The effect of dimpling is dependent on Reynold's Number (Re) and can precipitate an earlier transition from laminar to turbulent flow. Similar situation results in golf balls being dimpled ...
Not a great deal of use with an aircraft due to the larger areas and boundary layer thickness, not to mention the manufacturing and potential handling problems if dimpling were to be used, say, on wing surfaces due to in-service deterioration and asymmetric separation patterns.
Perhaps the currently practising aerodynamicists can offer more up to date comment ?
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