Non-normality and nonlinearity in combustion–acoustic interaction in diffusion flames

Balasubramanian., Koushik ; Sujith, R. I. (2008) Non-normality and nonlinearity in combustion–acoustic interaction in diffusion flames Journal of Fluid Mechanics, 594 . pp. 29-57. ISSN 0022-1120

Full text not available from this repository.

Official URL:

Related URL:


The role of non-normality and nonlinearity in flame–acoustic interaction in a ducted diffusion flame is investigated in this paper. The infinite rate chemistry model is employed to study unsteady diffusion flames in a Burke–Schumann type geometry. It has been observed that even in this simplified case, the combustion response to perturbations of velocity is non-normal and nonlinear. This flame model is then coupled with a linear model of the duct acoustic field to study the temporal evolution of acoustic perturbations. The one-dimensional acoustic field is simulated in the time domain using the Galerkin technique, treating the fluctuating heat release from the combustion zone as a compact acoustic source. It is shown that the coupled combustion–acoustic system is non-normal and nonlinear. Further, calculations showed the occurrence of triggering; i.e. the thermoacoustic oscillations decay for some initial conditions whereas they grow for some other initial conditions. It is shown that triggering occurs because of the combined effect of non-normality and nonlinearity. For such a non-normal system, resonance or ‘pseudoresonance’ may occur at frequencies far from its natural frequencies. Non-normal systems can be studied using pseudospectra, as eigenvalues alone are not sufficient to predict the behaviour of the system. Further, both necessary and sufficient conditions for the stability of a thermoacoustic system are presented in this paper.

Item Type:Article
Source:Copyright of this article belongs to Cambridge University Press.
ID Code:110008
Deposited On:21 Dec 2017 11:03
Last Modified:21 Dec 2017 11:03

Repository Staff Only: item control page