2. Automobile Aerodynamics.
Automobile Aerodynamics includes:
Drag
Lift
• External Flow phenomenon
• Major factors Contributing to flow field around a vehicle
• Use of CFD as simulation tool for the analysis
• Effect of external devices which reduce drag such as
spoilers and air dams.
3. Automotive aerodynamics is the study of
the aerodynamics of road vehicles.
External aerodynamics is the study of flow
around solid objects of various shapes.
4. In vehicle aerodynamics drag is comprised
primarily of two forces:
Frontal pressure
Rear vacuum
o Frontal pressure is caused by the air attempting to
flow around the front of the car
o Rear vacuum is caused by the "hole" left in the air
as the car passes through it.
5. The air molecules travelling along the sides of the car
are at atmospheric pressure, a lower pressure compared to
the molecules at the front of the car.
6. Rear vacuum is caused by the "hole" left in
the air as the car passes through it.
The reason keeping flow attachment is so important is that
the force created by the vacuum far exceeds that created by
frontal pressure, and this can be attributed to the Turbulence
created by the detachment.
7. Every object travelling through air creates either
a lifting or downforce situation. Race cars,SUVs
of course use things like inverted wings to force
the car down onto the track, increasing traction.
The average street car however tends to create
lift. This is because the car body shape itself
generates a low pressure area above itself.
8. The underside of the car is also responsible
for creating lift or downforce. If a car's front
end is lower than the rear end, then the
widening gap between the underside and the
road creates a vacuum, or low pressure area,
and therefore "suction" that equates to
downforce
9. It is a dimensionless quantity that is used to
quantify the resistance of an object in a fluid
environment such as air or water.
is the drag force.
For a certain body shape the drag
coefficient only depends on the Reynolds
number.
10. When the air moving over the vehicle is
separated at the rear end, it leaves a large
low pressure turbulent region behind the
vehicle known as the wake.
This wake contributes to the formation of
pressure drag, which is eventually reduces
the vehicle performance
11. Boundary layer
Separation of flow field
Friction drag
Pressure drag
12. A sport utility vehicle (SUV) is a generic
marketing term for a vehicle similar to a
station wagon, but built on a light-truck
chassis.
SUVs are usually equipped with four-wheel
drive for on- or off-road ability
13. This project is based on the design and
developments of external devices which will
let the manufacturers of Sport Utility Vehicle
(especially known as ‘SUV’) make the present
vehicles more aerodynamically attractive.
The lowering drag coefficient shows the
taste of competitive environment in the field
of designing SUV
14. Lowering the front bumper and bonnet,
inclining the front windshield.
Rounding off the corners and sharp edges.
Extending the front bumper
Make small chamfers at the rear end of the
roof and the side body, there will be a
significant change in the drag.
15. Spoilers: These aerodynamic aids produce
downforce by creating a "dam" at the rear lip
of the trunk. This dam works in a similar
fashion to the windshield, only it creates
higher pressure in the area above the trunk.
16. UseFront Air Dams. Air dams at the front of
the car restrict the flow of air reaching the
underside of the car. This creates a lower
pressure area under the car, effectively
providing downforce.
17. Firstly,
we will produce various designs (4-5)
of windscreen, hood and spoilers.
Then we will perform the various analysis
over the designs by using different values of
Reynolds number in ANSYS.
In ANSYS we will see the pressure distribution
on the body of vehicle induced by fluid
properties to deduce the aerodynamic drag.
