I found a very well done video which explains the two different sources of drag:- pressure (or form) drag, basically the "void" created by a wide wake that pulls back
- friction drag, the friction of the air or water alongside the whole cord of the foil

dimples make the flow "stick" longer with the object, closing the wake, reducing the pressure drag but increasing the friction drag

vortex generators on the leading edge have the opposite effect in reducing the friction drag but not trying to reduce the pressure drag

Dimples on a golf ball works because the gold ball shape is not streamlined and has a huge pressure drag but a small friction surface. But they do not work on fins, wings, foils because the pressure drag is so small to begin with.

Dimples on the leading edge can be useful on propellers because of the specific problem of cavitation

But on streamlined foils (airplane wings, wind turbine blades) what works is quobba-like "winglets" inducing vortexes in a way that does not adds lots of friction drag, unlike dimples.



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