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Thermoacoustic instability - a dynamical system and time domain analysis

Abstract : This study focuses on the Rijke tube problem, which includes features relevant to the modeling of thermoacoustic coupling in reactive flows: a compact acoustic source, an empirical model for the heat source, and nonlinearities. This system features both linear and nonlinear flow regimes with complex dynamical behavior. In order to synthesize accurate time-series, we tackle this problem from a numerical point-of-view, and start by proposing a dedicated solver designed for dealing with the underlying stiffness, in particular, the retarded time and the discontinuity at the location of the heat source. Stability analysis is performed on the limit of the low amplitude perturbations by means of the projection method proposed by Jarlebring (2008), which alleviates the linearization of the retarded term. The results are then compared to the analytical solution of the undamped system, in addition to the analysis based on Galerkin projection. The method provides insight into the consequence of the simplification due to assumption of continuous basis functions in the Galerkin expansion. We illustrate that due to the presence of a discontinuity in the spatial domain, the resulting Gibbs phenomenon together with frequency dependent damping causes the eigenvalues of the Galerkin expansion to be excessively damped. Finally, time-series in the fully nonlinear regime, where a limit cycle is established, are analyzed and modes are extracted using Dynamic Mode Decomposition. By comparing the modes of the linear to that of the nonlinear regime, we are able to illustrate the mean-flow modulation and frequency switching, which appear as the nonlinearities become significant and ultimately affect the form of the limit cycle. In conclusion, a dedicated solver for capturing thermoacoustic instability is proposed and methods for analyzing linear and nonlinear region of the resulting time-series are introduced.
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https://hal.archives-ouvertes.fr/hal-00918174
Contributor : Vincent Le Chenadec Connect in order to contact the contributor
Submitted on : Friday, December 13, 2013 - 8:48:21 AM
Last modification on : Wednesday, November 18, 2020 - 9:04:02 PM

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Taraneh Sayadi, Vincent Le Chenadec, Peter Schmid, Franck Richecoeur, Marc Massot. Thermoacoustic instability - a dynamical system and time domain analysis. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2014, 753, pp.448-471. ⟨10.1017/jfm.2014.357⟩. ⟨hal-00918174⟩

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