Boundary layer separation is generally undesirable in aircraft high lift coefficient systems and jet engine intakes.
[3] Thin membrane wings found on bats and insects have features which appear to cause favourable roughening at the Reynolds numbers involved, thereby enabling these creatures to fly better than would otherwise be the case.
Roughening causes the boundary layer to become turbulent and remain attached farther round the back before breaking away with a smaller wake than would otherwise be the case.
[5] In the case of a freestream flow past a cylinder, three methods may be employed to control the boundary layer separation that occurs due to the adverse pressure gradient.
Their low-drag wind tunnel results led to them being used on aircraft such as the P-51 and B-24 but maintaining laminar flow required low levels of surface roughness and waviness not routinely found in service.
[7] Krag[8] states that tests on the P-51 airfoil done in the high speed DVL wind tunnel in Berlin showed the laminar flow effect completely disappeared at real flight Reynolds numbers.
Implementing laminar flow in high-Reynolds-number applications generally requires very smooth, wave-free surfaces, which can be difficult to produce and maintain.
[13] In aeronautical engineering, boundary layer control may be used to reduce parasitic drag and increase usable angle of attack.