Report on Conceptual Frontal Design of a Vehicle. Better aerodynamic frontal designing procedure of vehicle.

1. Internship Report
On
Conceptual Aerodynamic
Frontal Design of a Vehicle
(May-June 2013)
AMITY SCHOOL OF ENGINEERING & TECHNOLOGY
Submitted by: Submitted to:
Akshay Mistri Mr. Sonu Sharma
Abhishek Thakur (Faculty Guide)
Sarthak Anand
Tushar Rastogi
Prog. /Section: B.Tech 5MAE3 (2011-15)

2. ACKNOWLEDGEMENT
The special thanks goes to Mr.Sonu Sharma. The supervision and support that he gave truly
helped the progression and smoothness of the internship program. The co-operation
is highly appreciated.
Topics studied during the project were highly educative and interesting. This internship
program has made us realize the value of working together as a team and gave us a new
experience of working in aerodynamics field.
This training program gave us opportunity to work in different fields and exposed us to topics
of great interest.
We are also thankful to all the aerodynamics faculties who supported us to complete this project
successfully.
Last but not the least, we would also like to thank lab assistant faculties for their kind support.
It would have been very difficult for us to complete the experiment on our models without their
assistance.

3. ABSTRACT
The objective of this project is to modify the frontal design of existing vehicles
aerodynamically. Every vehicle in motion has some air drag associated with it. Hence it is
required to streamline the shape of the vehicles to produce minimum air drag which in return
can increase the efficiency of vehicles.
The above objective of modifying the shape of vehicles for a better aerodynamic shape was
accomplished by making few models with different front shape which can be practically
manufactured with least amount of changes in the present situation. All the models were tested
for drag force under similar conditions for comparison.
After the test a model with least drag force is chosen as the final model which is the final result
of our prime objective.
The final model so obtained is far better aerodynamic than present shapes of currently running
transportation buses and trucks. Also the model obtained is technically feasible to manufacture
with current technology.
Thus the better aerodynamic shape will ensure less amount of drag force and will increase the
efficiency of existing vehicles.

4. Contents
Title Page
1.Introduction 01
2.Material 02-05
2.1 Adjusting vehicle shape to reduce
drag
03
3.Methodology 05-07
3.1. Drag force equation 06
3.2 Dimensions 07
3.3 Force on a real bus 07
4.Results 07-12
4.1 Drag force table 08
4.2 Newton’s Sine Square law 09
4.3 Coefficient of Drag 10
4.4 Drag force on actual bus 11
4.5 Increase in fuel efficiency 11-12
5.Conclusion 12
6.References 13

5. 1. Introduction
Aerodynamics deals with all the processes that can be observed in flows around or through a
body. The drag co-efficient Cw is determined in a wind tunnel. The lower the Cw value the
higher the final speed results in lower fuel consumption. In the light of increasing fuel prices,
it has become important for all commercial vehicle manufacturers to have favorable
aerodynamic design to improve the Cw value. The recent trend is to have fully paneled
commercial vehicles. Aerodynamics is used in many fields. It is also used in road cars and
mainly it is applied in designing an Aeroplane. The frictional force of aerodynamic drag
increases significantly with vehicle speed. This concept of increasing and decreasing drag force
has a great effect on the speed of vehicle. The front design of the vehicle is always taken into
consideration, it is mainly the frontal design of the racing cars which makes it run faster as the
air is not restricted but it is allowed to flow smoothly. As in Automobile shape plays an
important role in reducing drag at higher speed. The frontal design model of the vehicle is made
at different angles and it is tested in the wind tunnel so as to get the reduced drag. The shape
of a car, as the aerodynamic suggests, is largely responsible for how much drag the car has.
Ideally, the car body should have a small grill, to minimize frontal pressure, minimal ground
clearance below the grill, to minimize air flow under the car. It should also have a converging
"Tail" to keep the air flow attached. Apart from Rolling resistance, the Aerodynamic Drag also
represent the largest proportion of the overall resistance. It increases in the same way as that
of rolling resistance on movement of the vehicle and arises with increase in driving speed.

6. 2. Materials
This project “conceptual Aerodynamics of frontal design of the vehicle” is mainly
associated in finding the drag force when the vehicle moves with great speed. To find the
drag force four models were made, inclined at different angles so as to reduce the drag
force, 60 degree, 90 degree, 120degree, 180 degree where tested on the wind tunnel with
the help of the apparatus “3 component balance”. The models were made of hard cardboard,
it was assembled strongly so that it can resist the force of the air in the wind tunnel. The
cardboard made was varnished and was made smooth and it was painted so as to avoid
errors while finding the drag.
Fig.1 A Test Model [90 deg.] mounted in Wind Tunnel
In order to optimise the vehicle design with regard to aerodynamic the front section of the
driver’s cabin is rounded off in conjunction with the air deflection elements and the use of
front apron. An aerodynamically designed drivers cabin alone, however leads to reinforced
air flow to the non optimised superstructure. The total Cw value then reached is even higher
than that of the commercial vehicles with a squared drivers cab and non optimised

