1. In what ways can Team Automaestro utilize the laws of aerodynamics to
enhance the performance of their formula student car? Describe five car
components that you would use for this purpose. [15]
Ans:
From the laws of aerodynamics like the continuity equation and
Bernoulli’s equation we know that - (i) if the area is increased then the
velocity of the fluid decreases (the continuity equation) and (ii) if the
velocity of the fluid decreases the pressure of the fluid increases there
following the Bernoulli’s principle.
Team Automaestro can use these laws to reduce lift force, to increase the
downward force, to reduce air resistance or drag force resulting in overall
increased performance, higher speed, better fuel efficiency, better grip and
faster cornering.
If the velocity of the airflow can be increased under the car while reducing
its velocity over the car then according to Bernoulli’s principle, it will create
a high-pressure zone just over the car and a low pressure zone under the
car. This will decrease the lift force and create downforce. The less the lift
force, the safer the car will be at high speed cornering. The increased
downforce also helps here by increasing lateral tire grip.
Five car components that can be used for this purpose:
1. Spoiler: It is a component used to change or spoil the airflow above,
around and underneath the car to reduce wind resistance, drag and lift
force which ultimately increases the cars control. It cannot create any
additional downforce but its reduced lift helps the driver to gain more
control as the wheels are in contact with the road more firmly.
2. Wing: It is a very important aerodynamic component for a formula
student car as it actually creates additional downforce because of its
reverse airfoil shape. Thus, resulting in better grip, more control and
stability.
3. Undertray and Diffuser: Undertray maintains high velocity low pressure
air under the vehicle and diffuser reduces the velocity of this air before
meeting with high pressure air that flows over and around the car.
4. Front splitter: It manages the air flow in front of the car and creates
downforce on the front section of the car’s body resulting in firm grip for
the front wheels.
5. Sidepods: They allows the airflow to go around the wheels to prevent
turbulence and also redirects the air through the radiators, break ducts
for efficient cooling,
2. Describe the four aerodynamic forces that act upon a car. How do the
effects of these forces differ for an airplane and a formula car? [10]
Ans:
The four aerodynamic forces that act upon a car are Thrust, Drag, Lift
and Downforce.
Drag: Aerodynamic drag is the force that the oncoming air applies on the
car, opposite the direction of the car’s motion, making it hard for the car to
move forward. It is the air resistance on the cars body. There are two types
of drag- frictional drag and pressure drag. Pressure drag is more prominent
than frictional drag at high speed. The more abrupt shape the cars body is
the more drag force the car will face.
Lift: It is the force that acts in the upward direction and opposite gravity
which tries to lift the car from the road. Lift force generates from the
pressure difference of under and over the car. This force has a strong
effect on car stability, high speed cornering and lane change
maneuverability. Lift force tends to flip the car over during high-speed
cornering, so it is tried to be kept minimum.
Downforce: Downforce is the vertical force that acts upon the car which is
not because of the car but because of the air flowing around it.
Downforce is the most important aerodynamic force that
a car faces. Though increased downforce creates a huge amount
of drag force on the straights, this really helps to plant the car
to the road at corners offering the driver with better handling
as this increased downforce counters the centrifugal force
created while high-speed cornering.
Thrust: Thrust is the main driving force of a vehicle. It comes from the
power generated by fuel consumption in the engine and transmitted to
the wheels through gear mechanisms.
In an airplane the thrust force works similarly to a car. In both cases the
thrust force drives the vehicle or aircraft forward. The effect of drag
force is also similar in these two cases as it works in the opposite
direction of the plane or car’s movement and tries to slow it down.
But the lift force has the opposite effect on a plane and a car. For an
airplane lift force is the desired force and it is tried to be kept
maximum. But for a car lift force is undesired and is tried to be kept
minimum.
For a car the downforce is very useful as it offers faster cornering and
better handling. On the contrary, for an airplane this downward force
adds to its weight and the more a plane weighs the more fuel it
consumes.
3. Explain the function of an undertray and diffuser. How would you design an
undertray and diffuser for the fs car of Team Automaestro. [10]
Ans:
Undertray and diffuser are often considered a combined component. It
is an aerodynamic component that uses ground effect (a venturi-like effect
under the vehicle) to create lower pressure under the vehicle and higher
pressure on top resulting in downforce. Efficient underbody diffuser
produces maximum down force with minimum or negligible drag. Though wings
produce greater amount of downforce than undertray diffusers, the wings
of the car have to work with lower speeds and have to be larger resulting in
significant amount of drag and weight addition due to the low top speed of
formula student cars.
