Experimental transition and boundary-layer stability analysis for a slotted swept laminar flow control airfoil

One of the most important parameters to be determined during performance verification of low-drag airfoils is the location of boundary-layer transition. Equally important, however, is understanding the mechanisms which cause transition on a swept wing. Transition can be due to many instability mechanisms, including Tollmien Schlichting instability (TS), crossflow instability (CF), attachment line contamination (AL), and Gortler vortices (GV). For unswept wings, TS disturbance waves are the dominant cause of transition and adverse pressure distributions and increasing Reynolds number have a major influence in their growth. Experiments on swept wings [495, 502, 517] have shown that transition may occur near the leading edge due to the instability of crossflow velocity profiles in the boundary layer and stability theory shows that this instability can lead to transition [521, 529–532]. The major parameters that influence crossflow instability are wing sweep, pressure distribution, and Reynolds numbers.