Quote:
Originally Posted by JulianEdgar
Think of the same process occurring, but this time on the upper surface of the car, eg over a curved rear hatch (so of course giving lift not downforce). Now make that upper surface have a massive pressure drop, such that flow wraps around from the side to the top surface, so creating strong vortices. Clearly lift will increase a lot. But so will drag! Drag doesn't matter much in racing cars, but concerns us.
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Probably so! The diffuser angles in the article are much higher than typical road cars, up to 20 degrees, and at much lower ride heights.
Quote:
Originally Posted by AeroMcAeroFace
I think the confusion arises because the video omits the large vortex that forms in a diffuser that only has side strakes, maybe because that vortex is much smaller or irrelevant in a diffuser with many strakes. Or maybe it is beyond the scope of the video
"The video specifically states that the strakes and their tip vortices separate the flow coming off the rear wheels from the rest of the diffuser, at 7:44." They probably do, maybe that is not the only benefit though.
"He also says several times (and takes as his initial premise) that the vortices rolling off the strake edges stay at those edges," Well, there is a vortex that stays at the edge, he omits the massive vortex that forms though (see first paragraph)
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But if it's the large vortex that is responsible for the downforce generated by these diffusers, wouldn't it be important to mention that? He says he has another video on diffusers, maybe he does there.
Quote:
Originally Posted by AeroMcAeroFace
"The video also asserts that the vortices rolling off an L-shaped vane occur at the tip of the horizontal portion, but images in the article show the opposite--the vortices roll up the opposite side from the L." as I said in the previous post "The last image (in the article) shows a vortex at the edge of the L and one inside the diffuser, the video just mentions the vortex at the edge of the L." The picture shows two vortices, the huge one in the diffuser, and the small one at the edge of the L like in the video. Presumably the big vortex was beyond the scope of the video.
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Hmm, I'm not seeing the same as you. I see clear rotation on the inside of that fence, but high-velocity, non-rotating flow on the outside edge of the L:
