On the excitation of Tollmien-Schlichting waves due to surface vibration

The effect of localised surface vibration on the stability of a Blasius boundary layer was studied. First it was demonstrated that small amplitude vibration of the order of less than 10µm can artificially excite Tollmien-Schlichting (TS) waves provided that the frequency of excitation was within the frequency band of the naturally occurring disturbance in the freestream environment. Longitudinally aligned motors generated more energetic TS wave and the growth rate increased with increasing number of live motors. But when a combination of both longitudinally and transversely align motors was tested a reduction in the growth rate was observed even when the total number of motors was larger than the most amplified case which was generated by 5 motors along the longitudinal axis