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Originally Posted by Leafy
(Post 1201862)
From that first set of images it looks like the strakes need to extend in front of the start of the diffuser. And thats on a car that already has a flat floor. Imagine how much of a disaster it looks like on a car without a flat floor.
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It looks to me like the cell size for the simulation might not be small enough to pick up the thin walls of the diffuser. I can't see how that air could flow across the back like that.
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Maybe, but you'd think someone making a model that good would know to use automated mesh control to set a minimum wall thickness and pick those up. Or just use a dense enough mesh if whatever they were using didnt support that.
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Originally Posted by Leafy
(Post 1201886)
Maybe, but you'd think someone making a model that good would know to use automated mesh control to set a minimum wall thickness and pick those up. Or just use a dense enough mesh if whatever they were using didnt support that.
Still that flow looks very wrong for some reason. If the air was really flowing past the verticals then you would surely see very high pressure zones under each. Maybe there is a large gap to the ground where the air can cross but the whole point of those fins is to prevent that happening. If the sim is correct why have the fins at all? |
What I was pointing as is that, thats a pretty nice solid model. Its just surprising someone is able to make something that nice on the model side but then not do something fairly simple like that, or even fail to catch it when just looking at the results. It really does look like the sims are ignoring that the strakes even exist.
Theres some other oddities, like how the flow separated on the inside of the tires without significant turbulence. And there's also quite a few surface errors as well which certainly arent helping. Looking closer I dont think this is a solid model, I think someone scanned this in. |
Originally Posted by Leafy
(Post 1201909)
What I was pointing as is that, thats a pretty nice solid model. Its just surprising someone is able to make something that nice on the model side but then not do something fairly simple like that, or even fail to catch it when just looking at the results. It really does look like the sims are ignoring that the strakes even exist.
Theres some other oddities, like how the flow separated on the inside of the tires without significant turbulence. And there's also quite a few surface errors as well which certainly arent helping. Looking closer I dont think this is a solid model, I think someone scanned this in. It looks ok but I know from my sims you sometimes need to bulk up the thin walls up to bigger than your cell size otherwise with the size of the cells let the air through like they are permeable. |
Originally Posted by 1993ka24det
(Post 1201861)
So I was looking around again at diffuser designs and I seen what slimjim8201 wrote on f1technical.net.
Interesting data on Straight, convex and concave diffusers. Each are tested at 5, 10 and 15 degs. https://www.miataturbo.net/attachmen...ine=1422740199 Bearing in mind the data reservations above, should I be pencilling a concave, or a convex, shape? |
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Saw the Silver-Car at the MSX yesterday. Was surprised to see these roof rails feeding the rear wing:
https://www.miataturbo.net/attachmen...ine=1424610790 The car has a DTM type flat bottom/rear diffuser and fiberglass skirts in addition to the wing. One of the tech guys said they saw significant gains with those roof fins during their wind tunnel testing, and they made it on to the final version of the production car. That thing weighs 900 lbs and has 200HP... |
Originally Posted by Supe
(Post 1208532)
Saw the Silver-Car at the MSX yesterday. Was surprised to see these roof rails feeding the rear wing:
https://www.miataturbo.net/attachmen...ine=1424610790 The car has a DTM type flat bottom/rear diffuser and fiberglass skirts in addition to the wing. One of the tech guys said they saw significant gains with those roof fins during their wind tunnel testing, and they made it on to the final version of the production car. That thing weighs 900 lbs and has 200HP... |
One the K1, those double as a swan neck wing mount. In the Silver-Car, the wing mount is separate. These are only for guiding airflow.
That car is rear engine and has a firewall behind the driver, so visibility is moot anyways in this case. It also doesn't extend all the way down the rear body work, it was about 4" deep after the immediate roof line. I understand it can act as a safety feature if sliding sideways, but I wonder if extending them to the leading edge of the wing provides benefits similar to spill plates on a splitter. |
Looking at this picture, the roof fins make sense. The roof has a nice gentle slope to "put the air back together" and feed air to the wing, but I'm sure the air gets super dirty once it drops over the edge onto the rear hatch window. The roof fins should help keep the air from the sides of the car from spilling in. Seems like just raising the wing up into cleaner air would have been more effective, though.
https://silvercarusadotcom.files.wor...fromtibet1.jpg |
many racing bodies don't allow the wing to be higher then the roof.
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OGRacing, what wing are you running 200 or 300?
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i got the 200. i am about to raise it to the roof line.
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Mazda Skyactive Diesel Dive Planes
https://www.miataturbo.net/attachmen...ine=1427148200 Mazda Skyactive Diesel Side https://www.miataturbo.net/attachmen...ine=1427148200 Prototype Corvette powered Rear Diffuser https://www.miataturbo.net/attachmen...ine=1427148200 |
Awesome pictures. Interesting step in the wing. I would think that the purpose there is to slow down the air and create a higher pressure differential between the top and bottom of the wing.
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That is a pretty serious gurney on the Ferrari.
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it's interesting to see that the ferrari and DW almost don't want the high pressure air in the center of the splitter. the DW is flush with the front of the bumper, and the ferrari have big gaps. wonder why?
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The DW doesnt appear to want the drag, and the ferrari seems more concerned about getting as much air to its underbody aero as possible.
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