Riblet-assisted control of transformation of the Λ-structure into a turbulent spot Chernorai, V.G., Litvinenko, Yu.A., Kozlov, V.V., Loefdahl, L., Grek, G.R., Chun, H.H. 2005 Thermophysics and Aeromechanics 12 (4), 539–548, MAIK Nauka/Interperiodica Publishing 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.