Correlation between CFD and wind tunnel results

[miqi23]

Unless someone can explain why.

RANS can not predict drag accurately, that is why.

That is subjective!

Ask a passenger car manufacturer and they would be like, yes, we are with in 2 to 3% of the wind tunnel drag but the lift is off by 200%!

Aircrafts, well they are generally very close to lift figures but are in a constant struggle to get the drag right.

Remember, its always the smaller number that is difficult to get right which is obvious and obviously it also depends on how competent your engineers are! Its not what CFD is or is not capable of, its how you understand and use it properly.

[PNSD]

I guess the simplistic explanation would be that CFD predicts viscous effects, and effectively boundary layer development will be based on this. Pressure forces are something which CFD can do well, so for bluff bodies, CFD can be OK in terms of Cd.

[xpensive]

Does anyone have accurate numbers on how much fan-power you need run these monsters, my guess would be several MW?

[hardingfv32]

The Swift Tunnel in San Diego, CA area was required to operate in low demand time periods so as not to upset the local grid.

Brian

[xpensive]

I've searched the web for power figures without any luck, but judging from the length, flow and speed in these tubes, we might be talking tens of MW, an insane waste of energy and another argument against the aerodynamic age of Formula One.

Again, can anyone confirm any hard numbers?

[PNSD]

Ok, not F1 wind tunnels but still useful;

https://maiserxx.esss.lu.se/press/docum ... wagner.pdf

http://www.nasa.gov/centers/glenn/about/fs05grc.html

[Jersey Tom]

I've searched the web for power figures without any luck, but judging from the length, flow and speed in these tubes, we might be talking tens of MW, an insane waste of energy and another argument against the aerodynamic age of Formula One.

Again, can anyone confirm any hard numbers?

Everything in F1, the sport itself, is a "waste of energy" and "waste of money." It's a lavish expenditure for our entertainment. Nothing more, nothing less.

Want the series to be more energy efficient? Reduce the engine size / output to about 100hp so we're not burning so much fuel over the course of a race.

Besides, if it wasn't the energy bill of a wind tunnel that money and energy would just be spent elsewhere.

[xpensive]

Thanks for sharing the philosophical part JT. Now does anyone have any serious power numbers, is it 10 MW or 100 MW?

Christ, these are power-station figures, 10 MW is like 20 F1 engines on full song running around the clock?

[FW17]

How long does each wind tunnel session last?

[Pierce89]

How long does each wind tunnel session last?

Before the RRA they ran wind tunnels 24/7 in factory teams.
Now 40 hrs a week balanced against 60 tera flops(or whatever unit it is) of CFD a week
If you mean single run, then only long enough to get a small time averaged measure in each position tested. So, a few minutes of run time then a break to change configuration or reprogram ride height actuators etc.

At least, thats how it went when the owner of the Dirt Late Model I worked on took me to A2(smaller, much fixed floor tunnel owned by Aerodyne) with him.

[xpensive]

If a wind tunnel is indeed powered by 10 MW, 40 hours means 400 000 kWh.

Per week.

Insane.

[Just_a_fan]

I've searched the web for power figures without any luck, but judging from the length, flow and speed in these tubes, we might be talking tens of MW, an insane waste of energy and another argument against the aerodynamic age of Formula One.

Again, can anyone confirm any hard numbers?

Everything in F1, the sport itself, is a "waste of energy" and "waste of money." It's a lavish expenditure for our entertainment. Nothing more, nothing less.

Want the series to be more energy efficient? Reduce the engine size / output to about 100hp so we're not burning so much fuel over the course of a race.

Besides, if it wasn't the energy bill of a wind tunnel that money and energy would just be spent elsewhere.

I agree JT. Indeed, I've pointed out on a number of occasions that F1 is a waste of energy / resources and the whole "being green" thing is ridiculous when the whole thing is anti-green by its very definition.

But it's fun to see the anti-aero brigade saying that aero (and hence wind tunnels) are a waste of resources but flying the teams around the world and then running the cars around a track 20 times a year somehow isn't a waste of resources.

[FW17]

How long does each wind tunnel session last?

Before the RRA they ran wind tunnels 24/7 in factory teams.
Now 40 hrs a week balanced against 60 tera flops(or whatever unit it is) of CFD a week
If you mean single run, then only long enough to get a small time averaged measure in each position tested. So, a few minutes of run time then a break to change configuration or reprogram ride height actuators etc.

At least, thats how it went when the owner of the Dirt Late Model I worked on took me to A2(smaller, much fixed floor tunnel owned by Aerodyne) with him.

So once the model is put in, the tunnel is run for a few minutes so that the air flow is mapped in all areas of the car.

Then the model is changed, i guess.

1) So why should it run 24x7? Do teams make so many models?

2) What is the axis of rotation on the rolling road? can it rotate both horizontally and vertically?

[Pierce89]

Before the RRA they ran wind tunnels 24/7 in factory teams.
Now 40 hrs a week balanced against 60 tera flops(or whatever unit it is) of CFD a week
If you mean single run, then only long enough to get a small time averaged measure in each position tested. So, a few minutes of run time then a break to change configuration or reprogram ride height actuators etc.

At least, thats how it went when the owner of the Dirt Late Model I worked on took me to A2(smaller, much fixed floor tunnel owned by Aerodyne) with him.

So once the model is put in, the tunnel is run for a few minutes so that the air flow is mapped in all areas of the car.

Then the model is changed, i guess.

1) So why should it run 24x7? Do teams make so many models?

2) What is the axis of rotation on the rolling road? can it rotate both horizontally and vertically?

Rolling roads are not very adjustable AFAIK(only tunnel I've visited was fixed floor with a suck and blow boundary layer removal system)

As far as running 24/7 before the RRA, they weren't nearly as efficient in tunnel testing as they are now(more adjustability and more accutrate measurement now). They got less data out of a given timed run, so it took many more tests to go through a given amount of development part. So, they just kept the tunnel going till they tested every idea in their precious little heads(not to mention the overall moneyburning between 2004 and 2009)

edit: I somehow managed to reverse the names on the quotes

[FW17]

any video of actual testing process, with flow mapping and air speed/pressure mapping?