Experimental investigation on global instability and critical Reynolds number in roughness-induced laminar-to-turbulent transition

The present thesis provides an experimental confirmation of theoretically predicted flow instabilities downstream of a cylindrical roughness element in a laminar boundary layer. The experimental determination of the critical Reynolds number is of particular relevance for future applications of the threedimensional (3-D) global linear stability theory (LST). Moreover, the experiments demonstrate the significance of 3-D global LST in laminar-to-turbulent transition of a physical flow. The results of this work thus close the previous gap between theory and practical applications.