Delaying Transition to Turbulence by a Passive Mechanism

by: Jens HM Fransson, Alessandro Talamelli, Luca Brandt, Carlo Cossu

Physical Review Letters, Vol. 96, No. 6. (2006)

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Abstract

Reducing skin friction is important in nature and in many technological applications. 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 of keeping the boundary layer laminar as long as possible by forcing small optimal perturbations. Because of the highly non-normal nature of the underlying linearized operator, these perturbations are highly amplified and able to modify the mean velocity profiles at leading order. We report results of wind-tunnel experiments in which we implement this concept by using suitably designed roughness elements placed on the skin to enforce nearly optimal perturbations. We show that by using this passive control technique it is possible to sensibly delay transition to turbulence.

@article{citeulike:2758380, abstract = {Reducing skin friction is important in nature and in many technological applications. 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 of keeping the boundary layer laminar as long as possible by forcing small optimal perturbations. Because of the highly non-normal nature of the underlying linearized operator, these perturbations are highly amplified and able to modify the mean velocity profiles at leading order. We report results of wind-tunnel experiments in which we implement this concept by using suitably designed roughness elements placed on the skin to enforce nearly optimal perturbations. We show that by using this passive control technique it is possible to sensibly delay transition to turbulence.}, author = {Fransson, Jens H. M. and Talamelli, Alessandro and Brandt, Luca and Cossu, Carlo }, citeulike-article-id = {2758380}, doi = {10.1103/PhysRevLett.96.064501}, journal = {Physical Review Letters}, keywords = {2006, cool, flow, focus, friction}, number = {6}, posted-at = {2008-05-05 17:30:43}, priority = {2}, publisher = {APS}, title = {Delaying Transition to Turbulence by a Passive Mechanism}, url = {http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal\&id=PRLTAO000096000006064501000001\&idtype=cvips\&gifs=yes}, volume = {96}, year = {2006} }

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TY - JOUR ID - citeulike:2758380 TI - Delaying Transition to Turbulence by a Passive Mechanism JF - Physical Review Letters VL - 96 IS - 6 PB - APS N2 - Reducing skin friction is important in nature and in many technological applications. 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 of keeping the boundary layer laminar as long as possible by forcing small optimal perturbations. Because of the highly non-normal nature of the underlying linearized operator, these perturbations are highly amplified and able to modify the mean velocity profiles at leading order. We report results of wind-tunnel experiments in which we implement this concept by using suitably designed roughness elements placed on the skin to enforce nearly optimal perturbations. We show that by using this passive control technique it is possible to sensibly delay transition to turbulence. KW - 2006 KW - cool KW - flow KW - focus KW - friction AU - Fransson, Jens AU - Talamelli, Alessandro AU - Brandt, Luca AU - Cossu, Carlo PY - 2006/// UR - http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRLTAO000096000006064501000001&idtype=cvips&gifs=yes ER -

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