Experiments on the stability of nonlinear waves in a boundary layer.
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This work investigated the interaction of two Tollmien-Schlichting waves in a Blasius boundary layer when the waves displayed weakly nonlinear behaviour. Two separate oscillating signals were introduced into a single vibrating ribbon, while the initial amplitudes of the disturbances were controlled. The subsequent growth, interaction, and break down of the two waves at different initial amplitudes were monitored using a fast Fourier-transform spectrum analyzer. The second harmonic component was observed to grow at twice the growth rate of the fundamental in a Reynolds number range where linear theory predicted attenuation. More-over, it was found that in addition to the difference frequency component, the 2FSUP1 - FSUP2 component also dominated the nonlinear growth regime leading to transition. These results are compared with the theoretical model of Nayfeh and Bozatli . (A)