Blar i NTNU Open på forfatter "Mensah, Georg"
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Degenerate perturbation theory in thermoacoustics: high-order sensitivities and exceptional points
Orchini, Alessandro; Magri, Luca; Silva, Camilo F.; Mensah, Georg; Moeck, Jonas (Peer reviewed; Journal article, 2020)In this study, we connect concepts that have been recently developed in thermoacoustics, specifically (i) high-order spectral perturbation theory, (ii) symmetry-induced degenerate thermoacoustic modes, (iii) intrinsic ... -
Intrinsic thermoacoustic modes in an annular combustion chamber
Buschmann, Philip Erik; Mensah, Georg; Moeck, Jonas (Peer reviewed; Journal article, 2020)Thermoacoustic instabilities originate from the interaction of unsteady heat release rate associated with flames and the acoustic modes of a combustor. A feedback loop not involving the natural acoustic modes has been ... -
Perturbation theory of nonlinear, non-self-adjoint eigenvalue problems: Semisimple eigenvalues
Orchini, Alessandro; Mensah, Georg; Moeck, Jonas (Peer reviewed; Journal article, 2021)We discuss high-order adjoint based degenerate perturbation theory of semisimple eigenvalues resulting from nonlinear eigenvalue problems, which are typical of acoustic problems and vibrational analysis. The theory is ... -
Perturbation theory of nonlinear, non-self-adjoint eigenvalue problems: Simple eigenvalues
Mensah, Georg; Orchini, Alessandro; Moeck, Jonas (Peer reviewed; Journal article, 2020)The study of the vibrational modes and stability of a given physical system is strongly tied to the efficient numerical evaluation of its eigenvalues. The operators governing the eigenproblem are, in general, nonlinear in ... -
Solution of Thermoacoustic Eigenvalue Problems with a Non-iterative Method
Buschmann, Philip Erik; Mensah, Georg; Nicoud, Franck; Moeck, Jonas (Peer reviewed; Journal article, 2020)Gas turbine combustors are prone to undesirable combustion dynamics in the form of thermoacoustic oscillations. Analysis of the stability of thermoacoustic systems in the frequency domain leads to nonlinear eigenvalue ... -
Thermoacoustic modes of intrinsic and acoustic origin and their interplay with exceptional points
Orchini, Alessandro; Silva, Camilo; Mensah, Georg; Moeck, Jonas (Peer reviewed; Journal article, 2020)We propose a general classification of all the modes of a given thermoacoustic system into two sets: one of acoustic origin and one of intrinsic thermoacoustic (ITA) origin. To do this, the definition of intrinsic modes, ...