The transition process on crossflow-dominated swept wings undergoes three distinct stages: receptivity, disturbance growth, and breakdown. The details of the physical mechanisms active in each render the common industrial tool for transition prediction, the eNmethod, unable to produce acceptable results. An alternative method that accounts for the physical mechanisms of crossflow transition is required if better results are to be obtained. Experiments at the Arizona State University Unsteady Wind Tunnel have been performed to investigate each stage. Results from receptivity and breakdown experiments are presented here. The experiments show that the most important feature of the receptivity phase is mode selection and that selection of traveling- or stationary-wave-dominated transition depends on both turbulence intensity and surface roughness. The breakdown experiments elucidate the role of the high-frequency secondary instability as the breakdown mechanism and find that destabilization of the secondary instability is a useful transition criterion. The experimental results are used to suggest an alternative prediction method. 2001 by the authors.
