THESE de DOCTORAT - cerfacs

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Abstract Today, much of the current effort in combustion noise is the development of efficient numerical tools to calculate the noise radiated by flames. Although unsteady CFD methods such as LES or DNS can directly provide the acoustic field radiated by noise sources, this evaluation is limited to small domains due to high computational costs. Hybrid methods have been developed to overcome this limitation. In these schemes, the noise sources are decoupled from the radiated sound. The sources are still calculated by DNS or LES solvers whereas the radiated sound is evaluated by acoustic tools using an acoustic analogy. In the present study, a numerical tool based on the Phillips analogy for low Mach number flows has been developed. This tool accounts for the role of the boundary conditions in the resulting acoustic field. Both LES and the acoustic solver developed here are used to assess the noise produced by a turbulent swirl-stabilized flame generated in a staged combustor. Good agreement is obtained between both techniques as long as the appropriate quantities are compared: the pressure signal obtained directly from LES contains a non negligible amount of hydrodynamic fluctuations that must be removed when a suitable comparison is sought with the acoustic solver. The low Mach number assumption is completely realistic when considering the flow within a combustion chamber; it also allows for considerable simplifications when dealing with acoustic analogies. However, it cannot be used for the upstream (air-intake, compressors) and downstream (turbines, nozzle) sections of an aeronautical combustion chamber. A numerical tool is developed based on the quasi-1D Linearized Euler Equations in order to account for convective, non-isentropic and non-isenthalpic flows. By means of this tool, it is possible to estimate the acoustic boundary conditions that should be imposed at the inlet/outlet of a given combustion chamber when performing low-Mach number acoustic computations. keywords: LES, combustion noise, acoustic analogies
Page 1: UNIVERSITE MONTPELLIER II SCIENCES
Page 5: An expert is a man who has made all
Page 8 and 9: Y gracias familia mía!!, que así
Page 13 and 14: Contents 1 General Introduction 13
Page 15 and 16: CONTENTS 5 6.4 Transmitted and refl
Page 17 and 18: LIST OF FIGURES 7 4.10 Analytical s
Page 19 and 20: LIST OF FIGURES 9 7.1 Air-intake du
Page 23 and 24: 1 General Introduction Contents 1.1
Page 25 and 26: 1.1 Noise in a combustion chamber 1
Page 27 and 28: 1.2 Scope of the present work 17 fl
Page 29 and 30: 1.3 Organization of the manuscript
Page 31 and 32: 2.1 Introduction 21 In their experi
Page 33 and 34: 2.2 Direct Computation of noise thr
Page 35 and 36: 2.2 Direct Computation of noise thr
Page 37 and 38: 2.3 Hybrid computation of noise: Ac
Page 51 and 52: 3 Development of a numerical tool f
Page 53 and 54: 3.1 Discretizing the Phillips’ eq
Page 55 and 56: 3.1 Discretizing the Phillips’ eq
Page 57 and 58: 3.3 Solving the system Ax = b 47 [
Page 59 and 60: 3.3 Solving the system Ax = b 49 wh
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3.3 Solving the system Ax = b 51 v
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3.3 Solving the system Ax = b 53
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3.4 GMRES 55 Stopping criteria of G
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3.4 GMRES 57 FGMRES x 0 m =1 AẐm
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4.1 Fundamental validation cases 59
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4.2 The 2D premixed laminar flame 6
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5.2 Experimental configuration 73 f
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5.3 Combustion noise Analysis 75 Mi
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5.3 Combustion noise Analysis 77
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5.3 Combustion noise Analysis 79 50
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5.3 Combustion noise Analysis 81 SP
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5.3 Combustion noise Analysis 83 Fi
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5.3 Combustion noise Analysis 85 Pr
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5.4 Filtering a LES pressure field
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5.4 Filtering a LES pressure field
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5.5 LES vs. Hybrid Results 91 400 H
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5.6 Conclusions 93 Ac. Energy (J)
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6 Boundary conditions for low Mach
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6.2 The quasi 1D Linearized Euler E
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6.3 The 1D linearized Euler equatio
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6.3 The 1D linearized Euler equatio
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6.4 Transmitted and reflected acous
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6.4 Transmitted and reflected acous
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6.5 When entropy does not remain co
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6.6 Transmitted and Reflected Waves
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7.2 Mean parameters of the Intake D
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7.3 Acoustic Evaluation 123 In the
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7.4 Helmholtz Solver Computation 12
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7.5 Conclusions 127 tion coefficien
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BIBLIOGRAPHY 129 [14] CHIU, H. H.,
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BIBLIOGRAPHY 131 [47] LEYKO, M., NI
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BIBLIOGRAPHY 133 [78] RAYLEIGH, L.
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A About the π c ′ = 0 assumption
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A.1 When is π T ′ equal to zero?
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B Publications In this appendix two
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141 Assessment of combustion noise
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143 d 2 π dt 2 − ∂ ( c 2 ∂π
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145 swirl motion in the D = 30 mm d
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147 wall. The ratio of the resolved
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149 50 x = 7 mm x = 17 mm 50 x = 27
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151 LES (AVBP) LES ASSUMPTION acous
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153 power is well captured by both
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155 [27] A. Lamraoui et al. “Acou
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157 required in addition to high-re
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159 flame/turbulence interactions a
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161 Observing with attention fig. ?
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163 SPL (dB) − micro 7 180 160 14
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