scholarly journals Diffusion-flame flickering as a hydrodynamic global mode

2016 ◽  
Vol 798 ◽  
pp. 997-1014 ◽  
Author(s):  
D. Moreno-Boza ◽  
W. Coenen ◽  
A. Sevilla ◽  
J. Carpio ◽  
A. L. Sánchez ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Global Stability ◽  
Diffusion Flames ◽  
Temporal Stability ◽  
Critical Conditions ◽  
Global Mode ◽  
Laminar Jet ◽  
Global Stability Analysis ◽  
Jet Diffusion Flames ◽  
Spatio Temporal

The present study employs a linear global stability analysis to investigate buoyancy-induced flickering of axisymmetric laminar jet diffusion flames as a hydrodynamic global mode. The instability-driving interactions of the buoyancy force with the density differences induced by the chemical heat release are described in the infinitely fast reaction limit for unity Lewis numbers of the reactants. The analysis determines the critical conditions at the onset of the linear global instability as well as the Strouhal number of the associated oscillations in terms of the governing parameters of the problem. Marginal instability boundaries are delineated in the Froude number/Reynolds number plane for different fuel jet dilutions. The results of the global stability analysis are compared with direct numerical simulations of time-dependent axisymmetric jet flames and also with results of a local spatio-temporal stability analysis.

scholarly journals Global stability analysis of lifted diffusion flames

2017 ◽  
Vol 126 ◽  
pp. 867-874 ◽  
Author(s):  
C. Mancini ◽  
M. Farano ◽  
P. De Palma ◽  
J.C. Robinet ◽  
S. Cherubini
Keyword(s):  
Stability Analysis ◽  
Global Stability ◽  
Diffusion Flames ◽  
Global Stability Analysis

Global Stability Analysis of an Academic Rotor/Stator Cavity Subject to Periodic and Simple Wall Oscillations

2021 ◽  
Author(s):  
Mark Noun ◽  
Laurent Gicquel ◽  
Gabriel Staffelbach
Keyword(s):  
Stability Analysis ◽  
Global Stability ◽  
Pressure Fluctuations ◽  
Dynamic Mode Decomposition ◽  
Forced Flow ◽  
Dynamic Mode ◽  
Global Stability Analysis ◽  
Eddy Simulation ◽  
Mode Decomposition ◽  
Spatio Temporal

Abstract Complex unsteady phenomena can appear in turbomachinery components and result in the self-sustained oscillatory motion of the fluid as found in aeronautical engines or rocket turbopumps for example. The origin of these oscillations often results from the complex coupling between flow non linearities and structure motion generating major risks for the operation of the engine and even undermining its components. For instance, in turbines, the internal components that are most liable to vibrate are the blades and discs. In this context, it is critical to understand the effect of the vibrating components on the flow stability in rotor/stator cavities. In order to address this problem, an academic rotor/stator cavity subject to periodic wall oscillations is investigated in the current paper where the frequency of the vibrations are imposed and correspond to the previously identified unstable fluid modes inside the cavity. The objective is to understand the behavior of the flow when subject to a periodic forcing imposed by the rotor motion. To do so, predictive numerical strategies are established based on Large Eddy Simulation (LES) in conjunction to a global stability analysis which seem to be a promising method to capture flow instabilities. Focus is here brought to the underlying pressure fluctuations found inside the cavity using spectral analysis complemented with the global stability analysis, demonstrating that such tools can address forced flow problems. More specifically and for all simulations, the results of the global stability analysis are compared to a Dynamic Mode Decomposition (DMD) of LES predictions by reconstructing the corresponding modes through a spatio-temporal approach showing that the new fluid limit cycles present modes that shift or completely disappear compared to the unforced case, the forcing mechanism altering the stability of the entire system.

A PIV investigation of weakly buoyant laminar jet diffusion flames

2000 ◽  
Author(s):  
Mark Wernet ◽  
Paul Greenberg ◽  
Peter Sunderland ◽  
William Yanis
Keyword(s):  
Diffusion Flames ◽  
Laminar Jet ◽  
Jet Diffusion Flames

scholarly journals Volterra–Lyapunov Stability Analysis of the Solutions of Babesiosis Disease Model

Symmetry ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1272
Author(s):  
Fengsheng Chien ◽  
Stanford Shateyi
Keyword(s):  
Mathematical Model ◽  
Stability Analysis ◽  
Global Stability ◽  
Numerical Simulations ◽  
Lyapunov Stability ◽  
Disease Model ◽  
Transmission Dynamics ◽  
Global Stability Analysis ◽  
Lyapunov Stability Analysis ◽  
Disease Free

This paper studies the global stability analysis of a mathematical model on Babesiosis transmission dynamics on bovines and ticks populations as proposed by Dang et al. First, the global stability analysis of disease-free equilibrium (DFE) is presented. Furthermore, using the properties of Volterra–Lyapunov matrices, we show that it is possible to prove the global stability of the endemic equilibrium. The property of symmetry in the structure of Volterra–Lyapunov matrices plays an important role in achieving this goal. Furthermore, numerical simulations are used to verify the result presented.

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