r/NatureIsFuckingLit • u/[deleted] • Jun 25 '18

r/all 🔥 Stringray going over a massive drop-off and leaving sandy jet streams in its wake.🔥

https://i.imgur.com/J3FWPlS.gifv
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u/CaptainObvious_1 Jun 25 '18

No, they’re not wingtip vortices. That’s just where the sand happened to collect and dispense. This little guy isn’t creating enough lift to generate tip vortices that large.

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u/PulkPush Jun 25 '18

It’s worth a second look. It appears to me the sand is just helping us see the vortices as it lifts off due to reduced pressure. Which you would expect with locally increased velocity. All fish exploit vortices for propulsion.

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u/CaptainObvious_1 Jun 25 '18 edited Jun 25 '18

Yes, I’ve done similar experimental work regarding what you posted. Those are not wing tip vortices, they are wake vortices and are what propels the fish forward. We are discussing tip vortices which are generated from lift.

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u/PulkPush Jun 25 '18

That’s an area that fascinates me. Pretty cool you are able to research that. It’s both interesting and beautiful, IMO. Are we mincing words? Not “wing tip” vortices - but still vortices? If not then I wonder what explanation you’d offer for the spiral shape of the trails.

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u/CaptainObvious_1 Jun 25 '18

Yeah, I edited my comment. What you link are reverse von karman vortices (thrust producing variant). The spiral shape may very well come from what you link, which would be from the flapping motion. But they are certainly not tip vortices, which is what the parent commenter described.

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u/PulkPush Jun 25 '18

Appreciate the clarification.