7. superstructure. The reason for this is that with squared drivers cab the front section of the
superstructure is located in a separation zone and hence exposed to lower aerodynamic
drag. Fully panelled commercial vehicles achieve best consumption values and hence
increase the benefit to the fleet operators. In order to significantly reduce the aerodynamic
drag of the commercial vehicle with superstructure, a roof spoiler on the drivers cab with
side flaps and roof attachment is incorporated
2.1 Adjusting vehicle shape to reduce drag
The process of reducing the drag coefficient of a vehicle by altering the vehicle shape is
called streamlining. It was determined during the middle of the 20th century that the most
streamlined shape is a teardrop
Fig.2 Teardrop-shaped profiles are very aerodynamic and yield little drag
Although this design was emulated in various streamlined concept car models, the shape was
found to be impractical when designing an actual car, mainly due to the long and narrow end.
In case of buses teardrop shape is not given due to its large and heavy size. However, the air
that flows around the car swirls around the rear much more for the actual vehicle profile as
compared with the teardrop profile. These swirls are called vortices, and they represent a low-
pressure area behind the car. The low pressure behind the car creates a suction effect that tries

8. to pull the vehicle backwards. Therefore, reducing the size of the separation zone, which is the
area behind the car containing the vortices behind the car, is one of the predominant methods
of decreasing aerodynamic drag. This can be done by slightly tapering the rear end of a car to
reduce the size of the separation zone. As counterintuitive as it may seem, the rear section of
the car is the cause of the most drag on a vehicle. This is the same reason why the example of
holding a traffic cone outside of a car window has less drag when pointed away from the
direction a vehicle is moving.
There is a difference in the aerodynamics on the bus and truck. However the physics are
essentially the same. However, the aerodynamics of the bus is considerably better than those
of the truck. There are two reasons for this. On the one hand, the bus is an enclosed body and
its aerodynamic development is the responsibility of the manufacturer. On the other hand, the
focus with transportation of persons is not so much on maximum interior volume, rather on
maximum comfort. We can therefore optimise the bus aerodynamically from the front to the
rear. With the truck on the other hand, there is a towing vehicle and a separate semitrailer or
body designed by an independent body manufacturer who places utmost importance on
maximum load capacity within legal limits. We, as a towing vehicle manufacturer, also devote
attention to the needs of the driver and attempt to design the cab to be as spacious as possible.
This causes it be relatively square, which is not aerodynamically optimal. With the bus we have
more design freedom and can realise aerodynamic shapes easier, that means design the front to
be rounder. Taperings at the rear are also possible. The smaller the Cw (drag coefficient) value,
the more streamlined is the vehicle. Through good aerodynamics we can save up to 2.0 litres
fuel per 100 kilometres for coaches, depending on how good the initial state is. The following
graph depicts the amount of fuel used for upcoming different types of forces.

9. Fig.3 Fuel Consumption in Various Situations
3.Methodology
We constructed four scaled down models of a standard size urban bus whose specifications
were taken from Urban Bus specifications- II, Ministry of Urban Development, Government
of India. The only difference in the scaled down models were the front faces as can be seen
from the pictures below.
Fig.4 Models with 60, 90, 120, 180 degree face respectively
It must be noted that the overall length, width, height and as a result the frontal area of all the
models is kept same. This kind of similarities makes the models comparable.

10. All the models were tested for aerodynamic drag force in wind tunnel with identical fluid (air)
velocity of about 26 m/sec [93.6 km/hr]. The mounting in the wind tunnel had an electronic
setup to which a “3 Component Balance” was connected.
This 3 Component Balance gives us values of lift, drag and pitching moment in Kg-f in two
modes i.e. Wind off and Wind on modes. Actual values of drag, lift and pitching moment can
be obtained by subtracting Wind off mode values from Wind on mode values. But as our prime
concern was drag force, we kept a check only on that.
The Drag force coefficient can be found out from the equation,
𝑭 =
𝟏
𝟐
𝑫𝑽 𝟐
𝑪 𝑫 𝑨 .… Eq-1 [1]
where F is Drag Force
D is Fluid Density
V is Fluid Velocity
CD is Drag Coefficient
A is Frontal Area
3.1 Dimensions
Standard bus specifications: - Scaled down model specifications: -
Overall Length 12 metre
Overall Width 2.6 metre
Overall Height 3.8 metre
Scaling ratio for scaled down model: - [28:1]
3.2 Force on a real bus
Since the dimensions of model are scaled down by a factor of 28, area will be scaled by a factor
of (28)2. …. {Since area= (dimension) 2}
Overall Length 20 cm
Overall Width 9.3 cm
Overall Height 13.5 cm

11. From equation 𝐹 =
1
2
𝐷𝑉2
𝐶 𝐷 𝐴 ,
we can say that F (drag) is directly proportional to A (frontal area)
So, Drag force on a real bus FR will also scaled up by a factor of (28)2.
Therefore,
FR = (28)2 F ….Eq-2
4.Results
Several values of drag force were taken to reduce error and hence to obtain a more precise
result. These values are obtained by considering 5 second intervals and noting them from the
display of 3 component balance. With several values an average drag force can be found.
Multiplying the drag force by acceleration due to gravity “g” gives the drag force in Newton
which is the S.I unit of force.
The values of drag force are as follows -:
4.1 Table-1
S.No Model
(According to
degree of face)
Drag Force
(Kg-f)
(5 sec interval
of run)
Drag Force
(Average)
(Kg-f)
Drag Force
(Newton)
1 60 0.268 0.384 3.767
0.419
0.424
0.426
2 90 0.504 0.498 4.885
0.493
0.502
0.495
3 120 0.608 0.616 6.042
0.620

