[Maximoose]

Hi there, I am 13 years old an am competing in the F1 in Schools challenge this year, which is where you design, analyse, and make a F1 style car to race at a competition. I have made a CAD model in Inventor 2019 and am wondering if it is aerodynamic or not, and if not what I can improve.



Thanks in advance!

[FMDenaro]

Nice to see such an young boy starting to be engaged in aerodynamics flow problems!


At your level of study is difficult to go in deep in the aerodynamics problems, I will try to give some points based on the physical aspects


1) in regions where the velocity of the flow decreases you get higher pressure values of the air. This is relevant in the design of the wings for aerodynamics load
2) Do not think that a car must mimic a missile geometry. The velocity of a car (max 300-350km/h) is limited to subsonic conditions, there is no supersonic peak.
3) think about the weiight of the car. The more you add as wing the more it is.
4) think about the resistence of the air. The more is the surface exposed to the air the more is the resistance to the movement.
5) Usually the wheels are bigger at the rear part of the car.


Good luck

[Maximoose]

You have given me some useful pointers, but I am not sure how to incorporate them into the design. Could you tell me what areas I need to improve and how I might do this? Also we're not allowed to modify the wheels

Also I ran a CFD Simulation in Flow Design, and I got a drag coefficient of 0.18. Is this good?

[FMDenaro]

Originally Posted by Maximoose

You have given me some useful pointers, but I am not sure how to incorporate them into the design. Could you tell me what areas I need to improve and how I might do this? Also we're not allowed to modify the wheels

Also I ran a CFD Simulation in Flow Design, and I got a drag coefficient of 0.18. Is this good?

Forget the number you got from the simulation... to have a realistic value the simulation requires to be much more sophisticated that you can immagine.


Try to see a real F1 car and try to deduce the improvement you can introduce in your model.

[JBeilke]

Just have a look at the lift coefficient. You want to create a downforce and you have to make sure, that the front wheel stays on the street, even when your car slightly changes the distance to the ground.

Avoid situations like this:

https://www.youtube.com/watch?v=mBu8p7RCsF8

[CeesH]

I agree with Filippo that to compute the drag coefficient accurately is difficult, it requires accounting for a lot of small details.

But in any case, you have produced quite a streamlined model, which will generally give low drag coefficients (the range 0.2-0.3 is quite typical for highly streamlined production cars).
F1 cars, however, rarely have low drag coefficients - they may be as high as 1.3!

The reason for this is the enormous amount of small wings and flaps all over the car. These are designed to produce downforce - which means they push the car down against the road. The benefit of this is that the car can go through corners much faster, without "flying out of the corner". This is reflected in the lift coefficient JBeilke mentioned; you want that to be high. The downside is that it also produces a high drag coefficient, which slows down the car at the straights. For F1, the tracks are typically quite curvy, so teams aim at maximizing downforce (lift), even if that increases the drag - speed in corners is more important than on straight lines, and on the straight line, the extremely powerful engine helps them a lot. Of course, the very best engineers are masters at maximizing the lift while keeping drag as small as possible - but drag will always be much higher than for street cars.

One of the practical things in your design currently, if you want to look at drag: the back of your car is flat. This means a large "pocket of air" is dragged along behind the car (the wake), which increases the drag. If you can, minimize this.

[Maximoose]

Thank you for the reply. I will try and make the back more rounded and send a picture back to you. I also modified the wing to face at a 30 degree angle. My thinking behind this is that it will allow the air to flow over the wheels, as they are a point in the design which will cause a lot of drag. Could you please confirm my thinking?

[Maximoose]

With regards to your point about the back being flat, sadly we are not allowed to modify that part of the car as per the rules and regulations. However, I have a new image of the car with a new wing design. The idea of it is to let the air flow over the wheels, rather than heading straight in and causing more drag.


Thanks again for the help you have given

[CeesH]

Hi,

Wheels are notoriously draggy parts of the car, so directing the flow around it seems like a good idea. But the front wing has many more purposes; one is generating downforce itself (pushing the nose down at the road to avoid the car from taking off), another one is directing air to other parts of the car where downforce is generated.

Did you read the following pages?

https://www.totalsimulation.co.uk/se...le-front-wing/

[FMDenaro]

I would not design such a front wings as they appear ... they will add more and useless weight

[CeesH]

Indeed, keep it thin to avoid weight! What you also can see with F1 front wings is that they curve upward; the first part is nearly parallel to the road, and only the back points up. They do that with many different elements nowadays, which is much too complex for a school assignment, but you can take the same general shape. (like this one: https://commons.wikimedia.org/wiki/F...2009_Japan.jpg)

Be careful with the angle of the back part, don't make it too large! If you do, there will be a pocket of air behind the wing (like with the back) which will make it lose downforce!

[FMDenaro]

I would use much more slender front wings but having small winglets

[Poryongming]

F1 in schools is just a drag race down a straight 20m track. Cars are tethered by a nylon string to the track.
Therefore
1. Cars do not need downforce
2. Cars have to be as light as possible

Cars have to conform to a set of regulations which specify things like size of wings and wheels etc

What you should do is
1 DO NOT model your car on real F1 cars
2 Do look at previous F1 in schools cars for ideas
3 Make sure you follow rules. Eg you need an exclusion zone behind the front wheels. Make sure the wings are not too thick

You have not addressed pressure drag behind the rear wheels. Put in fairings behind the rear wheels and your cd will immediately drop

[Maximoose]

I've updated my model with quite a few major changes

[Poryongming]

That looks good but bear in mind that your front wings need to be 20mm wide. Make sure they follow specification, including thickness etc also.

In your updated model they look as wide as the wheels, which are usually about 15mm wide.

Your rear wheel fairings seem to end rather abruptly. Remember they are meant to taper gradually so as to minimise boundary layer separation and turbulence.