Low-dimensional manifolds in direct numerical simulations of premixed turbulent flames

2007 ◽  
Vol 31 (1) ◽  
pp. 1377-1384 ◽  
Author(s):  
J.A. van Oijen ◽  
R.J.M. Bastiaans ◽  
L.P.H. de Goey
Keyword(s):  
Numerical Simulations ◽  
Turbulent Flames ◽  
Direct Numerical Simulations ◽  
Premixed Turbulent Flames ◽  
Low Dimensional

scholarly journals Direct Numerical Simulations of the Impact of High Turbulence Intensities and Volume Viscosity on Premixed Methane Flames

2011 ◽  
Vol 2011 ◽  
pp. 1-12 ◽  
Author(s):  
Gordon Fru ◽  
Gábor Janiga ◽  
Dominique Thévenin
Keyword(s):  
Numerical Simulations ◽  
Heat Release ◽  
Turbulent Flame ◽  
Flame Structure ◽  
Turbulent Flames ◽  
Direct Numerical Simulations ◽  
Turbulent Reynolds Number ◽  
Volume Viscosity ◽  
Flame Structures ◽  
The Impact

Parametric direct numerical simulations (DNS) of turbulent premixed flames burning methane in the thin reaction zone regime have been performed relying on complex physicochemical models and taking into account volume viscosity (κ). The combined effect of increasing turbulence intensities (u′) andκon the resulting flame structure is investigated. The turbulent flame structure is marred with numerous perforations and edge flame structures appearing within the burnt gas mixture at various locations, shapes and sizes. Stepping upu′from 3 to 12 m/s leads to an increase in the scaled integrated heat release rate from 2 to 16. This illustrates the interest of combustion in a highly turbulent medium in order to obtain high volumetric heat release rates in compact burners. Flame thickening is observed to be predominant at high turbulent Reynolds number. Via ensemble averaging, it is shown that both laminar and turbulent flame structures are not modified byκ. These findings are in opposition to previous observations for flames burning hydrogen, where significant modifications induced byκwere found for both the local and global properties of turbulent flames. Therefore, to save computational resources, we suggest that the volume viscosity transport term be ignored for turbulent combustion DNS at low Mach numbers when burning hydrocarbon fuels.

Direct Numerical Simulations of turbulent flames to analyze flame/acoustic interactions

2009 ◽  
pp. 239-268 ◽  
Author(s):  
G. Fru ◽  
H. Shalaby ◽  
A. Laverdant ◽  
C. Zistl ◽  
G. Janiga ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Turbulent Flames ◽  
Direct Numerical Simulations

Low-dimensional models of a temporally evolving free shear layer

2009 ◽  
Vol 618 ◽  
pp. 113-134 ◽  
Author(s):  
MINGJUN WEI ◽  
CLARENCE W. ROWLEY
Keyword(s):  
Numerical Simulations ◽  
Shear Layer ◽  
Direct Numerical Simulations ◽  
Rate Of Change ◽  
Galerkin Projection ◽  
Free Shear Layer ◽  
Nonlinear Saturation ◽  
Complex Modes ◽  
Dimensional Models ◽  
Low Dimensional

We develop low-dimensional models for the evolution of a free shear layer in a periodic domain. The goal is to obtain models simple enough to be analysed using standard tools from dynamical systems theory, yet including enough of the physics to model nonlinear saturation and energy transfer between modes (e.g. pairing). In the present paper, two-dimensional direct numerical simulations of a spatially periodic, temporally developing shear layer are performed. Low-dimensional models for the dynamics are obtained using a modified version of proper orthogonal decomposition (POD)/Galerkin projection, in which the basis functions can scale in space as the shear layer spreads. Equations are obtained for the rate of change of the shear-layer thickness. A model with two complex modes can describe certain single-wavenumber features of the system, such as vortex roll-up, nonlinear saturation, and viscous damping. A model with four complex modes can describe interactions between two wavenumbers (vortex pairing) as well. At least two POD modes are required for each wavenumber in space to sufficiently describe the dynamics, though, for each wavenumber, more than 90% energy is captured by the first POD mode in the scaled space. The comparison of POD modes to stability eigenfunction modes seems to give a plausible explanation. We have also observed a relation between the phase difference of the first and second POD modes of the same wavenumber and the sudden turning point for shear-layer dynamics in both direct numerical simulations and model computations.

Bound-state formation in interfacial turbulence: direct numerical simulations and theory

2013 ◽  
Vol 716 ◽  
Author(s):  
M. Pradas ◽  
S. Kalliadasis ◽  
P.-K. Nguyen ◽  
V. Bontozoglou
Keyword(s):  
Numerical Simulations ◽  
State Formation ◽  
Stokes Equations ◽  
Bound State ◽  
Direct Numerical Simulations ◽  
Navier Stokes ◽  
Surface Boundary ◽  
Navier Stokes Equations ◽  
Oscillatory Dynamics ◽  
Low Dimensional

AbstractWe examine pulse interaction and bound-state formation in interfacial turbulence using the problem of a falling liquid film as a model system. We perform direct numerical simulations (DNSs) of the full Navier–Stokes equations and associated wall and free-surface boundary conditions and we examine both analytically and numerically a low-dimensional (LD) model for the film. For a two-pulse system, DNSs reveal the existence of very rich and complex pulse interactions, characterized by either overdamped, underdamped or self-sustained oscillating behaviours, all of them found to be in excellent agreement with LD results. Having demonstrated the reliability of the LD model for two-pulse systems/smaller domains, we use it to investigate larger domains with many interacting pulses, where DNSs are computationally expensive. We demonstrate that such systems are likely to be dominated by a self-sustained oscillatory dynamics.

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