Does downforce increase when it rains?

[roon]

This is not a trick question.

[bhall II]

No, because the cars are slower, and downforce is proportional to the square of speed.

Next!

[DiogoBrand]

No, because the cars are slower, and downforce is proportional to the square of speed.

Next!

But does the air density increase to a point where it makes a positive difference in downforce, when speed, frontal area and Cl are mantained?

[bhall II]

All else being equal, humidity actually reduces air density. That said, precipitation may or may not have an effect on temperature and atmospheric pressure, which would also influence air density. But, I don't know enough about meteorology--or anything else, really--to know exactly how they're all tied together.

[Greg Locock]

Say 8 mm/hour in a heavy shower. so in an hour 2wideby 1 high sq m of frontal area drives through 1.22 *2*v*3600 kg of air in the dry, plus .008*1000*2*v*3600 of water in the wet

well that surprises me. Yes, at the same speed and wing setting.<-All wrong see next post

[Greg Locock]

No, that's wrong. the rain falling on the car is not affected by its speed, so a 10 sq m plan area car will see 80 kg of water in the rain, and at 200 kph 2 sq m will drive through 200*1000*2 cubic metres of air, which weighs 500 tonnes. so the answer to any practical extent is NO. Phew!

[hollus]

Rain tires are also larger. Everything else equal, this raises the floor and further reduces downforce.

[J.A.W.]

No, that's wrong. the rain falling on the car is not affected by its speed, so a 10 sq m plan area car will see 80 kg of water in the rain, and at 200 kph 2 sq m will drive through 200*1000*2 cubic metres of air, which weighs 500 tonnes. so the answer to any practical extent is NO. Phew!

Apologies Greg, for that -1, it is an error, I meant to upvote your post, but I don't know how to swap it..

I do think that there are many other variables, such as the lead car driving in rain only ( not spray ),
& making a path through the ground water, rather than running in the tracks pumped out by others..

[hollus]

https://www.dmcinfo.com/latest-thinking ... op-density

if you froze time and collected the rain inside one cubic meter of rainy air, you would have about 780 cubic mm of water, or almost a cubic cm.

My F1 car, which works in international units, runs through 200 cubic meter of air in a second (100 m/s), so it would intercept almost 200 g worth of water every second.

[Manoah2u]

downforce might increace theoretically, but grip is lost due to the water becoming an obstacle in contact of the vehicle with the ground (through the tyres),
so the possibly tiny effect that rain has on downforce is completely destroyed by the latter.

[roon]

Thanks, all. Greg, hollus, good posts. bhall, maybe the teams keep track of such weather conditions in the interest of how they will affect airflow & drag.

My assumption was that downforce would slightly increase, due to the weight of the rain drops increasing the mass of the air. Keep in mind that raindrops are also in free-fall, so it is not only that we should factor in their weight at 1g, but also their velocity. Thus you might say this slightly heavier air will be slightly heavier again. But the slightness of the slightly is probably very slight indeed.

There are other factors to consider, such as: does rain help or hinder flow attachment? Does rain influence vortex formation?

I wonder if teams have ever developed rain wings for rainy races. I assume suspension set up and wing angles at least get adjusted if rain is forecast.

Now, how about engine performance? I assume that, after the air filter, the rain is converted to mist or vapor. Unless the filter gets really soaked. Will more humid air help or hinder combustion, compressor and/or turbine efficiency?

Also, all the cars should be disqualified during rain races. Using phase change cooling media to aid radiator function is explicitly prohibited by the rules, yet each team does exactly this when drive their cars through the rain, and the rain hits the radiators. Kudos to the first team that takes advantage of this by seeing rain on the horizon, and deciding to pit the car before it gets wet. They would win that race on a technicality.

[hollus]

Think that drops do not flow like air, so they will not produce downforce by "flowing" around the wings or under the floor. They only add "downforce" by braking their downwards trip against the car (bus as Greg mentioned, speed doe snot help there) and by being deflected upwards (really, impact and deflection) by the wings. Only a small part of the car will do this, so you are likely adding only grams of downforce, in my opinion. The drop in air density (higher humidity, typically lower atmospheric pressure when it rains) will have an effect many times larger. IMHO.

[ETM]

All things equal, yes, downforce (and drag) increase in the rain. This is because it raises the fluid (air) density
represented by 'p' in the Lift coefficient and Drag Equations.

A more theoretical way to explain it is to apply Newton - For every action, there is an equal and opposite
reaction. The wings throw the air upward. The greater the density of the air the greater the force that is created.
It is why a car at sea level creates so much more downforce and less drag compared to a car in Mexico City, the
density of the air is higher at sea level.

[PlatinumZealot]

At topic. No. Rain is a extraneous material to aerodynamics.

[roon]

Aerosoldynamics, then?