4. Experimental streak production

We explored the possibility of experimentally producing streaks close to their theoretically studied optimal counterparts, in order to assess their stabilizing effect on Tollmien-Schlichting waves. We chose to generate the vortices using roughness elements placed on the wall, a method that could be promising for possible industrial applications. An appropriate distribution (see figure 5 ) of these small cylindrical roughness elements placed on the wall in a boundary layer generates quasi-longitudinal vortices sufficiently far downstream, which...