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dc.contributor.authorHemchandra, Santoshen_US
dc.date.accessioned2009-08-26T17:31:05Z
dc.date.available2009-08-26T17:31:05Z
dc.date.issued2009-05-13en_US
dc.identifier.urihttp://hdl.handle.net/1853/29615
dc.description.abstractThis thesis describes computational and theoretical studies of fundamental physical processes that influence the heat-release response of turbulent premixed flames to acoustic forcing. Attached turbulent flames, as found in many practical devices, have a non-zero mean velocity component tangential to the turbulent flame brush. Hence, flame surface wrinkles generated at a given location travel along the flame sheet while being continuously modified by local flow velocity disturbances, thereby, causing the flame sheet to respond in a non-local manner to upstream turbulence fluctuations. The correlation length and time scales of these flame sheet motions are significantly different from those of the upstream turbulence fluctuations. These correlation lengths and times increase with turbulence intensity, due to the influence of kinematic restoration. This non-local nature of flame sheet wrinkling (called 'non-locality') results in a spatially varying distribution of local consumption speed (i.e. local mass burning rate) even when the upstream flow statistics are isotropic and stationary. Non-locality and kinematic restoration result in coupling between the responses of the flame surface to coherent acoustic forcing and random turbulent fluctuations respectively, thereby, causing the coherent ensemble averaged component of the global heat-release fluctuation to be different in magnitude and phase from its nominal (laminar) value even in the limit of small coherent forcing amplitudes (i.e. linear forcing limit). An expression for this correction, derived from an asymptotic analysis to leading order in turbulence intensity, shows that its magnitude decreases with increasing forcing frequency because kinematic restoration limits flame surface wrinkling amplitudes. Predictions of ensemble averaged heat release response from a different, generalized modeling approach using local consumption and displacement speed distributions from unforced analysis shows good agreement with the exact asymptotic result at low frequencies.en_US
dc.publisherGeorgia Institute of Technologyen_US
dc.subjectHeat release responseen_US
dc.subjectTurbulent flamesen_US
dc.subjectLevel-seten_US
dc.subjectNon-localityen_US
dc.subjectTurbulent flame speeden_US
dc.subjectTransfer functionen_US
dc.subjectConsumption speeden_US
dc.subject.lcshTurbulence
dc.subject.lcshCombustion
dc.subject.lcshKinematics
dc.titleDynamics of turbulent premixed flames in acoustic fieldsen_US
dc.typeDissertationen_US
dc.description.degreePh.D.en_US
dc.contributor.departmentAerospace Engineeringen_US
dc.description.advisorCommittee Chair: Lieuwen, Tim; Committee Member: Menon, Suresh; Committee Member: Peters, Norbert; Committee Member: Yang, Vigor; Committee Member: Zinn, Benjaminen_US


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