Spatial hot-wire visualization of the Lambda-structure transformation into the turbulent spot on the smooth flat plate surface and riblet effect on this process

Artikel i vetenskaplig tidskrift, 2010

Evolution of the Lambda-vortex and its transformation into the turbulent spot in a flat plate boundary layer are investigated experimentally. Extensive measurements visualizing the Lambda-structure transformation into the turbulent spot on the smooth and ribbed surfaces of the flat plate are presented. The flow behavior in the course of spatial evolution of the Lambda-structure and turbulent spot is discussed. Specific features of the downstream evolution of Lambda-structure and turbulent spot on the smooth and ribbed surfaces are demonstrated, such as suppression by riblets of the Lambda-vortex transformation into the turbulent spot, appearance of the coherent structures of Lambda-vortex within ensemble-averaged turbulent spot, and oblique waves generation both by the Lambda-vortex and turbulent spot.