Aquaplaning & Downforce

Here are our CFD links and discussions about aerodynamics, suspension, driver safety and tyres. Please stick to F1 on this forum.
mzivtins
mzivtins
8
Joined: Wed Feb 29, 2012 11:41 am

Aquaplaning & Downforce

Post

If we say that water is roughly 800 times denser than air would this mean that if an f1 car had 800 times the downforce, it would eliminate Aquaplaning? and also eliminate the need for wet tyres altogether?

Roughly, at what condition does the density of water start to lift a tyre off of the floor?

Just a thought experiment, it seems obvious now, but water is such a huge force to deal with :o

MadMax
MadMax
4
Joined: Sat Oct 22, 2022 2:23 am

Re: Aquaplaning & Downforce

Post

The issue isn't, I think, the density of water but rather its incompressibility and its viscosity. Aquaplaning occurs at a given speed for a given tyre and is because the tyre's design doesn't allow the water to get out from under the tread blocks quickly enough, and then doesn't allow it evacuate from the grooves quickly enough (the latter issue being the driver as the water can't get out of the way of the tread block if the channels are full of water).

The ability of the tyre to move water is governed by the tread's design, the shape of the contact patch, the depth of the grooves (so how worn the tyre is), and the tyre's inflation (which affects contact patch shape, of course). Under inflating a tyre will cause aquaplaning to occur at a lower speed (all other things being equal), for example.

If water were compressible, aquaplaning would be less likely because water could be forced out of the way by compressing it. If water had a lower viscosity, aquaplaning would be less likely because it would flow out of the way easier.

User avatar
Big Tea
96
Joined: Sun Dec 24, 2017 7:57 pm

Re: Aquaplaning & Downforce

Post

As the water gets between the tyre and the road rue to the wheel 'laying' the tread ontop of the water, does viscosity or density have ant baring?

It is not something being 'scraped', it has to be actually shipped through the tread channels after being squeezed into them. A lower density or viscosity would be les effort to bet out would it not?
When arguing with a fool, be sure the other person is not doing the same thing.

TimW
TimW
31
Joined: Thu Aug 01, 2019 6:07 pm

Re: Aquaplaning & Downforce

Post

Aquaplaning is the formation of a full lubrication film between the the and the road. The front of the rolling tire forms a wedge shape to the road. In this wedge pressure builds up. If the pressure builds up enough, a film will form, and if the film is thick enough, the peaks of the tarmac will lose contact with the tire.

More downforce will postpone aquaplaning, but not with enough speed it will occur.
There is no air density that makes aquaplaning theoretically impossible. A car fully underwater can still aquaplane theoretically. The rolling tire will still try to build a film.

The pressure gradient required to push the water out of the wedge will depend on speed, viscosity and density. So a lighter fluid and lower viscosity will postpone film formation to a higher speed. But also air film bearings do exist.

Water lubricated rubber bearings are actually a thing used for ship propeller shafts etc. Rubber against a hard smooth surface is quite good for film formation.

Greg Locock
Greg Locock
225
Joined: Fri Jun 29, 2012 11:48 pm

Re: Aquaplaning & Downforce

Post

For a given tire the dominant effect on aquaplaning speed is pressure, but weight also has an effect. Depth of water also affects the onset.

TimW
TimW
31
Joined: Thu Aug 01, 2019 6:07 pm

Re: Aquaplaning & Downforce

Post

And the roughness of the road surface

CMSMJ1
CMSMJ1
Moderator
Joined: Tue Sep 25, 2007 9:51 am
Location: Chesterfield, United Kingdom

Re: Aquaplaning & Downforce

Post

If you had very narrow tyres then the force applied to the road (and through the water) would be significantly increased. That is if you had the same downforce.

You'd have less grip due to less area of lovely sticky mu on the floor - but the risks of the water being deep and dense enough to aquaplane would be slim to none..

SO - are we waying we need slimmer tyres with taller blocks to ensure running, at reduced pace, in any condition?
IMPERATOR REX ANGLORUM

Greg Locock
Greg Locock
225
Joined: Fri Jun 29, 2012 11:48 pm

Re: Aquaplaning & Downforce

Post

yup, narrow tires, deep grooves, lots of them, high pressure. The problem with deep grooves is that the rubber flexes a lot and so tends to overheat easily.