12. 0.625
0.614
4 180 0.750 0.757 7.426
0.760
0.755
0.765
It’s essential to take several values of drag force to obtain an accurate value. Several values
which were taken with interval of 5 seconds are depicted below in a graph. The bottom most
profile is of model with 60 deg. face angle. Red profile represents model with 90 deg. face
angle then green profile represents model with 120 deg. face angle with a purple profile
representing model with 180 deg. face angle on top.
Graph 1
Drag Force (Kg-f) v/s Time of run
4.2 Newton’s Sine Square Law
It can be seen from table-1 that drag force increases as angle at the face increases. This can also
said theoretically using Newton’s Sine Square law which states that hydrodynamic force on
0.268
0.419 0.424 0.426
0.504 0.493 0.502 0.495
0.608 0.62 0.625 0.614
0.75 0.76 0.755 0.765
0.2
0.3
0.4
0.5
0.6
0.7
0.8
5 10 15 20
60 Degree
90 Degree
120 Degree
180 Degree
Drag
Force
(Kg-f)
Time of run (seconds)

13. surface is directly proportional to angle Q, where angle Q (theta) is shown in the picture given
below.
Fig.5
Rectilinear stream of discrete particles in our case is flow of air and body shown is the front
face of the bus. Comparison of drag force for the four models is shown below.
Graph 2
Fig.6 Drag Force (Kg-f) v/s Models
0.384
0.498
0.616
0.757
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
60 Degree 90 Degree 120 Degree 180 Degree
Drag Force for different Models
Drag
Force
(Kg-f)
DifferentModels

14. 4.3 Coefficient of Drag
Drag coefficient can be found using the equation,
F= 0.5[D][V2][CD][A]
Where F (drag force) = 3.769 N (60 deg.) D (fluid density) =1.225Kg/m3
= 4.89 N (90 deg.) V (fluid velocity) = 26 m/sec
= 6.05 N (120 deg.)
= 7.431 N (180 deg.)
A (frontal area) = 0.135 X 0.0928 m2
= 0.012528 m2
Substituting the values mentioned above in the equation, drag coefficient can be found easily.
Model (According to Face angle) Drag Coefficient
60 deg. 0.72
90 deg. 0.94
120 deg. 1.17
180 deg. 1.43
4.4 Drag force on an actual bus
Drag force on a real bus can be calculated using equation,
FR = (28)2 (F) where FR is real drag force
F is model drag force
Model (according to face angle) Force (Newton)
60 deg. 2954.89
90 deg. 3833.76
120 deg. 4743.20
180 deg. 5825.90

15. 4.5 Increase in fuel efficiency
We know that least amount of drag is experienced is model with 60 deg. face angle. So, we
will compare that model with 180 deg face model which represents the current condition of
buses and trucks.
Increase in fuel efficiency is derived by comparing the energy contents of drag force and the
fuel used to overcome that drag force. Generally the fuel used in buses and trucks is diesel, so
we will assume our fuel as diesel only and speed 26 m/sec.
4.5.1 Reduction in drag force when 60 deg face model is used in place of 180 deg
face model = 5825.90 – 2954.89 N
= 2871.01 N
4.5.2 Amount of energy associated with this reduction in drag force
= (Reduction in drag force) X (Distance moved by bus per second)
= (2871.01 N) X (26 m/sec)
= 74646.26 Joules
4.5.3 Latent heat of diesel[2] = 34.92 Mega Joule/ litre
4.5.4 Amount of diesel which can be saved if 60 deg face model is used
= (Amount of energy associated) / (Latent heat of diesel)
= (74646.26 Joule) / (34.92 X 106 Joule/litre)
= 2.14 X 10-3 Litre/second
= 7.6 Litre/hour
4.5.5 Amount of fuel saved per km = (Diesel saved) / (Speed)
= (7.6 litre/hour) / (93.6 km/hour)
= 0.0899 litre/km
= 0.09 litre/km
Therefore 0.09 litres of fuel can be saved every kilometre the vehicle moves if we use a 60 deg
faced model for real buses and trucks.

16. 5. Conclusion
Thus, it can be finally concluded that we can save 0.09 litres of diesel if we manufacture a 60
degree faced bus or truck every km it moves with an average speed of 26 m/sec [93.6 km/hr].
A 60 degree faced automobile is quite feasible to manufacture with existing technology.
6. References
6.1 Anderson John D Jr, Fundamentals of Aerodynamics, Volume 3, McGraw Hill, New
York, 2001 : 6-9
6.2 Hypertextbook.com
<http://hypertextbook.com/facts/2006/TatyanaNektalova.shtml> : 12