Transition delay by means of a passive mechanism

Authors: Fransson, J. H. M., Talamelli, A., Brandt, L.B., Cossu, C.
Document Type: Conference
Pubstate: Published
Journal: 58th Meeting of the APS Division of Fluid Dynamics, Nov. 20-22, Chicago (IL), USA. Abstract in Bull. Am. Phys. Soc.
Volume: 50  
Year: 2005


Reducing the skin friction is important in nature and in many technological applications when larger speeds or lower energy consumptions are sought for. This reduction may be achieved by reducing stresses in turbulent boundary layers for instance tailoring biomimetic rough skins. Here we take a second approach consisting in keeping the boundary layer laminar as long as possible. We report the results of wind-tunnel experiments, motivated by previous theoretical analyses in which a well controlled spanwise periodic modulation of the boundary layer thickness is induced by using suitably designed roughness elements placed on the skin. We show, both with smoke visualization and measurements, that using this passive control technique it is possible to sensibly delay transition to turbulence.