The document discusses the significance of vehicle aerodynamics in enhancing performance and fuel efficiency, emphasizing the shift towards computational fluid dynamics over traditional wind tunnel testing. It outlines a project aimed at reducing the aerodynamic drag coefficient of a car through design modifications, detailing methodology, simulation results, and the effectiveness of these changes. Findings indicate substantial reductions in drag and lift for a modified Audi car model, enhancing both fuel efficiency and vehicle stability.

2. ABSTRACT
• Now a days with an increase in competition,the vehicle
aerodynamics plays an important role.
• Aerodynamics affects the performance of vehicle due to change in
parameters such as lift and drag forces which play a significant role
at high speed and fuel economy.
• With an improvement in computer technology, manufacturers are
looking toward computational fluid dynamics instead of wind
tunnel testing to reduce the testing time and cost.
• Our project main aim is to reduce aerodynamic drag coefficient by
improving the design of a vehicle, which is possible by placing
scuttle in front and change the modification on rear bulk head and
varying the angle between the rear under body and base of the car
body. It make the car safer and make it fuel efficient.

3. INTRODUCTION
• Automotiveaerodynamics is the study of
the aerodynamics of road vehicles. Its main goals
are reducing drag and wind noise,
minimizing noise emission, and preventing
undesired lift forces and other causes
of aerodynamic instability at high speeds.
• Air is also considered a fluid in this case. For
some classes of racing vehicles, it may also be
important to produce down force to improve
traction and thus cornering abilities.

4. Introduction
• Drag is a force that acts parallel to and in the same direction
as the airflow. The drag coefficient of an automobile measures
the way the automobile passes through the surrounding air.
• Downforce is the vertical component of the aerodynamic
forces acting on the car. As the car travels through the air, the
downforce will push the car down into the ground.

5. Literature review
• Sneh Hetawal et al. [1] 2014
• This article describes the design and CFD analysis of a
Formula SAE car. A numerical study of a rear engine
SAE race car is presented. The focus of the study is to
investigate the aerodynamics characteristics of a SAE
race car with front spoiler, without front spoiler and
with firewall vents. The aerodynamics study of the SAE
car is made to reduce the drag force. The study was
performed using the CFD package. The main goal of
this study is to enhance the stability of the vehicle and
reduce the drag. With this the track performance will
be increased also the resistance of air to the vehicle
gets reduced.

6. Literature review
• S.M. Rakibul Hassan et al. [2]2013
• By study of this article we have observed 50 to 60% of total
fuel energy is lost due to this aerodynamic force. This
article is concentrated on different aspects analysis of
aerodynamic drag of racing cars and different drag
reduction techniques such as rear under body modification
and exhaust gas redirection towards the rear separation
zones. The drag can be reduced up to 22.13% by different
rear under-body modifications and up to 9.5% by exhaust
gas redirection towards the separated region at the rear of
the car. It is also evident that if somehow the negative
pressure area and its intensity at the rear of the car can be
minimized, the separation pressure drag is subsequently
reduced.

7. Aim and objective
• The aim of project is reduce the drag force
and improve the down force of audi car
model.
• Prepare the car model
• Run the CFDF simulation
• Re design the car model for reduce the drag
• Comparison between original and modified
car model.

8. Problem identification
• Drag is the aerodynamic force that opposes the
motion of a car as it moves through the air. It's
caused by the friction and pressure differential
between the air in front of the car and the air
behind it.
• Minimizing drag is essential for achieving higher
speeds and improving fuel efficiency. Cars with
lower drag coefficients (Cd) experience less
resistance and can move more efficiently through
the air

9. Methodology
• The car model is done in the solidworks. The
solid works is the user friendly software. The
3D model id taken from the internet source.
• Some little modification , model is executed.
In the work, only car body is considered, with out wheels.

10. methodology
once the model is done, the model is imported into the ansys 17.0 version.
Here the geometrical errors are cleared.
The body is complex shape model so, the tetrahedron element is used to mesh the
mesh. In the analysis the model has 152635 elements and 162582 nodes.

