability.As the speed
limits increased, the development in aerodynamics from F1 started
trickling down to passenger Automobiles.Nowadays there are various
methods available to measure aerodynamics of car.
Historic overviewAutomobile aerodynamics were born from initial
need of drag reduction in formula cars, first foundation was laid
in Indianapolis 500 in 1916, water drop shaped cars came into
existence.The 1924 tropfenwagen was the most significant design of
that era.Then aerodynamics evolved and need for downforce was
realized nad simultaneously tire development took place.Second
figure shows a 1965 chaparral - 2c.
Wings were then widely used in 1966 formula races, it was
introduced with chaparral 2E.Some solutions came in as adjustable
wings and suction fans, to create efficient engines. 1968 Lotus and
chaparral 2J(sucker car) are few examples.Then came modern era cars
with reversed wing underbody and sealing skirts.
Chaparral 2E1968 Lotus
Chaparral 2J
1978 LotusEven the old trucks were usually of non aerodynamics
and box type. When speed limit of trucks were raised, new era of
trucks with hood came in effect.New trucks length shape and size
are governed by many factors, so in trucks COE (Cab over engine) is
widely preferred in India to decrease overall length of
vehicle.
Old Freightliner pickup trucks COE type
New Freightliner Cascadia truckCars are where the aerodynamics
play the major role, so main focus will be on cars.Cars are
generally defined in three types:-HatchbackNotchbackFastbackThese
are defined on the basis of 3 or 2 quarters box design of car.As
fuel is becoming costlier, the automobile companies need to think
on ways of making automobiles efficient and vehicle aerodynamics is
a good area.Elelments of aerodynamicsLift
(Downforce)DragWeightThrustPitch AngleYaw Angle
Pitch angle is an extent to which angle a cars front end will
move during acceleration and deceleration.Yaw angle is defined as
relative angle between direction of motion of vehicle to relative
wind direction.Aerodynamic toolsAirfoilsAirfoil can be defined as a
shape of wing, as seen in cross-section. In orderto describe an
airfoil, we must define the following terms:-The mean camber line
is a line drawn midway between the upper andlower surfaces. The
leading and trailing edge are the most forward an rearward of the
mean camber line.The chord line is a line connecting leading an
trailing edge.The chord length is the distance from the leading to
the trailing edge,measured along the chord line. The camber is the
maximum distance between mean camber line andchord line. The
thickness is the distance between the upper and lower surfaces.
REAR WINGSThese are used to create downforce on vehicle to keep
it stabilized and helps in taking corners at faster speeds.These
produce 30 to 35% of the total downforce on vehicle.
FRONT WINGIt produces approximately 1/3rd of total downforce on
vehicle.It also has a task of efficiently guide the air towards the
body and rear of the car. The turbulent flow impacts the efficiency
of the rear wing.
BARGE BOARDSSIDE SKIRTS to seal the sidepods surfaces and direct
air.VORTEX GENERATORSSTEPPED UNDERBODIESSCOOPSAerodynamics and
performanceThe aerodynamics depends on the body shape and
velocity.The chart on right shows the trend in maximum cornering
acceleration from past 50 years.
Downforce and drag coefficient vs ground clearance for an
inverted airfoil
Lift and drag coefficients for the rear wing of a generic
open-wheel race car. AR = 1.5, and coefficients are based on plan
view area. AR, aspect ratio. [Katz & Dykstra (1989), SAE Paper
89,0600 c 1989 SAE International.]
Lift and drag coefficient variation with front wing flap angle.
Circular symbols represent vehicle total loads and square symbols
represent loads on the front wing only. [Katz & Garcia (2002),
SAE Paper 2002-01-3311 c 2002 SAE International.]
