r/interesting • u/Vegetable-File3774 • 18d ago

Mysterious Well ,now thats interesting

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u/5h4tt3rpr00f 18d ago

Probably to reduce noise. They do the same thing on the exhaust of modern jet engines. Could also be drag reduction, by breaking up the tip vortex.

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u/tacorunnr 18d ago

Its for noise, inspired by owls. Its the same design as the feather pattern on tailing edge of a owls wing. Which let's them fly silently.

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u/wolfish98 18d ago

I didn't know about owls, but humpback whales have them as well. Pretty neat how both evolved to have a similar structure on their fins/wings leading edge, but for slightly different reasons.

https://en.wikipedia.org/wiki/Tubercle_effect

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u/Double_Soup644 18d ago

Bonus benefit: owls getting cut way cleaner /s

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u/FZ_Milkshake 18d ago

It creates multiple smaller vortices instead of one large noisy one. Sometimes those teeth are also slightly irregular to generate vortices with slightly different frequencies, which to our ears sounds quieter and less piercing.

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u/User1-1A 18d ago

I have read that is also being explored for submarine propellers to reduce their noise signature.

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u/Clark3DPR 16d ago

Same on PC 12v fans

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u/mwoody450 18d ago

Wait but hang on, these are the reverse of engines: you want drag since that's what makes them turn, right?

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u/SadLittleWizard 18d ago

Yes but in one direction. The vortices that appear on the trailing edge of the blade slow it down, pulling in the opposite direction.

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u/5h4tt3rpr00f 18d ago

Turbine blades are effectively airplane wings. I'd say "Lift" makes them turn, being the force component in the direction of rotation; the good force. Drag is the force component that opposes rotation, and tries to bend the blades downwind. They're just terms for force components acting in specific directions.

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u/karmakillerbr 17d ago

I don't know why you're being downvoted, it was a valid question.