Maximizing ratio Cl/Cd


#1

I need to create a car which maximize the ratio Cl/Cd, so the purpose is to generate much more down force than drag. And every time I add elements to get down force I also get more drag, so I cannot get more than 1 in ratio. What would you do to maximize the ratio? How it should be the profile of the car? I´ve been doing some models, here you have some of them

https://www.simscale.com/projects/AlvaroML/supperi_403/
https://www.simscale.com/projects/AlvaroML/f1_honda_rst/

Regards, and thank you in advance


V70


#2

Hi @AlvaroML!

I am sure that the @PowerUsers_CFD or @Anware can help you here! Also tagging our race car simulation enthusiast @yosukegb4 who has plenty of experience!

All the best!

Jousef


#3

Hi @AlvaroML!

Wow where do I start? Maximizing the CL/CD ratio of a race car is kind of the goal of all aerodynamic work related to the car. There are so many considerations in balancing your drag vs your downforce from your front wing geometry, to the diffuser, to the shape of the body, rear wing etc etc. There is a lot of testing involved to achieve maximum performance from the car so if you’re looking for a definite answer to this, its a huge scope to cover.

From what I can input now off the top of my head is probably with regards to ride height. Lowering the chassis as close to the ground as possible would generate significant downforce for little change in drag, namely making use of ground effect. Ensuring that the flow at the floor doesn’t “leak” out the side as much as possible is also a way to maximize this effect.

There are plenty of more talented and experienced people around to help you with this and I hope to embark on a similar project like yours soon! Hopefully my earlier statement wasn’t incorrect :stuck_out_tongue:

Cheers.

Regards,
Barry

P.S F1 design books and looking at why certain designs are done in a certain way will certainly give you great ideas. Look there for inspiration and ways to optimize.


#4

Your statement sounds great. Thank you for the advice. I will look for some ideas on Internet and books in order to get the car ready for next week.

Cheers
Regards, Álvaro


#5

Let me just quote here a paragraph from Tune to win by Carroll Smith:

However, optimum aerodynamic efficiency is not the end of the down force question. Two other factors are even more crucial —keeping the downforce balanced between the front and the rear wheels and figuring out what to do with the down force.

Having said that, there are possibly other questions which might need to be answered first. For instance,

  • What are the constraints of the design? F1’s are the best they could get within the constraints of their technical regulations. When given freedom, F1 designers come up with completely different concepts —the Aston Martin Valkyrie or the Red Bull X2010.
  • Global dimensions and materials. From what I see in your projects; the dimension of the models is about 20 cm long. That’s roughly 1/20th of the size of an actual vehicle; so you might want to consider the implications this has on the flow like the transition from laminar to turbulent flow. Also, from the rough features I see, am I right in assuming you are considering to build a wood/plywood model or your design and test it? Otherwise, you could have thinner and or more streamlined endplates and features.

The more we know about your goals, the better we can assist you.

Cheers,


#6

This is a project for university, We have some rules
For example, the distance from one wheel to the other is 160 mm and the minimum distance from the floor is 8 mm. So having these dimensions in mind, we have to create the car a run a simulation at 1.6667 m/s.
The goal is how to create the best profile which maximize the ratio Cl/Cd. For that reason, I am having troubles with the proper shape of the car.

Thank you for the reply

Cheers, regards


#7

Hi @AlvaroML

I simulated some formula car aerodeveices in my project and reported them.


I hope they will be helpful.

If your regulations allow shapes other than formula styles,
the Le Mans prototype shape is generally more advantageous in L/D than formula style.

Regards,
Yosuke Yamamoto