Modeling variable density effects in turbulent flames—Some basic considerations

Chomiak, Jerzy; Nisbet, Jonny

doi:10.1016/0010-2180(95)00001-m

Cited by 55 publications

(38 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Flame generated turbulence was first indicated by Karlovitz et al [4] and was subsequently linked with the mean velocity gradient due to flame normal acceleration by Bray and Libby [12], with experimental confirmation by Moreau and Boutier [13]. Moreover, the preferential acceleration of low-density burned products in comparison to the higherdensity unburned reactants in response to the self-induced pressure gradient within the flame brush significantly affects the contribution of the mean pressure gradient to the turbulent kinetic energy transport [14][15][16]. The importance of the effect of the fluctuating pressure gradient on turbulent kinetic energy transport has been indicated by Kuznetsov [17] and Strahle [18], and was subsequently confirmed by DNS data analysis [19][20][21].…”

Section: Introductionmentioning

confidence: 96%

Statistics and Modelling of Turbulent Kinetic Energy Transport in Different Regimes of Premixed Combustion

Chakraborty

Katragadda

Cant

2010

Flow Turbulence Combust

View full text Add to dashboard Cite

The statistical behaviour of turbulent kinetic energy transport in turbulent premixed flames is analysed using data from three-dimensional Direct Numerical Simulation (DNS) of freely propagating turbulent premixed flames under decaying turbulence. For flames within the corrugated flamelets regime, it is observed that turbulent kinetic energy is generated within the flame brush. By contrast, for flames within the thin reaction zones regime it has been found that the turbulent kinetic energy decays monotonically through the flame brush. Similar trends are observed also for the dissipation rate of turbulent kinetic energy. Within the corrugated flamelets regime, it is demonstrated that the effects of the mean pressure gradient and pressure dilatation within the flame are sufficient to overcome the effects of viscous dissipation and are responsible for the observed augmentation of turbulent kinetic energy in the flame brush. In the thin reaction zones regime, the effects of the mean pressure gradient and pressure dilatation terms are relatively much weaker than those of viscous dissipation, resulting in a monotonic decay of turbulent kinetic energy across the flame brush. The modelling of the various unclosed terms of the turbulent kinetic energy transport equation has been analysed in detail. The predictions of existing models are compared with corresponding quantities extracted from DNS data. Based on this a-priori DNS assessment, either appropriate 206 Flow Turbulence Combust (2011) 87:205-235 models are identified or new models are proposed where necessary. It is shown that the turbulent flux of turbulent kinetic energy exhibits counter-gradient (gradient) transport wherever the turbulent scalar flux is counter-gradient (gradient) in nature. A new model has been proposed for the turbulent flux of turbulent kinetic energy, and is found to capture the qualitative and quantitative behaviour obtained from DNS data for both the corrugated flamelets and thin reaction zones regimes without the need to adjust any of the model constants.

show abstract

Section: Introductionmentioning

confidence: 96%

Statistics and Modelling of Turbulent Kinetic Energy Transport in Different Regimes of Premixed Combustion

Chakraborty

Katragadda

Cant

2010

Flow Turbulence Combust

View full text Add to dashboard Cite

show abstract

“…Another promising model has been proposed by Chomiak and Nisbet [10]. Their model assumes that both scalar transport and turbulence generation arising from pressure-density interactions in flames are attributable to the motion of large-scale turbulent thermals superimposed on the shear turbulence mechanism.…”

Section: Historical Perspectivementioning

confidence: 99%

“…For example, Chomiak and Nisbet [10] relied upon similarities to flows involving bubble dynamics in developing key parts of their formulation. The starting assumption for the current study is that buoyancy results in turbulent kinetic energy production through gravitational (hydrostatic) and baroclinic (hydrodynamic) vorticity generation (c.f., Tieszen, et al [11]).…”

Section: Present Workmentioning

confidence: 99%

See 1 more Smart Citation

A turbulence model for buoyant flows based on vorticity generation.

Domino¹,

Nicolette²,

O’Hern³

et al. 2005

View full text Add to dashboard Cite

A turbulence model for buoyant flows has been developed in the context of a k-ε turbulence modeling approach. A production term is added to the turbulent kinetic energy equation based on dimensional reasoning using an appropriate time scale for buoyancy-induced turbulence taken from the vorticity conservation equation. The resulting turbulence model is calibrated against far field helium-air spread rate data, and validated with near source, strongly buoyant helium plume data sets. This model is more numerically stable and gives better predictions over a much broader range of mesh densities than the standard k-ε model for these strongly buoyant flows.4

show abstract

“…When other processes are involved or when the unsteadiness of the flow is of importance LES is necessary to avoid excessive and complicated tailor-made modeling of the intrinsic coupling processes, [15], usually resulting in rather poor predictions, e.g. [16], usually with high case sensitivity. In the light of the above discussion, the aim of this study is to discuss the use of LES and Implicit LES (ILES), [17,18], for engineering flow problems, including geometrical complexity and physical complexity in terms of additional physics, i.e.…”

Section: Introductionmentioning

confidence: 99%