low Re we define as foils with Re < 150'000: case A: no microturbulence as in windtunnels. generally use flat profiles with a short section of negative pressure gradient at LE. tripping and separation avoidance devices are usually a must for Cl>0.5. e.g. Chang vortexgenerators at LE and oblique grooves following where pressure gradient is >0. case B: windtunnel applications. here use of such devices is a must, since microturbulence triggers separation of laminar B.L.