What provides a higher lift to drag ratio, a thick laminar wing or a thinner wing with a vortex generator

Question

Recent readings have shown the benefits of "boundary layer tripping devices" or vortex generators for reducing drag and maintaining attached air flow at higher angles of attack.

It seems these generators effectively increase the width of the wing by creating an energized "fence", which further deflects the free air stream, almost acting as a lubricant to reduce friction drag on the surface of the wing and increasing the "bend" of the airstream, thereby increasing lift.

But generating these vortices comes at the expense of increased drag to create them, though they (and slats) could be made to be retractable.

Is there a clear advantage to either a thick laminar wing or a thinner one with vortex generators? The Reynolds number for the application would be around 200,000 to 500,000.

Answer 1

You confuse turbolators with vortex generators. And then you misunderstand the function of vortex generators.

Turbolators trip the boundary layer and change laminar to turbulent flow in order to enable the boundary layer to remain attached over a steep pressure rise. That is definitely required at the Reynolds numbers mentioned (200,000 to 500,000) in order to maximize performance.

Vortex generators work in a fully turbulent boundary layer and re-energize it by mixing more of the outer flow into it.

Both increase the boundary layer drag but help to prevent early separation. Only over the range of that prevented separation they reduce drag.

The answer to your question depends on the Reynolds number. At 1,000,000 and above, the laminar wing should be better and if you add boundary layer tripping at the right chord station, it also wins down to 200,000.