Artículo de CFD de la parte aerodinámica de un auto de carreras.

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Aerodynamic Effects on Formula One Car Using CFD
Article in International Journal of Applied Engineering Research · January 2015
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International Journal of Applied Engineering Research, ISSN 0973-4562 Vol. 10 No.33 (2015)
© Research India Publications; httpwww.ripublication.comijaer.htm
Aerodynamic Effects on Formula One Car Using CFD
a
Raj Kamal M.D b
Socrates.S c
Kaliappan S
a b
Assistant Professor, Department of Mechanical Engineering, Velammal Institute of Technology, Chennai-601204, India
a
kamalaerodynamics@gmail.com, b Socs.mech@gmail.com
c
Associate Professor, Department of Mechanical Engineering, Velammal Institute of Technology, Chennai-601204, India
a
kaliappa@yahoo.com
Abstract
The Aerodynamics of the Formula Car is an important parameter. At a speed of about 70
kmph aerodynamic drag exceed to 50% of the total resistance to motion and above 100 kmph, it
is the most important factor in the aerodynamic point of view. The Formula Car has to produce
the necessary Down force so as to stick to the ground during the turns. The main objective of
this project is to Study the effect of the Dimple on the Front Wing Surface of the Formula Car.
This improves the Down force produced by the car.
Key words: CFX Software, Down force, Dimple
1. Introduction
Down force is Force acting on the car toward downward direction, created by
the aerodynamic characteristics of a car. The purpose of down force is to allow a car to travel
faster through a corner by increasing the vertical force on the tires, thus creating more grips.
Since down force is the requirement inverted aerofoil‟s are used to produce the required down
force and in some cases augmented with flaps to gain more down force.
The amount of down force created by the wings or spoilers on a car is dependent
primarily on two things:

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 The shape, including surface area, aspect ratio and the thickness of the profile preferably 12-
15% of the chord (low speeds)
 The device's orientation (or angle of attack)
Fig 1. Forces acting over inverted aerofoil Fig. 2. Placement of flap to main wing
Profiles used to create down force:
 Front spoiler
 Rear spoiler
 Diffuser
Spoilers:
A spoiler is an aerodynamic device whose intended design function is to 'spoil'
unfavorable air movement across a body of a vehicle in motion, usually described as drag.
Spoilers are often fitted to race and high-performance sports cars, although they have become
common on passenger vehicles as well. Spoiler is used to control the dynamics of handling
related to the air in front of the vehicle. This can be to improve the drag coefficient of the body
of the vehicle at speed, or to generate down force.
Front spoiler
This is placed in the foremost of the car to produce down force and also deflects the air
above the wheel, which is most drag producing part of the car. Front spoiler vary in design
complexity from simple chin spoilers to the beautifully shaped air dams, now integrated into
road car designs and extended in dimensions and effectiveness on competition cars. The down

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force produced by the front spoiler gives more traction to the front wheel thereby giving is
better turning characteristics.
Fig. 3. Front spoiler of Ferrari f1 car Fig 4. Flow over spoiler without and with endplates
Rear spoiler
The rear spoiler is placed at the rear of the driver and at a height that is above all the
disturbances created by the profiles of the car in front of it. The rear spoiler plays an important
role in producing down force and also counters acting the moment created by the front spoiler.
The down force produced by the rear spoiler is greater than that of the front spoiler so that a
greater amount of traction resulting from the down force is given to the rear wheel which
powers the car; hence there is better power transmission from the wheels to the road.
2. CFD
CFD is a technique of replacing Partial Differential Equations governing the fluid flow
by a set of algebraic equations and solving them using digital computer.
Any fluid flow in the universe is governed by a set of equations. The equations are the
governing equations,
 Continuity Equation.
 Momentum Equation.
 Energy Equation.
Governing equations in partial differential form
Continuity equation

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The continuity equation in algebraic form is given as,
ρ1 A1V1 = ρ2 A2V2
The continuity equation in integral form is given as,
𝜕
𝜕𝑡
𝜌𝑑𝑣𝑣
+ 𝜌𝑉. 𝑑𝑆𝑠
= 0
The continuity equation in Partial Differential Form is given as,
𝜕𝜌
𝜕𝑡
+ ∇. 𝜌𝑉 = 0
Momentum equation
𝜕
𝜕𝑡
𝜌𝑽 𝑑𝑉𝑣
+ 𝜌𝑽. 𝒅𝑺 𝑽𝑠
= - 𝑝 𝒅𝑺𝑠
+ 𝜌𝑓𝑑𝑉𝑣
+ F viscous
Energy equation
𝑞𝜌𝑑𝑉𝑣
+ Q viscous - 𝑝𝑽. 𝒅𝑺𝑠
+ 𝜌 𝒇. 𝑽 𝑑𝑉𝑣
+W viscous =
𝜕
𝜕𝑡
𝜌 𝑒 +
V2
2𝑣
𝑑𝑉+ 𝜌 𝑒 +
𝑉2
2𝑠
𝑽. 𝒅𝑺
The energy equation in partial differential form is given as,

