Non-normality of thermoacoustic interactions: An experimental investigation

Sathesh Mariappan, R. I. Sujith, Peter J. Schmid

Research output: Chapter in Book/Report/Conference proceedingConference contribution

7 Scopus citations


An experimental investigation of the non-normal nature of thermoacoustic interactions in an electrically heated horizontal Rijke tube is performed. Since non-normality and the associated transient growth are linear phenomena, the experiments have to be confined to the linear regime. The bifurcation diagram for the subcritical Hopf bifurcation into a limit cycle behavior has been determined, after which the amplitude levels, for which the system acts linearly, have been identified for different power inputs to the heater. There are two main objectives for this experimental investigation. The first one deals with the extraction of the linear eigenmodes associated with the acoustic pressure from experimental data. This is accomplished by the Dynamic Mode Decomposition (DMD) technique applied in the linear regime. The non-orthogonality between the eigenmodes is determined for various values of heater power. The second objective is to identify evidence of transient perturbation growth in the system. The total acoustic energy in the duct has been monitored as the thermoacoustic system has been initialized by linear combinations of the two dominant eigenmodes. Transient growth, on the order of previous theoretical studies, has been found, and its parameter dependence on amplitude ratio and phase angle of the initial eigenmode components has been determined. This study represents the first experimental confirmation of non-normality in thermoacoustic systems. © 2011 by S. Mariappan, R. I. Sujith and P. J. Schmid.
Original languageEnglish (US)
Title of host publication47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit 2011
PublisherAmerican Institute of Aeronautics and Astronautics
ISBN (Print)9781600869495
StatePublished - Jan 1 2011
Externally publishedYes

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