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Old 05-08-2020, 02:12 AM   #1 (permalink)
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A pillar guides

I noticed that there is flow separation near the A pillar on the side glass of my Gen 1 Insight. (Tufts angled upwards near the pillar.)



I wondered if I could do anything to fix this. I tried some aerofoil aluminium extrusion as a turning vane.



Unfortunately the material I have is in 290mm lengths. (It came with a small vertical axis wind turbine I bought.) I attached it to the A pillar with tape and wood spacers. Converging duct - outlet smaller than inlet.



I made a few adjustments and found it to work well. I used a whiteboard marker to show on the glass where the tufts were going with the turning vane (solid lines) and without the turning vanes (dotted lines). (Where there are only solid lines, there was no change.) Five tufts show much improved behavior, and one tuft slightly improved behaviour.



I then ditched the aerofoil and made some plastic guides out of PVC pipe sliced up, but results were poor.

I've looked to see if I can buy that extrusion by the metre, but for the life of me, I can't find it. So at the moment I am stuck.

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Old 05-08-2020, 05:34 AM   #2 (permalink)
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It's been a while since we have seen a tuft test.
You could try vortex generators, never seen or heard of them used on the door pillar.
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Old 05-08-2020, 08:36 AM   #3 (permalink)
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It looks like Honda did a good job with the mirror! My old Civic Wagon had a lot of turbulence behind the mirror. I like that your testing is on the same car I have!
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Old 05-08-2020, 12:30 PM   #4 (permalink)
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Quote:
Originally Posted by JulianEdgar View Post

I then ditched the aerofoil and made some plastic guides out of PVC pipe sliced up, but results were poor.

I've looked to see if I can buy that extrusion by the metre, but for the life of me, I can't find it. So at the moment I am stuck.
Just spitballing...

You could make a simple mold from the aluminum airfoil you already have. Then cast a airfoil in either silicon, plastic, foam or some other material.

Having it somewhat flexible would allow it to form to body panel curvature if need be. (within reason)



>
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Old 05-09-2020, 12:36 AM   #5 (permalink)
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So I thought the vortex generator suggestion was a good one. So I made some wedge-shaped vortex generators from small rubber door stops:



The tried them at different positions and orientations on the pillar:



and then the door frame:



Using these vortex generators I could certainly change the flow, and at times improve it (best results with vortex generators on the door frame).

But I couldn't get anywhere near the flow improvement I got with the aerofoil air curtain. So I might try going back to the PVC-pipe based plastic deflector and see if I can do better than I did with that last time.
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Old 05-09-2020, 03:23 AM   #6 (permalink)
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So I went back to the plastic guide I had made. Compared with the aerofoil:



You'd think that if the aerofoil were acting just as a simple guide due to its curvature, the plastic guide would work as well. But it doesn't*. I did further back-to-back testing and the plastic guide does basically nothing.

For testing it works really well having the wool tuft whiteboard marks on the inside of the glass: I put the aerofoil back on and the tufts returned to exactly their previously marked positions.

I then trialled just one 290mm long aerofoil and its nearly long enough to get the good behavior when it is positioned liked this:



The rubber vortex generators semed to work best on the low window tufts, so I may be able to use a mix of the 290mm aerofoil and the rubber vortex generators to get the attached flow I want.

(* I am starting to think that the Edgarwit's excellent performance is at least in part because of their true aerofoil shape. If you think of an aircraft wing's downwash, that airflow direction will help the Edgarwits guide flow back to the car body sides, and of course the same applies to these A-pillar air guides.)

Last edited by JulianEdgar; 05-09-2020 at 03:38 AM..
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Old 05-09-2020, 03:29 AM   #7 (permalink)
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I think this is the only real window pillar test I have ever seen in here.
So I think it's cool. Any improvement is likely a first.
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Old 05-09-2020, 03:47 AM   #8 (permalink)
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Quote:
Originally Posted by oil pan 4 View Post
I think this is the only real window pillar test I have ever seen in here.
So I think it's cool. Any improvement is likely a first.
I cover A-pillar treatments in my book, but that was for aero noise reduction. (Which should be analogous to gaining attached flow, actually.)

This is the first time I've tackled A-pillars myself.
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Old 05-09-2020, 11:14 AM   #9 (permalink)
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Wat I understand, relevant or not, is that the airflow on the bottom of an airfoil is typically always attached and laminar on a semi flat bottom section. Not so on the curved surface, and due to the lack of leading edge radius is probably turbulent as all get out probably to the point of stagnation.
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Old 05-09-2020, 01:37 PM   #10 (permalink)
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Quote:
Originally Posted by Piotrsko View Post
Wat I understand, relevant or not, is that the airflow on the bottom of an airfoil is typically always attached and laminar on a semi flat bottom section. Not so on the curved surface, and due to the lack of leading edge radius is probably turbulent as all get out probably to the point of stagnation.
Yes indeed - you’d expect an aerofoil to have much lower drag than a simple curved plate. But I am very surprised it appears to be so critical in this application. (Most turning vanes aren’t aerofoils.)

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