Variable N-factor method for transition prediction in three-dimensional boundary layers

Linear amplitude methods are presented for estimating the location of trans ition caused by crossflow instabilities, intended for moderate- to low-turb ulence environments. A linear amplitude-based method combines receptivity, linear growth, and an amplitude correlation for predicting transition. Info rmation about the model surface finish (and/or suction distribution) and th e freestream disturbance environment is accounted for through the receptivi ty process. The variable N-factor method is presented as a limiting case, f ollowing simplifying assumptions about the receptivity. Transition N factor s are presented as a function of the surface roughness. Results show a very good correlation between the variable N-factor method and experimental dat a.