Characterizing surface-gap effects on boundary-layer transition dominated by Tollmien–Schlichting instability

Effects of gaps (rectangular surface cavities) on boundary-layer transition are investigated using a combination linear stability theory and experiments, for boundary layers where the smooth-surface results from Tollmien–Schlichting (TS) instability. Results presented wide range gap characteristics, with associated locations ranging location all way forward to location. The movement is well described by variable $N$ -factor, which links characteristics level instability amplification $e^N$ leading transition. effects TS-wave characterized two limiting behaviours. For shallow $d/w < 0.017$ , reduction in -factor function depth $d$ independent width $w$ . deep > 0.028$ depth. When both sufficiently large relative displacement thickness $\delta ^*$ bypassed, resulting at These behaviours mapped out terms ( $w/ \delta $d/ ), providing predictive model