Active control of Tollmien-Schlichting waves in the Blasius boundary layer by periodic wall suction

The appearance of turbulence downstream of a laminar flow section which has become unstable is considered, taking into account boundary-layer flows. It is pointed out that the instability begins with the growth of two-dimensional Tollmien-Schlichting waves. If the amplitude exceeds a certain threshold, the waves become unstable against three-dimensional disturbances. These developments lead to a fully developed turbulent flow. Aspects of transition control in the Blasius boundary layer are investigated. Attention is given to a description of the linear stability by the Orr-Sommerfeld eigenvalue problem, the employed numerical method, and the obtained numerical results. It is concluded that the wave induced by periodic wall suction/blowing has almost the same amplitude and phase distribution as a Tollmien-Schlichting wave.