Water tunnels in F1

[shelly]

The irony is that with 60% scale model and 250kph top speed F1 wind tunnel do not match real car's Reynolds number for speed greater than 150kph

[raymondu999]

So are you saying then, shelly, that a water tunnel would ironically be more accurate?

[shelly]

If you can push ater fast enough and overcome all the Big difficulties of working with a water tunnel it may be.
But F1 rules are water tight here, as they forbid also tricks like pressurized or cold air tunnels

[Richard]

Not forgetting the compressibility of water relative to air. That would make it hard to model the air expansion under the floor and diffuser.

[JohnsonsEvilTwin]

Not forgetting the compressibility of water relative to air. That would make it hard to model the air expansion under the floor and diffuser.

Hard but not impossible.

The main question really is what are the benefits for this with water when it can readily be achieved with air?
Seems water is an expensive and less effective way of doing things.

[shelly]

We can (most of the times) forget about that, as speed around the car is not that fast to get transonic effects.

Could be nice making as simulation in a water tunnel with a lighter fluid simulating exhausts.. but this is just dreaming

[Richard]

Hard but not impossible.

No. It would be impossible.

The compressibility the others have mentioned is in closed high pressure systems. Its not relevant to this application.

[JohnsonsEvilTwin]

Can a closed high-pressure system not be made relatively easily and adapted?

[Sonic59]

The irony is that with 60% scale model and 250kph top speed F1 wind tunnel do not match real car's Reynolds number for speed greater than 150kph

There are methodics, that increase effective reynolds number.

[Richard]

JET - We're talking about the pressure differentials from front to back of car, and top to bottom. That needs an open system for mass to flow from a high pressure zone to a low pressure zone.

...

Lets move on. What about the problem of cavitation ?

[czt]

I've not heard of f1 using smoke wands for flow visualisation, as described in the original post. Mostly you are lead by results but occasionally a brightly coloured liquids or tufts may be used to examine surface flows (or as mentioned earlier the more complex PIV system at toyota)

[PNSD]

Toyota wind tunnel (now used by Ferrari I think) has the capability for PIV, which is a wind tunnel technique that gives full flow field visualisation which can be put in direct comparison with pictures from cfd.
See here:
http://www.tecplot.com/Community/CaseSt ... veeng.aspx
I think for some time toyota's has been the only F1 wind tunnel with such capability (which needs a lot of extra machinery compared to a normal wind tunnel); I do not know if now some other team can do PIV (except from ferrari using toyota's knowledge, of course)

Few teams have tried to implement PIV which is why they have pretty much all gone to Toyota.

PIV is costly, and time consuming to setup. F1 teams do not have time. In the past they have paid for external companies to do such work, coming in, installing their equipment in the respective teams tunnel etc. But as I said, F1 teams can not afford the time or cost for such setups.

Only Toyota could, and only Toyota had the people I believe. However im sure situation has changed and teams do have the capabilities...

With regards to the topic, UK users will im sure heard of a company known as QinetiQ? They are from the aerospace sector. There was a rumour circulating that the Mclaren MP4-25 did indeed have some water channel testing done by these guys.

Water channel testing is not uncommon within the automotive industry due to the Reynolds number effects. Obviously wind tunnels can only run a certain sustainable speed and automotive models can only practically be a certain size meaning more often than not due to cost reasons it can be difficult to achieve complete similarity.... Hence the use of water channels.

With the compressibility, do we have an idea of the flow velocity entering the floor? That is where the peak velocity will be located, but I doubt that velocity will exceed mach 0.3 for most applications where the teams are interested in the flow features. For that reason I would assume compressibility is negligible for these cases.

[shelly]

The irony is that with 60% scale model and 250kph top speed F1 wind tunnel do not match real car's Reynolds number for speed greater than 150kph

There are methodics, that increase effective reynolds number.

Do you hin at pressure tempertaure changes to tweak Reynolds or other tricks such as boundary layer tripping?

[Sonic59]

The irony is that with 60% scale model and 250kph top speed F1 wind tunnel do not match real car's Reynolds number for speed greater than 150kph

There are methodics, that increase effective reynolds number.

Do you hin at pressure tempertaure changes to tweak Reynolds or other tricks such as boundary layer tripping?

No. I now at least one certain method: to give airflow start level of turbulence.

[PNSD]

F1 wind tunnel models already have pretty substantial BL trips anyway.