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AeroMcAeroFace · 12-16-2020, 11:48 AM

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)

"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.

"Finally, the article ends with the explanation that fences in the middle of diffusers are there specifically to generate vortices to improve generation of downforce, whereas the guy in the video says that the fences are there to separate wheel flow from the inward part of the diffuser and that this improves downforce by not messing up the flow, essentially (last two minutes of the video)." I don't know, I think it is a bit of both, tyre squirt probably affects a diffuser, and the generation of vortices stop the squirt being as much. The vortices (as mentioned in the article) improve downforce generation, probably partly due to a sealing effect and probably partly blocking air ingress from tyre squirt.

"Two different explanations, but I don't know which one is correct. Perhaps neither." I think they are both correct. But I think both are credible, if a bit simplified and too definite, it is probably something in the middle.

I am no expert and that article was a good read. Hopefully somebody who knows more than me can help.

12-16-2020, 11:48 AM	#11 (permalink)
AeroMcAeroFace Long time lurker Join Date: May 2019 Location: Uk Posts: 218 Thanks: 110 Thanked 153 Times in 119 Posts	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) "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. "Finally, the article ends with the explanation that fences in the middle of diffusers are there specifically to generate vortices to improve generation of downforce, whereas the guy in the video says that the fences are there to separate wheel flow from the inward part of the diffuser and that this improves downforce by not messing up the flow, essentially (last two minutes of the video)." I don't know, I think it is a bit of both, tyre squirt probably affects a diffuser, and the generation of vortices stop the squirt being as much. The vortices (as mentioned in the article) improve downforce generation, probably partly due to a sealing effect and probably partly blocking air ingress from tyre squirt. "Two different explanations, but I don't know which one is correct. Perhaps neither." I think they are both correct. But I think both are credible, if a bit simplified and too definite, it is probably something in the middle. I am no expert and that article was a good read. Hopefully somebody who knows more than me can help.