Boundary-layer stability analysis of NLF and LFC experimental data at subsonic and transonic speeds

NASA-Lewis has conducted wind tunnel experiments to ascertain the effectiveness of state-of-the-art in natural laminar flow (NLF) and LFC airfoils for subsonic and transonic speeds, such as the NLF(1)-0414F and the SCLFC(1)-0513F. Attention is given to the effects of Tollmien-Schlichting (TS) and/or crossflow linear mechanisms amplifying small disturbances to generate turbulence. It is found that the incompressible TS transitional n-factors were generally in the 9-12 range, in agreement with earlier correlation studies; the TS instability was the dominant instability mode on a swept-planform LFC airfoil over the entire range of test conditions.