Stability theory as a guide to the evaluation of transition data.

Dimensional analysis indicates that, in addition to the usual factors affecting transition, important additional parameters are a dimensionless frequency pv/U or wavelength U\/v and an orientation (0), which are characteristic of the initial disturbance spectrum. It is shown that the dependence on dimensionless wavelength can account for what has so far been regarded as a unit Reynolds number effect. Further, it is shown how these parameters can help in the orderly sorting out of transition results from different ground test facilities. The relation of these parameters to the predictability of transition in free flight is discussed.