I admit to having been cursory in my reading, and now being confused. Aren't both the laminar and turbulent boundary layers lower limits - and the turbulent one being lower? I would expect the flow to be laminar or turbulent depending on weather (on water, this includes the waves) and the surrounding surface, and the laminar boundary layer as the lower limit.

On the other hand, larger-scale turbulence and differing wind speeds might be a limit on rotor diameter indepentently of height.

_{*Lunatic*, n.
One whose delusions are out of fashion.}