ABSTRAKT

To investigate the impact of riblets aligned in the main flow direction on laminar-turbulent transition large-eddy simulations (LES) of spatially evolving flat plate zero-pressure gradient boundary layer are performed. By superimposed disturbances on the Blasius velocity profile at the inflow boundary natural K-type transition is triggered. A clean surface configuration and two riblet surface configurations are investigated. The two-dimensional Tollmien-Schlichting (TS) waves are found to be amplified by the riblets, whereas three-dimensional disturbances are damped. Secondary flow structures induced by the riblets are found. Overall, transition to turbulence is delayed by the riblets.