Introduction

1.1 Abstract

With the lights out on 20th of March, 2022, the Bahrain Gran Prix starts, indicating F1’s return to the “ground-effect era.” Ground-effect is an efficient way of obtaining downforce, but also a risky one. The start of application of ground-effect in F1 starts with Lotus 78, but Lotus applied ground-effect maturely in Type 79, their F1 racecar for the season of 1978, and it won Lotus the championship of that year.

1978 was a year when most of the constructors was already using downforce to make their car faster in the corners. In this period, downforce was crucial to the performance of a F1 racecar since the cornering of a car depends on the static friction force directed into the apex that the tyres could exert, which is equal to ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? , where ?is the coefficient of friction and N is the normal force the car exerts on the ground, equal to its weight plus its downforce. Since the friction coefficient could not be raised in a great extent, teams had to focus on how to raise the Normal force. And as raising weight increases rotational inertia of the car, the best choice to increase the friction to turn is always adding downforce. This is why increasing downforce was crucial to all F1 teams if their goal was to win.

There are various methods to increase downforce; however, the method to test how much downforce a racecar gains was primitive in the last century. The conclusions about whether a design was effective was mostly gained from running the car in actual races.

What Lotus came up with in the year of 1977, when Type 78 was first introduced, was making the bottom of their car resemble to an inverted airfoil as the ones applied on planes, and used a side skirt that extended on the bottom of each sidepod to seal the space between the bottom of the sidepods and the outside air. This is how this legendary car “flied” reversely on the ground and through the corners.

However, though Type 79 was proved to be a successful car for its innovation in ground-effect, as it was faster than every other car on the grid of 1978, relatively low data shows how much downforce exactly could it produce.

?????? As time went on, however, more developments are made in the area of aerodynamics in cars, which focuses on the drag force and downforce produced by air on a car, including more ways to test the downforce a car obtains, such as CFD simulation and wind-tunnel. Today, F1 cars are designed using both CFD simulations on computers and wind-tunnels.

?????? But in this experiment, I will focus on constructing a wind-tunnel that is grounded on common materials that are easily fetched, which could be copied at home rather than in any intricate labs.

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1.2 Experiment

The purpose of this experiment is to test the efficiency of the application of ground-effect on race cars compared to regular methods of obtaining downforce using a wind-tunnel that is possible to be constructed using common materials only. The model car will be put into a home-made wind-tunnel and each of the component of the model will be tested on its contribution to the over-all downforce the car gains. The proportion of each component’s downforce to the over-all downforce will be calculated to determine the effectiveness of the application of ground-effect in producing downforce of a racecar. It is true that modern F1 cars’ different parts cooperate with each other to increase the efficiency of each other to increase the downforce of the overall car or to decrease drag---for instance, floor tuning the flow above diffusors to increase rear stability---this is why a 1:20 scale model of a Lotus Type 79 is chosen---for its aerodynamic performance is easier to be understood and analyzed, as it is assumed that an old Type 79 is not strongly affected by such association between different external components and that the overall downforce of a Type 79 is simply the sum of downforce produced by each component. Since data on the Type 79 is not abundant, given its age, it is not possible to test whether the data on each part of the car corresponds to the actual car; rather, it is only possible to compare the results of the overall downforce of the model to that of the actual car to conclude whether or not this home-made wind-tunnel is valid in mimicking the aerodynamic performance of actual cars.

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Experimental Methodology

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2.1 Materials

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A U-tube ranging from 0 to 10,000 Pa

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Two hoses to connect the U-tube with the Pitot tube

Pitot tube

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Paper tubes (similar to those inside rolling-papers)

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Hard papers as materials for the wind-tunnel

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A hard board

A balance

3 fans with power of 45W

Goggles to protect forehead and eyes from cold wind coming out of the wind-tunnel