THESE de DOCTORAT - cerfacs

2
Computation of noise generated by combustion
Contents
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.2 Direct Computation of noise through Large Eddy Simulation . . . . . . . . . 23
2.2.1 Governing equations of turbulent reacting flows . . . . . . . . . . . . . . 23
2.2.2 Large Eddy Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.3 Hybrid computation of noise: Acoustic Analogies . . . . . . . . . . . . . . . . 26
2.3.1 An energy expression useful for acoustics . . . . . . . . . . . . . . . . . . 26
2.3.2 Lighthill’s Analogy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.3.3 Phillips’ Analogy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.3.4 Solving Lighthill’s analogy analytically . . . . . . . . . . . . . . . . . . . 37
2.1 Introduction
Studies on combustion noise carried out by Bragg in 1963, recognized that a flame behaves as
a monopole radiator [9], due to the isotropic volumetric expansions induced by the dilatation
of gases once combustion occurs. Further on, the same year, Smith & Khilam stated that a
turbulent flame could be seen as acoustically equivalent to a set of monopole sources, each of
them radiating at different strengths, frequencies and phases [95]. Thomas & Williams in 1966
[100] did perhaps the first significative experimental study concerning direct combustion noise.
20