The diffuser slows the air flowing under the car and thus reduce it to free
stream to make a laminar transition of the air at the end of the car when
two airstreams (one from under the car and one from top) meet. This
subsides the drag and increases the overall undertray efficiency.
If I were to design and undertray and diffuser for the fs car of team
Automaestro, I would consider these things to minimize the drag and
maximize downforce:
1. Ground clearance: For large ground clearance, the cross-sectional area
would not change much and so the velocity of air would be almost constant
in the intake section. So small ground clearance will allow the air to move
faster. But if it is too small, the undertray will produce positive lift
because there will be almost no airflow between the undertray and the
ground and there will be a high chance of the undertray hitting the road
if the surface of the ground is to be irregular and thus causing damage to
the components. Therefore, I would keep the ground clearance not too
small nor too big. 40 mm would be good enough as according to rules it has
to be minimum 25.40 mm.
2. The angle of the diffuser: If this angle is close to zero, the air speed will
not be reduced enough and if this angle is very large, the boundary layer
flow will detach and the airflow will be turbulent under the diffuser. Both
of these cases will lead to a huge amount of drag. So, I would keep the
outlet angle moderate to ensure minimum drag to downforce ratio. In a
research (reference-7) the optimum angle was found 21 degree.
3.
Isometric View
Outlet
Inlet
Right Hand Side view
Top view
4. One of the aerodynamic components of an FS car plays an important role in
cooling the engine. Explain its functionality in detail. [15]
Ans:
The aerodynamic component that also works in cooling are
sidepods. They are located in either side of the car’s cockpit extended to
the rear wheels and help to shape the airflow around the car which in turn
increases the car’s overall performance. Sidepods play a crucial role in
cooling the car’s engine, transmission and brakes. They are equipped with
radiators, oil coolers and brake ducts that helps to dissipate heat.
Sidepods are also shaped to maximize the amount of air that enters the
car’s cockpit to keep the driver cool and comfortable.
As the car moves at high-speed air is displaced by the wheels and creates
turbulence behind the car resulting in increased drag. The sidepods are
thus designed to guide the airflow around the wheels and into the car’s
diffuser. A very popular configuration of sidepods now-a-days is the coke
bottle sidepods which are shaped like a bottle and tapered inward to
reduce drag. Fin-like vortex generators are placed on the sidepods to
create small vortices of air which help to control the airflow over the
surface of the sidepods reducing drag and increasing performance.
Sidepods are the main source of heat rejection for the power unit. Their
design allows the air to flow through the radiators and oil coolers in a
very efficient way.
5. What is the significance of side skirts in race car aerodynamics, and how do
they contribute to reducing drag and enhancing lateral stability?[10]
Ans:
Side skirts are used to prevent the airflow from getting under
the car from the sides. Side skirts are flat surfaces extending from the
undertray on both sides of the car. Side skirts are similar to undertray as
both works using the ground effect. Undertray maintains high velocity low
pressure air under the car. But the high-pressure air on both sides tries
to get into this low pressure zone and if this happens then the effect of
the undertray is ruined as the air will become turbulent under the car and
thus creating a huge amount of drag. Side skirts prevent the side airflow
to go under the car and maintain the pressure difference.
Side skirts also enhance the lateral stability of the car by creating
downforce on both sides and increasing overall downforce.
As shown in the picture the side skirts created downforce which will counter the
centrifugal force generated while cornering. Thus, the car will have firmer grip on
the road and better handling while in a very fast cornering.
6. What are the primary considerations in designing a race car's body planes,
and how do they impact front-end grip and overall vehicle balance? [10]
Ans:
1. The car’s body planes must be designed in such a way to ensure that the
car’s center of gravity remains as low as possible because high center of
gravity will tend to topple the car over while turning or cornering. Low
center of gravity gives the car more stability and control.
2. The front splitter is a key component in a car’s body for better front-end
grip. It manages the airflow and creates downforce on the front side of
the car and thus giving the front wheels more traction and grip.
3. Weight distribution of the car has to be done properly because if in some
area the weight is way too more than some other area the car will be
unbalanced. This can be solved by increasing downforce on those
underweight areas and decreasing downforce on those overweight areas
by installing some aerodynamic components or shaping that areas body
planes likewise so that the overall weight distribution remains good.
4. The car’s body planes have to be designed using aerodynamic concepts so
that the outer surface of the car’s body creates minimum amount of drag
and cuts through the air more easily. Otherwise the huge amount of drag
produced at high-speed will pull the car backward and consume a lot of
fuel.
