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An experimental investigation on waves and coherent structures in a three-dimensional open cavity flow
thesis
posted on 2017-02-17, 02:57 authored by Basley, Jeremy Clement DanielA space-time study of a three-dimensional nonlinearly saturated open
cavity flow is undertaken using time-resolved space-extended experimental data,
acquired in both cross-stream and spanwise planes, in incompressible air and water
flows. Through multiple modal decompositions in time and space, the waves and
coherent structures composing the dynamics in the permanent regime are identified
and characterised with respect to the instabilities arising in the flow.
Effects of nonlinearities are thoroughly investigated in the impinging shear layer,
regarding the self-sustained oscillations and their interactions with the inner-flow. In
particular, the analysis conducted throughout the parameter space enlightens a global
connection between the selection of locked-on modes and the amplitude modulation at
the impingement and the mode switching phenomenon. Furthermore, observations of
low frequencies interacting drastically with the shear layer flapping motion underline
the existence of intrinsic coherent three-dimensional dynamics inside the cavity in
spite of the shear layer disturbances.
Linear stability analyses have demonstrated the onset of centrifugal instabilities
along the main recirculation. In the present investigation, we focus on the dynamics
after saturation occurred. It reveals numerous space-time coherent structures, whose
properties are quantified and classified with respect to the underlying instabilities. We
observe travelling or standing spanwise waves, as well as steady structures. Finally,
some patterns exhibited by the saturated structures suggest that the nonlinear
mechanisms governing the mutations of the flow after the linear regime could gain
more insight in the frame of amplitude equations. Thesis submitted to obtain the joint degree of Doctor of Philosophy of Université Paris-Sud Département de Physique Ecole Doctorale MIPEGE and Monash University Department of Mechanical and Aerospace Engineering.
History
Campus location
AustraliaPrincipal supervisor
Julio SoriaAdditional supervisor 1
Luc PasturAdditional supervisor 2
François LusseyranYear of Award
2012Department, School or Centre
Mechanical and Aerospace EngineeringAdditional Institution or Organisation
Université Paris-Sud. Département de Physique. LIMSICourse
Doctor of PhilosophyDegree Type
DOCTORATEFaculty
Faculty of EngineeringUsage metrics
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No categories selectedKeywords
1959.1/893068Amplitude modulationOpen accessLocked-on modesKelvin-HelmholtzMode switchingthesis(doctorate)Space-time dynamicsOpen cavity2012Time-resolved PIVFourier transformethesis-20130307-025426Taylor-Görtlermonash:120075Three-dimensional flowsHilbert-Huang transformCentrifugal instabilitiesSpectral analysisTravelling wavesInterferencesImpinging shear layer
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