BACKGROUND

The Gold CREST application is linked to a STEM competition called "F1 in schools". I have been participating for the last 3 seasons.

The purpose of the competition is to design and race a model F1 car, made of composite materials and propelled by a CO2 cartridge.

There are 3 classes in the competition, the level of engineering getting harder as you progress.

My role in the team is design engineer and team leader. Unfortunately, my other 2 teammates do not want to apply for the award, so I

am applying on my own by presenting my individual projects in this year's event.

Although the purpose of the competition is not to race the fastest car, it is the secret ambition of every team!

Due to the various COVID lockdowns it became clear to me that the competition would suffer from the constraint on resources. Namely time

(working as a team with regular meetings and tasks), money (No fundraising possibilites)

and resources (materials, manufacturing facilities etc., also linked to lack of funds.)

To achieve this ambition, you can work on 2 aspects (given that the propulsion method and power is the same for all cars) :

- optimise the aerodynamics of the car

- minimise the weight

My aim was to study and develop a strategy around the aerodynamics and weight of the car to decide which was the most important within

the race track, and I set myself the following objectives:

1. Understand the principles of aerodynamics and apply them to the design of the car

2. Optimise theoretical knowledge in order to minimise costly manufacturing mistakes and wasted time

3. Document in an analytical way the approach and the results

Manufacturing?

PRINCIPLES OF AERODYNAMICS

In previous seasons, the design of the car focused on respecting the competition rules and regulations without a real understanding

Final car design on Autodesk Inventor

of the airflow over the car and its impact.

In order to gain theoretical knowledge on the subject, I read the following books :

- Race Car Aerodynamics (revised 2nd edition), by Joseph Katz, Bentley publishers, 2006

(concepts of drag, viscosity, wake, Reynolds number, Venturi effect)

I used this book to calculate the reynolds number of the rear wing, see below in section 'rear wing design'

and to observe the venturi effect, see below in 'Wind tunnel'

- Computational Methods for Fluid Dynamics (3rd edition), by J.H. Ferziger and M Peric, Springer Publishers, 2002

(concepts of airflow, boundary, turbulence and mathematical formulae for virtual testing using computer software)

I used this book to interpret the results of the wind tunnel tests, see below in section 'Wind tunnel'

For Gantt Chart

- How to Build a Car by Adrian Newey, Harper Collins Publishers, 2017

(critical insight into F1 car design problem solving)

- McLaren MP4/4 1988 (all models) owners' workshop manual, Haynes Publishing, 2018

I used this book to gain insight into the limitations of both theoretical design and practical testing and to help me eliminate variables

(teamwork, time and resource constraints, creativity)

F1 season race analysis

F1 youtube channel

In order to understand my approach to the design, let's describe a few key concepts of aerodynamics :

An object moving through air at speed compresses the air molecules in front of it (high pressure), making it harder to go fast (think of

walking against the wind). It also pushes the air molecules outwards (its wake), creating a vacuum/low pressure behind it. This is

called drag and slows the object down (think suction cup).

The higher the velocity of the object, the stronger the forces to hold it back (every F1 engineer's nightmare).

As the car has limited energy (CO2 cartridge), the challenge is to create an aerodynamically efficient car. This is to transfer the most

Tear drop shape

energy into speed, by making the cross-sectional area of the trailing edge (last point air is in contact with the car) as small as possible

Reason why so efficient

to reduce the drag.

tuna shape

car teardrop shape

Teardrop Caravan History - Find Out How It All Started (kupler.eu)

Top view of airflow

Submarines

high pressure

low pressure

side view of airflow over cube (not

aerodynamic !)

Daimler Truck AG on Twitter: "Check out this amazing 1959 Mercedes-Benz 190 SL #teardrop restauration by @ALL190SL What a spectacular car! #Mercedes #MercedesBenz #cars #car #classiccars https://t.co/HddTnKFYUS" / Twitter

(photos courtesy of Computational methods for fluid dynamics)

REAR WING DESIGN

Benz ‘Tropfenwagen’ (sportscardigest.com)

From the above, it is apparent that the rear wing of the car is going to create a lot of drag as it is the last point of contact of the air with

F1 cars have a rear wing to create downforce (opposite of lift) and drag, which enables them to corner at higher speed, to the

detriment of velocity in a straight line.

The F1 in schools racetrack is a 20m long straight line, therefore the rear wing is not needed. However, the regulations insist on

including one, the challenge is to make it as aerodynamic as possible, with as little drag as feasible.

Rear wing was useless

I have looked at 3 main aspects to reduce this :

- angle of attack : I have set it at 0°, for the wing to present the smallest profile possible, which in turn creates less low pressure

- shape : the most aerodynamic shape in the world is the teardrop, as it has the smallest Reynolds number.

F1 car use rear wing for downforce

The Reynolds number records how effectively a shape is moving through a fluid (air is seen as a fluid), as per the following equation :

Some of the first f1 cars were teardrop shaped but wings and regulations changed that

Re = VDρ/μ

Critique of teardrop, cannot use on big scale and why don’t use in f1 and f1 in school

where Re is the Reynolds number, V is the fluid velocity, D is the characteristic linear dimension, ρ is the fluid density and μ is the

dynamic fluid viscosity.

I have calculated the Reynolds number of the rear wing to be :