The role of laminar separation bubble on low Reynolds number airfoils

Low Reynolds number airfoils are prone to be adversely affected by the presence of laminar separation bubbles (LSB). But at relatively high Reynolds number (based on the chord of the airfoil) of 100,000 and 200,000, suppression of LSB, by a boundary layer trip, caused the performance of the airfoil to deter further and the purpose of using a boundary layer trip seems to be defeated. With a boundary layer trip placed in the leading edge of E387 and FX63-137, LSB was suppressed and subsequent measurements show that the performance is affected drastically. The trip causes the turbulent boundary layer to separate early, at relatively high angles of attack, and augmenting the form drag.