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3. Design of Aerodynamic Components
The primary objective of the aerodynamic components is to provide high turning at exiting
speeds and diminishing drag produced by the formula car. As mentioned earlier, aerodynamics
is often the factor that gives a race car, an edge over its competitors.
The following components are employed to bring about the desired aerodynamic efficiency.
It is important to note that the term „spoiler‟ in automotive parlance, generally refers to the
aerodynamic wing and/or flap incorporated to produce down force (negative lift).
Front spoiler
The front spoiler is the first component of the car that meets the oncoming air. Therefore it is
imperative that the wing makes utmost use of the air.
The first step involved was to define the workspace where the spoiler is to be placed.Confining
to regulations, there were 76 cm of space measured from the outer edge of the front wheel
available to make the spoiler. Further, the regulations restrict any part of the car, outstretching
the front two wheels. This meant the spoiler cannot be any wider than 120 cm. A 6 cm
clearance was provided to the wheel from the whole front spoiler arrangement, for it to steer
safely.
The most important restriction was the ground clearance. Every car needs to maintain at least
1.5 inch (about 3.81cm) of ground clearance at static conditions. Since the suspension was set
to travel 1 cm, the ground clearance for this car have been demarcated at 5 cm from the ground.
Thus, a workspace has been defined to fit in the front spoiler.
Magnus effect:
Non-symmetric flows about a spinning body, such as a cylinder or sphere, immersed in a
viscous fluid, causes generation of an aerodynamic force, normal to the body‟s angular velocity
vector.

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This phenomenon is known as Magnus Effect, which is in accordance with Bernoulli‟s
Principle. This side force could be lift or downforce depending on the direction of the free
stream and the rotation of the body. However, enormous drag is caused due to Magnus Effect,
since the spin and the subsequent perpendicular force causes significant turbulence in the wake
of the body.
In a race car, which is required to be operated in “open wheel” condition by the FSAE, the
Magnus Effect is a huge deterrent. This effect considerably destabilizes the laminarity of the
flow and also causes huge drag. Hence, it is of top priority that Magnus Effect is curtailed.
Multi-element aerofoil:
The Magnus effect comes into play when the spinning body is immersed in a viscous fluid.
Therefore, this effect can be diminished by restricting the fluid from enveloping the body, i.e.
by scooping the air over the wheel, such that it circumvents the wheel.
Thus, a multi element aerofoil [wing + flap(s)] shall serve two prime purposes, that of,
producing maximum down force and minimizing the drag due produced by wheel due to
Magnus Effect.
A very important factor to be noted is that, FSAE race cars operate at relatively low speeds than
formula car. A three element aerofoil (wing + 2 flaps) was originally considered for the front
spoiler. But in such low subsonic speeds, the chances of the third element becoming redundant
were quite high. Hence a two-element aerofoil, i.e. a wing and a flap arrangement was deemed
fit for the front spoiler. Here, the wing creates downforce and the flap adds on to the downforce
and as well as diminishes Magnus effect.
Specifications of wing and flap:
Wing - Chord – 51 cm - Angle of attack - 7°

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This angle of attack is an optimization on the l/d characteristics of the aerofoil and also the
appropriate angle for the flap.
Flap - Chord – 23 cm- Angle of attack - 15° (with respect to the first element)
The flap does not run uninterrupted, as it has to be cut where the nose of the car appears. Also
the flap should not obstruct the incoming flow to the Side pods, which is paramount. Ergo, the
flap was given a suitable wingspan that shall encompass the wheel but shall not perturb the
flow to the Side pods. The span of the flap is measured from the endplate.
The vertical aero foils were based at the centre of the wheel (10 cm from its edge) and its angle
of attack deflected the air outboard.
Model 1 Model 2
Fig 7. Front Wing Without Dimples Fig 8. Front Wing Dimples
The Dimensions of the Dimple are 2cm in Main Wing and 1cm in the Flap.
4. Results
The Results of the CFD Analysis of the Front Wing with and without dimple is made at various
velocities and results are compared.

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Fig 9. Pressure Contour Plot of Front Wing Fig 10. Velocity Contour Plot of Front Wing
Fig 11. Comparison Chart Between Down Forces Fig 12. Comparison Chart Between Drag
Forces
V. Conclusion
The results discussed in the above section shows the increment of the Down Force for the
Same Dimensions with the Dimples. An average of 15 % improvement in Down force and L/D
is shown from the results. Further work can be done by implementing the same to the Rear
spoiler.
References
[1] Joseph Katz., Race Car Aerodynamics, Bentley Publishers, 1995.
[2] Simon Macbeth., Competition car Aerodynamics, Haynes publishing, 2006.

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[3 Nigel Macknight., technology of the f1 car, Hazleton publishing, April 2002.
[4] Enrico Benzing., Ali wings, Giorgio nada editore, 28 April 2012.
[5] David Tremayne., Science of the Formula Car, J H Haynes and co limited, 2009.
[6] Anderson, John D., Jr.: Fundamentals of Aerodynamics, 3d ed.,McGraw-Hill,
New York, 1991.
[7] Anderson, John D., Jr.: Computational Fluid Dynamics, McGraw-Hill, New York, 1995.
[8] Gou Peng-fei., Front Wing design of Formula SAE racing car based on Computational Fluid
Dynamics, April 2011
[9] S. Mahon, X. Zhang and C. Gage., the Evolution of Edge Vortices underneath a Diffuser
Equipped Bluff Body, University of Southampton
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