Wind Tunnel Smoke Testing

[A2WindTunnel]

Porsche Cayman testin in A2WT.

http://www.youtube.com/watch?v=SoGHYDk44zA&feature=youtu.be

D

[manta22]

Smoke testing is entertaining but data is what is important. Is weight balance data recorded in these runs? Do you also do these tests at 5 degrees yaw angle?

Regards, Neil  Tucson, AZ

[A2WindTunnel]

Neil,

99% of the information we are interested in is contained in the data (drag, front downforce, rear downforce, front side force, rear side force, pitch moment, yaw moment, roll moment) that comes from the  loadcell-balance (under the floor).  Sometimes teams will let me post the smoke portion of the test session (video & or pictures) where we are not collecting data due to the fact that people are in the test section and would affect the numbers.  Teams pay for the data and don't want their data posted so we cannot put out their numbers.  I put out these videos because people on this site and others have emailed me with interest and enjoyment of just seeing the smoke over different cars. The majority of our customers will not let us post pictures or video of testing so this is only a few that let you guys catch a glimpse of what’s going on in the tunnel.   

Our AeroDyn tunnel can go out to 5-degrees of yaw if a team requires. Most first time uses will test in A2 because of the low costs associated but we do all the testing in A2 at 0-deg yaw (to save them money).  Typically most improvements you see at 0-degrees will carry out to yaw but if you are doing specific studies on end plates ect.. you would need to see how they react in yaw. Most landspeed cars have low yaw angles due to the fact that they travel very fast and the track would probably not be open if the cross winds were too high (so low cross winds).  Cars might see a max of 3 degrees yaw (depending on speed and cross wind).  Dose anyone know the max wind at the track they will allow before shutting down the race?

D

[manta22]

Thanks, D.

It might be a useful marketing ploy to post some actual test data taken on a popular street car (Corvette, rat rod, etc?) owned by one of your employees. Since it would not be paid for by a racing team it would not be proprietary and you could make it public. You could write off the cost of the test as an advertising expense as well. This data would show potential customers just what kind of detailed information that wind tunnel testing would give them.

As far as the yaw tests are concerned, I have copies of test data that was taken on a number of race cars (GT40, Porsche 917, etc) in the 200mph wind tunnel at MIRA in the UK. These yaw tests were done to investigate what the lift/downforce does when the car starts to get out of shape. If the lift increases under yaw, chances are that it is going to spin or at least contribute to instability at high speed.

Regards, Neil  Tucson, AZ

[A2WindTunnel]

As far as the yaw tests are concerned, I have copies of test data that was taken on a number of race cars (GT40, Porsche 917, etc) in the 200mph wind tunnel at MIRA in the UK. These yaw tests were done to investigate what the lift/downforce does when the car starts to get out of shape. If the lift increases under yaw, chances are that it is going to spin or at least contribute to instability at high speed.

Neil,

FYI: MIRA is only capable of 80mph (130kph) NOT 200mph. And what yaw angles are you talking about?  How much lift did they increase? Be careful not to assume other cars would show the same trends.

Testing for up to 5 degrees would show center of pressure but not lift off.  If it is a safety test for cars spinning then you would need a tunnel where the turn table could go to very high yaw angles and maybe even 180-degrees to map out in detail the yaw angle where the car would achieve lift off. Lockheed Martin in GA is the tunnel used by NASCAR for this study since their table is capable of 180-deg yaw.

It might be a useful marketing ploy to post some actual test data taken on a popular street car (Corvette, rat rod, etc?) owned by one of your employees. Since it would not be paid for by a racing team it would not be proprietary and you could make it public. You could write off the cost of the test as an advertising expense as well. This data would show potential customers just what kind of detailed information that wind tunnel testing would give them.

We are working on such a "project" and I hope to have something done this winter.  The short details are a car run at Loring or Ohio in a "stock" configuration and then develop in the wind tunnel and show a delta speed increase. There will be data, pictures and video of the entire project from start to finish.  I understand there is a lot of people that don’t know what a wind tunnel is used for or how to use effectively so my goal is to shed some light on wind tunnel testing and the benefits. Kind of a how to wind tunnel test 101. Thanks for the questions and the interest.

D

[Tman]

Thanks again for posting here!

[manta22]

D:

I don't think we are talking about the same MIRA tunnel. The present MIRA full-scale wind tunnel fans are shown on their web page

http://www.mira.co.uk/our-services/full-scale-wind-tunnel-(fswt)  You are right about the speed capability of this tunnel.

The one I am talking about is this one (photo below); as you can see, it does not appear to be the same tunnel. The data I have covers the 1969 to 1974 time period so that tunnel may have been shut down years ago. The fans pulled so much electrical power that it was only possible to operate it at night, after the town was in bed for that additional electrical load during the day would pull down the line voltage.

The tests were usually done at 0, +/-5, & +/-10 degrees yaw angle. One report states "Yawing the car does not increase drag but increases the lifting force (by 20% at 5 degrees yaw; by 80% at 10 degrees yaw), and causes an overturning couple."

Regards, Neil  Tucson, AZ

[WOODY@DDLLC]

Click on 1960: http://www.mira.co.uk/about-mira/mira-heritage#milestone_145

A2 makes 85 mph with 640 HP. Power is proportional to the velocity cubed so with 1960 efficiencies ~100+ mph? Not too bad for them days! 

[Jack Gifford]

D- Very informative thread. Thanks for posting. And wishing you much success.

[Jon]

Look forward to the A2 project, how are you going to give people the confidence that any improvements are from aero gains?

Top speed on a sealed mile would be dependant mainly on aero, hp and weight, to get a good handle on the effect of changing one the other two need to be unchanged.
Corner scales are easy, that leaves hp.
Not trying to be a pain but if your going to the effort it would pay to make sure people can't say "yes but".

There isn't a wind tunnel available where I am, the closest one is 21 hours drive away but I am looking forward to seeing the results.
jon

[A2WindTunnel]

Insert Quote
Look forward to the A2 project, how are you going to give people the confidence that any improvements are from aero gains?

Top speed on a sealed mile would be dependant mainly on aero, hp and weight, to get a good handle on the effect of changing one the other two need to be unchanged.
Corner scales are easy, that leaves hp.
Not trying to be a pain but if your going to the effort it would pay to make sure people can't say "yes but".

There isn't a wind tunnel available where I am, the closest one is 21 hours drive away but I am looking forward to seeing the results.

Good Question.  The plan is to run one day in the 1st configuration and then make all the aero changes the same weekend.  People would be welcome to keep an eye on me during this process to make sure nothing is touched in the engine or weight dept. Hopefully i can get a data logger to show shift points and RPM to make sure we are not sand bagging. Bonneville would be great for this because we will use a fairly low HP engine, but Ohio and Loring are the closest events.  There might be a part 2 in Bonneville but we will have to see how this project pans out from a funding stand point.

Dave

[A2WindTunnel]

Neil, Im pretty sure this is the same tunnel as in your old picture. Or is appears to be the same to me. I would imagine that there would be some differences in appearance from then and now with upgrades, but I think the fan arrangement is unique to MIRA.




http://www.reverie.ltd.uk/lotus_exiges2_windtunnel_01.php

[Freud]

A2......what a marvelous plan.

I think this will add a large measure of knowledge to most of us with little

wind tunnel knowledge and zero tunnel experience.

Apparently there are no prerequisites for Wind Tunnel 101.

THANKS.

FREUD