Optimal perturbations in boundary layer flows over rough surfaces
Article dans une revue avec comité de lecture
Date
2013Journal
Journal of Fluids EngineeringRésumé
This work provides a three-dimensional energy optimization analysis, looking for perturbations inducing the largest energy growth at a finite time in a boundary-layer flow in the presence of roughness elements. The immersed boundary technique has been coupled with a Lagrangian optimization in a three-dimensional framework. Four roughness elements with different heights have been studied, inducing amplification mechanisms that bypass the asymptotical growth of Tollmien-Schlichting waves. The results show that even very small roughness elements, inducing only a weak deformation of the base flow, can strongly localize the optimal disturbance. Moreover, the highest value of the energy gain is obtained for a varicose perturbation. This result demonstrates the relevance of varicose instabilities for such a flow and shows a different behavior with respect to the secondary instability theory of boundary layer streaks.
Fichier(s) constituant cette publication
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- asme2e-ok.pdf
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- 3.173Mo
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- Description:
- JFE rough
- Fin d'embargo:
- 2017-11-08
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