5. The car’s body planes must be able to manage the airflow properly and
pass the flow through radiators and oil coolers for efficient cooling.
7. How have recent advancements in materials, such as carbon fiber
composites, glass fiber influenced the design and effectiveness of race car
aerodynamic components?[10]
Ans:
1. Advanced carbon fiber or glass fiber materials are very light weight than
traditional materials that were used to build car body parts. As we know
the more the weight of the car the more fuel it consumes. So these light
weight materials can really increase fuel efficiency and offer better
maneuverability.
2. These advanced carbon fiber materials also offer high structural
strength and stiffness. So, complex shaped aerodynamic components
made of these materials can be installed on the cars which are able to
withstand more pressure and force than traditional steel or aluminum
made components.
3. These advanced carbon fiber composites or glass fibers are highly
customizable meaning they can be easily molded and shaped into very
complex designs which are nearly impossible with traditional materials
without losing their structural integrity. So, with these materials new and
more effective aerodynamic components are being introduced which will
result in more effective airflow management and overall enhanced
performance.
4. If the outer surfaces of the car’s body planes are made of these
advanced carbon fiber materials, then they can be made smoother without
significant surface imperfections which the traditional materials cannot
offer. And as smoother outer surface means less drag, less turbulence
and eventually better fuel efficiency.
5. These materials also can absorb more force and pressure than traditional
materials. So, in case of crushes or accidents body parts made of these
materials will reduce the damage of impact and offer more driver safety.
So, the properties of these advanced carbon fiber or glass fiber materials
has started to influence the designs of race car aerodynamic components
making them better, stronger and more efficient.
8. CFD is a very important part of designing aerodynamic components. Which
CFD software will you use to run a CFD simulation that can give accurate
results and will be capable of handling the heavy computations related to it?
What challenges will you face translating simulation results to real-world
performance?[20]
Ans:
There are several CFD simulation software in the market. Some best
CFD softwares are:
1. Ansys Fluent: Its CFD simulations offer high computing power, little to no
error in results, advanced meshing features and have been validated for
their quality.
2. Autodesk CFD: This software offers in-depth insights into a fluid flow
with minimum requirements for physical prototypes. It also allows CAD
modification and simplification.
3. SimScale: It is a web-based software so it works in any web browser
online. So, it removes the limitations of having low spec hardwares.
There are other CFD softwares like CFD Module, Simcenter, Flowsquare,
Paraview etc. But I prefer Ansys Fluent to run CFD simulations as it is one of
the most popular and user-friendly softwares.
Though the advantages there are some challenges while translating
simulation results into real-world performance.
1. The result may not be accurate if enough parameters and data sets are
not given and also because of simple flow models or simplified boundary
conditions.
2. Translating virtual simulation results into real world experimental results
can be quite hard because during the simulation one has to consider and
apply all the parameters of a real-world experiment. Mistaking some of
the variables and conditions can lead to faulty results.
3. Some simulations need a lot of parameters and conditions and to get the
proper result these simulations have to compute a lot of things which will
demand high-spec hardwares and may consume a lot of time.
4. CFD softwares have many built-in models into them and they use and
compare these built-in models to the given parameters and conditions to
predict the result of the simulaitons. But its very unlikely that these
built-in models will match 100% with the real-world scenarios which
eventually brings the question of these simulations’ accuracy.
5. CFD somftwares use mesh feature to compute the results of any
simulation. Mesh feature works by dividing the whole model into small
sections and thus computing applied parameters and effects on these
small sections to provide the overall simulation result. So insufficient
mesh refinement or faulty meshing can lead to errors in the result.
Reference:
1. https://www.nationwidevehiclecontracts.co.uk/blog/the-science-behind-car-design-how-aerodynamics-affectsperformance#:~:text=The%20reduction%20in%20drag%20can,such%20as%20handling%20and%20acceleration.
2. https://www.researchgate.net/publication/289714840_Aerodynamics_and_aerodynamic_research_in_Formula_1
3. https://www.f1technical.net/features/21555
4.
5.
6.
7.
8.
9.
https://www.cars.com/articles/what-does-a-spoiler-do-424902/
http://what-when-how.com/automobile/vehicle-drag-automobile/
https://www.mercedesamgf1.com/news/feature-downforce-in-formula-one-explained
https://ijret.org/volumes/2015v04/i11/IJRET20150411035.pdf
https://formulapedia.com/side-pods-f1-car/
https://www.formula1-dictionary.net/side_skirts.html
10. https://youtu.be/IlmVow4Kl7Y