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Optimal perturbations in boundary layer flows over rough surfaces

Article dans une revue avec comité de lecture
Author
CHERUBINI, Stefania
134975 Laboratoire de Dynamique des Fluides [DynFluid]
DE TULLIO, Marco
DE PALMA, Pietro
19097 Dipartimento di Ingegneria Meccanica e Gestionale [DIMEG]
PASCAZIO, Giuseppe

URI
http://hdl.handle.net/10985/9013
DOI
10.1115/1.4025028
Date
2013
Journal
Journal of Fluids Engineering

Abstract

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.

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