期刊
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
卷 27, 期 6, 页码 684-706出版社
ELSEVIER
DOI: 10.1016/j.euromechflu.2008.01.007
关键词
Roughness; Laminar boundary layer; Direct Numerical Simulation; Biglobal linear stability
The stability of the laminar boundary layer developing on a flat plate in the presence of a periodic row of roughness elements is investigated. A Direct Numerical Simulation is performed to compute the steady flow downstream of the roughness elements, which contains a pair of two counter-rotating streamwise vortices per element, which can be considered as a pre-streaky structure. The linear stability of this base flow is analyzed by means of the so-called biglobal stability approach. Three-dimensional eigenmodes are found, which are shown to be the continuation of the Tollmien-Schlichting waves present in the case of an unperturbed boundary layer. Moreover, a stabilizing effect due to the roughness-induced vortices is found. A Direct Numerical Simulation of the interaction between a two-dimensional Tollmien-Schlichting wave and the roughness array is also performed. The computed perturbation traveling downstream of the roughness elements is shown to be a linear combination of the biglobal eigenmodes. (C) 2008 Elsevier Masson SAS. All rights reserved.
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