Riblet-assisted control of transformation of the Λ-structure into a turbulent spot

Artikel i vetenskaplig tidskrift, 2005

Experimental results are presented on transformation of a solitary Λ-structure into a turbulent spot and control of this process by means of riblets on the wetted surface in the boundary layer on a flat plate. It is shown that riblets exert a stabilizing effect on transformation of the Λ-structure into a turbulent spot. The Λ-structure on a smooth surface is shown to stretch in the streamwise direction and transform into a hairpin vortex, which becomes a turbulent spot further downstream. The intensity of the Λ-structure on riblets first increases and then decays further downstream, reaching less than half its value on a smooth surface. Finally, the Λ-structure decays on riblets without forming a turbulent spot.