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Old 06-23-2021, 04:22 PM   #1 (permalink)
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DARKO / A2 Wind Tunnel

In the now-closed thread: ' Why don't vehicles have aerofoils...', at # 201 (permalink) Julian Edgar returned to disparage the DARKO Wind Tunnel once again.
1) DARKO was a 'curved-wall' wind tunnel.
2) According to Hucho, test vehicles, in excess of 20% blockage return perfectly acceptable drag coefficients if tested at zero-yaw, and if a blockage ratio calibration model, tested in a large-scale wind tunnel is employed in data reduction.
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3) From the video ' Streamlined Toyota T-100 in Wind Tunnel', anyone may observe that I personally moved the smoke wand to the ceiling of the DARKO tunnel, expressly to demonstrate that there was no constrainment of the streamlines, as might be feared in a 'small' wind tunnel.
4) Anyone may also notice that DARKO has no provision for yaw testing, only zero-yaw.
5) Anyone who read the report about the DARKO testing, is also familiar with the fact that a Toyota Full-Scale Wind Tunnel Blockage Calibration Model was used in advance of the T-100 testing at DARKO.
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6) With respect to the A2 Wind Tunnel, it is of an 'adaptive-wall' design with movable test-section surfaces.
7) Models used within 'adaptive-wall' wind tunnels may have blockage in excess of 30% and return perfectly acceptable Cds according to Hucho, as long as tested at zero-yaw, and with a blockage ratio calibration model from a large wind tunnel.
8) Any observer of the A2 Wind Tunnel will immediately notice that it has no provision for yaw testing.
9) The same large-scale blockage-ratio calibration model as used by Don Sherman et al., in the CAR and DRIVER 'Drag Queens' article, from the A2 Wind Tunnel is the same calibration model as used for Spirit of EcoModer.com at DARKO.

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Old 06-23-2021, 04:30 PM   #2 (permalink)
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It's not hard to understand. The smaller the wind tunnel, the less it can be relied on for accuracy.

Every credible technical reference states that; to suggest otherwise is simply to mislead.

It's the major reason why no major car manufacturer, race team, etc, uses small wind tunnels to test full-size vehicles. Instead, they spend hundreds of millions of dollars building huge wind tunnels.

This isn't a new idea - Volkswagen built their full-size wind tunnel in 1966.It had a 5 per cent blockage factor.

I won't bother contributing further to the thread: night doesn't become day just because someone here says so.
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Old 06-23-2021, 05:00 PM   #3 (permalink)
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wind tunnels

Quote:
Originally Posted by JulianEdgar View Post
It's not hard to understand. The smaller the wind tunnel, the less it can be relied on for accuracy.

Every credible technical reference states that; to suggest otherwise is simply to mislead.

It's the major reason why no major car manufacturer, race team, etc, uses small wind tunnels to test full-size vehicles. Instead, they spend hundreds of millions of dollars building huge wind tunnels.

This isn't a new idea - Volkswagen built their full-size wind tunnel in 1966.It had a 5 per cent blockage factor.

I won't bother contributing further to the thread: night doesn't become day just because someone here says so.
1) there's context associated with 'small'. Curious that you don't recognize that when it's dropped directly in your lap.
2) you've dodged an explanation for curved-wall tunnels.
3) you've dodged an explanation for adaptive-wall tunnels.
4) you've dodged an explanation for using 'any' wind tunnel for iterative testing of the same vehicle under different body configurations.
5) Sad that Hucho's textbook has been downgraded to uncreditable.
6) Would you like to tell us the size of the actual air jet inside those 'huge' tunnels. Do you actually believe that what you see is all test section jet?
7) Does Volkswagen test at yaw angles?
8) Do you think the frontal area of a Vanagon Westfalia Campmobile and Cd 0.51 might have some bearing on the jet size requirement and yaw-testing area consideration of a wind tunnel design. And underutilization of same tunnel, when smaller test vehicles are inside?
9) How about size requirements for a passenger car towing a caravan RV travel trailer? And it's wastefulness when testing smaller vehicles?
10) You have a track record of dodging direct questions. The implications aren't pretty.
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Last edited by aerohead; 06-23-2021 at 05:03 PM.. Reason: add datatypo
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Old 06-23-2021, 05:00 PM   #4 (permalink)
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Round 4?
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Old 06-23-2021, 05:37 PM   #5 (permalink)
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Quote:
Originally Posted by oil pan 4 View Post
Round 4?
Sadly I'm getting to the point where I'm just putting people on my ignore list so I don't have to read through fights that go back and forth forever and ever.
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Old 06-24-2021, 09:58 AM   #6 (permalink)
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Sadly I'm getting to the point where I'm just putting people on my ignore list so I don't have to read through fights that go back and forth forever and ever.
How did you get that ignore function to actually work?
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Old 06-24-2021, 11:53 AM   #7 (permalink)
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Can you still tell what's going on, let alone find this thread, by what other posters quote from the ignore list?
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Old 06-24-2021, 01:32 PM   #8 (permalink)
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I click on the "name" of the person. Then "public profile." Then "user lists". And finally "add to ignore list" or something like that.

Sometimes you can see what's being said because of the quotations. But at least it makes the whole thread a lot shorter and cleans up some of the unnecessary.

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