2 1 RESONANCE FOR MODULATED BOUNDARY-LAYER INSTABILITY WAVES - NEW EXPERIMENTAL RESULTS SHOWING QUADRATIC BREAKDOWN/

Boundary-layer instability waves are studied using the Orr-Sommerfield model. A spatial analysis has been performed using complex frequencie s to model modulated waves. The use of complex frequency has led to th e discovery of a pair of modes satisfying a 2:1 resonance condition. W ind-tunnel experiments have been carried out and show that the rapid n onlinear breakdown process is strongly enhanced for parameter values n ear the resonance condition. The breakdown is characterized by a quadr atic nonlinearity. The approach may have applicability to many nonline ar wave systems.