Sensitivity analysis of optimal transient growth for turbulent boundary layers
Résumé
Structural approaches based on modal decomposition of the flow dynamics have gained acceptance for
a wide variety of turbulent shear flows. In this context, a singular value decomposition associated with a
governing operator, aiming to model the linear amplification of coherent structures, is used to reproduce
some fundamental motions in a turbulent boundary layer. In particular, as already found by Cossu et al.
(2009), elongated streaky structures scaled in inner and outer units are identified. The sensitivity of these
singular values to a mean flow modification is analysed. It is illustrated that the linear amplification of very
large-scales which populate the outer motion is not affected when the leading singular value associated
with the inner layer is damped. Moreover, we notice that the resulting optimal mean flow deviation is
consistent with findings of Xu et al. (2007) in which the active control of a turbulent boundary layer is
studied through direct numerical simulations.
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