Experimental streak production
Delaying transition to turbulence

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...