11. methodology
• The boundary condition are considered.
Which are inlet, outlet and car wall.
• From the inlet, the air is enter into the
domain, from the outlet the air exit from the
domain and wall is taken on the car body, due
to this drag and down forces are calculated.

12. methodology
• K-E turbulence model is used.
• Air and its properties are considered in the
analysis.
• Inlet air velocity is taken as 80 and 100 kmph.
• Drag and down force is selected.

13. methodology
• Once work has done on the original model,
the front portion of car is edited to improve
the down force and reduce the drag force.

14. Finite element model.

15. Velocity distribution on car at 80 kmph

16. Results/ pressure distribution on car at
80kmph

17. Velocity distribution on car at 100
kmph

18. 100 kmph speed

19. Modified results at 80 kmph

20. Modified model pressure and velocity
at 100 kmph

21. Results and discussion
S.NO Speed
(km/hr)
Existing car body Modified car body (%)of drag
reduction
1 80 0.348 0.224 35.63
2 100 0.357 0.311 12.88

22. Results and discussion
S.NO Speed
(km/hr)
Existing car body Modified car body (%)of lift
reduction
1 80 0.43 0.277 35.33
2 100 0.464 0.443 4.52

23. Scope
• Similar kind of experimentation can be performed
for different profiles at different orientations and
different air flow velocities. By changing the air
flow velocity for a particular profile at different
design, average static pressure and drag force can
be calculated and can be validated by conducting
the experiments using the wind tunnel of
different test section sizes. This study can be
performed for any kind of car profile of a four-
wheeler and which will helps us to reduce the
effect of drag and increase the vehicle stability.

24. CONCLUSIONS
• By the simulation results on both existing and
modified car design, the modified car has less
drag and less average static pressure when
compared with that of existing design of Audi R8
at a given angle and speed.
• The minimum drag observed after developing the
front and rear modifications on car body.
• Thus our design gets less turbulence leading to
the increase in fuel efficiency and vehicle stability.

25. References
• James Keog, Tracie Barber, Sammy Diasinos, Doig Graham, Aerospace Engineering Department,
California Polytechnic State University, School of Mechanical and Manufacturing Engineering,
UNSW, Australia-2016.
• Alamaan Altaf a, Ashraf A. Omar b, Waqar Asrar Department of Aeronautical Engineering,
University of Tripoli, P.O. Box 13154, Tripoli-Libya -2014.
• Sneh Hetawala, Mandar Gophaneb, Ajay B.K.C, Yagna valkya Mukkamalad a, b, c, Second year
M.Tech. (Automotive Engineering), School of Mechanical and Building Sciences, VIT University,
Vellore, Tamilnadu, India. d Professor, Thermal and Automotive Division, School of Mechanical and
Building Sciences, VIT University, Vellore, Tamilnadu, India. 2014.
• D.E. Aljure a , O. Lehmkuhl a, b , I. Rodríguez a , A. Oliva a, a Heat and Mass Transfer Technological
Center (CTTC), Universitat Politecnica de Catalunya-BarcelonaTech (UPC), ETSEIAT, Colom 11, 08222
Terrassa, Barcelona, Spain b Termo Fluids, S.L. Av. Jaquard, 97 1-E, 08222 Terrassa, Barcelona, Spain
2014.
• CFD modelling of the aerodynamic effect of trees on urban air pollution dispersion J.H. Amorim, V.
Rodrigues, R. Tavares, J. Valente, C. Borrego CESAM & Department of Environment and Planning,
University of Aveiro, 3810-193 Aveiro, Portugal 2013.
• S.M. Rakibul Hassan, Toukir Islam, Mohammad Ali, Md. Quamrul Islam Department of Mechanical
Engineering, Bangladesh University of Engineering and Technology, Dhaka-1000, Bangladesh 2013.