Aerodynamic forces, application of aerodynamics in automotive, Forces act on automotive,

1. APPLICATIONS OF
AERODYNAMICS IN AUTOMOTIVE
Presented By:
Jayesh Deore
Rupesh Fend
Rajatkumar Pawar
Nikhil Nagdev

2. Contents
 Introduction
 Classification
 Applications
 Need of aerodynamics
 Evolution of aerodynamics
 Aerodynamic Forces
 Aerodynamic Devices
 Conclusion

3. Introduction
When objects move through air, forces are generated by the relative motion
between air and surfaces of the body, study of these forces generated by motion of
air is called aerodynamics.
Classification
• On the basis of flow environment
1. External Aerodynamics 2. Internal Aerodynamics
• On the basis of flow behavior
1. Subsonic 2. Sonic 3. Supersonic

4. Field of Application
1. Aerospace engineering
2. Design of automotive
3. Design of ships and sails
4. Design of bridges and buildings

5. Need of Aerodynamics in Automobiles
These are some the major needs of aerodynamics
1. More fuel efficiency
2. Higher speed
3. Good aesthetic and stylish appearance of car
4. More stability of car at higher speed
5. Reduces noise level

6. Evolution of aerodynamics in cars
In 1920’s there were not a factor
like aerodynamics as the cars run
at very low speed, but with
increase of speed it is necessarily
for cars to become more
streamlined , which result in
smooth design.
Up to 1950 the aerodynamic drag
has been cut by 45% of the early
cars. During this time the aesthetic
design of automobile were also
comes in to the competition.
During 1970’s there were a fuel crisis and
so the demand for more economical cars
became greater, which lead to changes in
car aerodynamics for achieving more
economical cars.

7. Evolution of aerodynamic in cars continued……….Till present
Now today we have the best
aerodynamic automotive, which
are best in aesthetic as well as in
fuel efficiency. Now all the
automotive vehicles are
manufactured aerodynamically.
But this evolution will never
stop.

8. Aerodynamic forces on aerofoil
Consider a aerofoil move through air,
forces which are considered for
aerodynamic analysis over aerofoil are,
1. Lift
2. Drag
3. Weight
4. Thrust.

9. Aerodynamic forces continued………
1.Lift: It is the sum of all dynamic forces on a body normal to the
direction of external flow around the body. It results to rise by
creating pressure difference.
2.Drag: It is the sum of all external forces in the direction of fluid
flow, so it acts to the direction of the object. Due to this it opposes
forward motion of the body.
3.Weight: It is just the weight of the object that we all know. i.e.
mass multiplied by gravitational acceleration (m*a).
4.Thrust: It is the force produced by the body by some kind of
mechanism in the opposite direction of drag, so that it can move
through fluid (air).

10. Aerodynamic forces continued………
Aerodynamic
Forces
Drag Force Lift Force
Pressure Drag
(due to pressure stresses)
Friction Drag
(due to shear stresses)
Up Force
(positive lift)
Down Force
(negative lift)

11. Aerodynamic forces continued………
Drag Force
Drag force is combination of Friction drag which occurred due to
shear stress and pressure drag which occurred due air separation or
simply called pressure difference.
Friction Drag
As the name suggests this force is due to friction and viscosity of air
The friction drag occurs when the air comes in contact with the surface
of vehicle, that means the more the air comes in contact with air the
more friction drag will developed.
“The more streamlined body have more friction drag.”
Friction drag is calculated as:
𝜏dASinθ

12. In the 1st figure which is a car, the surface area
of car in contact with air is large so the friction
drag will more.
While in 2nd figure, there is a bus whose surface
area in contact with air is less, which leads to the
lower friction drag.
Aerodynamic forces continued………

13. Aerodynamic forces continued………
Pressure drag
Now, the pressure drag is due to the
pressure differences which occur due to
separation of air.
In friction drag we studied that the more
streamline body the more friction drag, but
the pressure drag is exactly opposite of that.
The body of automotive is made more
streamline to avoid separation of air which
leads to less pressure drag.
The pressure drag is calculated as:
𝑃dACosθ

14. Aerodynamic forces continued………
Total Drag
Total drag is the submission of friction drag and pressure drag and it is
calculated as
(𝜏dASinθ + PdACosθ)

15. Aerodynamic forces continued………
To obtain minimum drag force the
streamline shape of body of car must be
balanced .
The graph show the relation of different
drag force with respect to streamlined
shape.

16. Aerodynamic forces continued………
Coefficient of drag
Coefficient of drag is constant of drag
which contains all the complex
dependencies and is usually determined
experimentally. Coefficient of drag
depend upon the density, frontal area and
the velocity.
The mathematical formula for
coefficient of drag is:

17. Aerodynamic forces continued………
Lift force
It is the sum of all dynamic forces on a body normal to the direction of external
flow around the body. In simple it is perpendicular force to the body. The lift
force may be positive called as up force or simply lift and the negative lift
called as down force. The lift also occurs due to the pressure difference.
Lift (Positive lift)
Positive lift occurs when there is high pressure above the
aerofoil and low pressure below the aerofoil, and due
this pressure difference the upward force exerted over
the body. The positive lift aerofoil is generally used in
the aircrafts to obtain upward lift.

18. Aerodynamic forces continued………
Down force (Negative lift)
The down force is the same as the lift, the difference
is only that it act in the downward direction. The
Down force (negative lift) occurs when there is high
pressure above the section of the body and low
pressure below the section of the body, which creates
pressure difference and develops a force in
downward direction.
The down force is calculated as:
Down force is an important parameter. While
considering performance it necessary that a proper
amount of down force is created by minimizing the
drag force, to obtain maximum fuel efficiency. Due
to down force proper gripping of wheel and ground
is possible .

19. Aerodynamic forces continued………
Coefficient of Lift
It is also a constant dimension less
number which is determined
experimentally. It depends upon
the density, surface area and the
velocity of the vehicle.
The mathematical formula for
coefficient of lift is:

20. Aerodynamic Devices
1.Spoiler: Spoilers on cars are used to prevent lift by
placing an obstruction in the path of lift-creating airflow.
This causes the path of the air to change, so that the airflow
at the rear of the vehicle leaves in a horizontal or upward
manner, thus not producing lift.
2.Wings: The wings used in racing cars are similar to that
of the wings in airplane the only difference in its cross
section. The cross section of wings in cars is opposite to
that of the wings in airplane. The function of wings is
produce the down force. However, the benefit of down
force comes at the expense of additional drag.

21. Aerodynamic Devices continued………
3.Diffusers: Diffuser is a portion of car which is
underneath of car. Diffuser increases the velocity of air
flowing below the car. Thus reducing its pressure due to
which a down force is created. There is one more
function of diffuser it reduces the flow separation which
leads to reduce in drag force.
4.Naca Duct: The function of naca duct is to increase the flow rate
of air without affecting the drag force. The naca duct suck the air inside it
and this air is used for the cooling purpose. It is especially favored in
racing car design.

22. Conclusion
In the conclusion we could only say that the aerodynamics is very large,
Interesting and important part of engineering. By using aerodynamics
millions of rupees are saved in the form of fuel consumption. We have
only explained the one application of it, but this is not limited to this it
has infinite number of applications from the Golf balls to fins of the
Rocket.

23. Thank You
Thank You