Nonlinear identification of unsteady heat transfer of a cylinder in pulsating cross flow

Selimefendigil, Fatih; Föller, S.; Polifke, Wolfgang

doi:10.1016/j.compfluid.2011.08.012

Cited by 35 publications

(18 citation statements)

References 36 publications

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“…To simulate the dynamics of the heater, Selimefendigil, Föller & Polifke (2008) have analysed the unsteady convective heat transfer from a heated circular cylinder. Following this approach, the above system of equations (4.6) is solved for the unsteady convective heat transfer over the circular cylindrical heated wire filament.…”

Section: Equations Governing the Hydrodynamic Zonementioning

confidence: 99%

Modelling nonlinear thermoacoustic instability in an electrically heated Rijke tube

Mariappan

Sujith

2011

J. Fluid Mech.

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An analysis of thermoacoustic instability is performed for a horizontal Rijke tube with an electrical resistance heater as the heat source. The governing equations for this fluid flow become stiff and are difficult to solve by the computational fluid dynamics (CFD) technique, as the Mach number of the steady flow and the thickness of the heat source (compared to the acoustic wavelength) are small. Therefore, an asymptotic analysis is performed in the limit of small Mach number and compact heat source to eliminate the above stiffness problem. The unknown variables are expanded in powers of Mach number. Two systems of governing equations are obtained: one for the acoustic field and the other for the unsteady flow field in the hydrodynamic zone around the heater. In this analysis, the coupling between the acoustic field and the unsteady heat release rate from the heater appears from the asymptotic analysis. Furthermore, a non-trivial additional term, referred to as the global-acceleration term, appears in the momentum equation of the hydrodynamic zone, which has serious consequences for the stability of the system. This term can be interpreted as a pressure gradient applied from the acoustic onto the hydrodynamic zone. The asymptotic stability of the system with the variation of system parameters is presented using the bifurcation diagram. Numerical simulations are performed using the Galerkin technique for the acoustic zone and CFD techniques for the hydrodynamic zone. The results confirm the importance of the global-acceleration term. Bifurcation diagrams obtained from the simulations with and without the above term are different. Acoustic streaming is shown to occur during the limit cycle and its effect on the unsteady heat release rate is discussed.

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Section: Equations Governing the Hydrodynamic Zonementioning

confidence: 99%

Modelling nonlinear thermoacoustic instability in an electrically heated Rijke tube

Mariappan

Sujith

2011

J. Fluid Mech.

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“…[1]). However, while there has been some recent work on the identification of nonlinear heat release models in time domain [40,41], this subject is considerably less advanced, and no general methodology exists to date which allows to set-up a nonlinear time-domain model for a practical flame valid for a range of amplitudes and frequencies and, in particular, combinations thereof. Such a model would be required for a time-domain bifurcation analysis of a thermoacoustic system with multiple unstable modes.…”

Section: Figurementioning

confidence: 99%

Nonlinear Interactions of Multiple Linearly Unstable Thermoacoustic Modes

Moeck

Paschereit

2012

International Journal of Spray and Combustion Dynamics

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We investigate the dynamics of thermoacoustic systems with multiple linearly unstable modes. If a linear analysis reveals more than one mode with positive growth rate, nonlinear methods have to be used to determine the existence and stability of steady-state oscillations. One possible way to engage this problem is a first-order harmonic balance approach based on describing function representations for the flame response. In contrast to the case of a single unstable mode, the nonlinearity output to multiple sinusoidal components with different frequencies and amplitudes has to be known. Based on this approach, we present conditions for the existence and stability of single-or multi-mode steady-state oscillations. We apply this method to a thermoacoustic model system having two linearly unstable modes. By varying one of the system parameters, we find stable and unstable single-mode steady-states as well as unstable simultaneous oscillations. Associated with the stability of the single-mode limit cycles, we identify hysteresis in the oscillation type. Some related experimental observations are discussed.

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“…These plots show the complicated interaction between the forced convection and natural convection. These plots are also important when one tries to get a mathematical model for the input (velocity forcing at the inlet) -output (Nusselt number at the bottom wall of the cavity) from the system identification [19].…”

Section: Resultsmentioning

confidence: 99%

Numerical analysis of mixed convection in pulsating flow for a horizontal channel with a cavity heated from below

Selimefendigil

2016

THERM SCI

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In this study, a channel with a cavity heated from below is numerically investigated for the mixed convection case in pulsating flow for a range of Richardson numbers (Ri = 0.1,1,10, 100) at Reynolds number of 50 in the laminar flow regime. At the inlet of the channel, pulsating velocity is imposed for Strouhal numbers between 0.1 to 1 and velocity amplitude ratio between 0.3 to 0.9. The effect of the pulsation frequency, amplitude, and Richardson number on the heat transfer enhancement is numerically analyzed. The results are presented in terms of streamlines, isotherm plots, and averaged Nusselt number plots. The fast Fourier transform plots for the Nusselt number response to single sinusoidal velocity forcing at the inlet and non-linearity in the response is also provided..

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Nonlinear identification of unsteady heat transfer of a cylinder in pulsating cross flow

Cited by 35 publications

References 36 publications

Modelling nonlinear thermoacoustic instability in an electrically heated Rijke tube

Modelling nonlinear thermoacoustic instability in an electrically heated Rijke tube

Nonlinear Interactions of Multiple Linearly Unstable Thermoacoustic Modes

Numerical analysis of mixed convection in pulsating flow for a horizontal channel with a cavity heated from below

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