Predicted and hot-film measured Tollmien-Schlichting wave characteristics

The Tollmien-Schlichting (TS) instability is a time-dependence instability which can lead to transition of laminar boundary layers on airfoils. A comparison of theoretical predictions and experimental observations of the TS instability on the NLF(1)-0414F airfoil designed by Viken and Pfenninger. The theoretical predictions were obtained using the SALLY stability code. Test results, from the same hot films that were used to detect transition, revealed that TS waves could be detected by the hot films if the hot-film signal was adequately modified.