Investigating mode competition and three-dimensional features from two-dimensional velocity fields in an open cavity flow by modal decompositions

Guéniat, Florimond and Pastur, Luc and Lusseyran, Francois (2014) Investigating mode competition and three-dimensional features from two-dimensional velocity fields in an open cavity flow by modal decompositions. Physics of Fluids, 26 (8). ISSN 1070-6631

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Official URL: https://aip.scitation.org/doi/10.1063/1.4891254

Abstract

Shear-layer driven open cavity ﬂows are known to exhibit strong self-sustained oscillations of the shear-layer. Over some range of the control parameters, a competition between two modes of oscillations of the shear layer can occur. We apply both Proper Orthogonal Decomposition and Dynamic Mode Decomposition to experimental two-dimensional two-components time and spaced velocity ﬁelds of an incompressible open cavity ﬂow, in a regime of mode competition. We show that, although proper orthogonal decomposition successes in identifying salient features of the ﬂow, it fails at identifying the spatial coherent structures associated with dominant frequencies of the shear-layer oscillations. On the contrary, we show that, as dynamic mode decomposition is devoted to identify spatial coherent structures associated with clearly deﬁned frequency channels, it is well suited for investigating coherentstructuresinintermittentregimes.Weconsiderthevelocitydivergenceﬁeld, inordertoidentifyspanwisecoherentfeaturesoftheﬂow.Finally,weshowthatboth coherent structures in the inner-ﬂow and in the shear-layer exhibit strong spanwise velocitygradients,andarethereforethree-dimensional

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This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Physics of Fluids (1994-present) 26, 085101 (2014); doi: 10.1063/1.4891254 and may be found at https://aip.scitation.org/doi/10.1063/1.4891254.

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https://doi.org/10.1063/1.4891254

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