Simulation of the Stabilization Processes in Flames
Ecole Centrale de Lyon

Computational Modelling of
Turbulent Reacting Flows

and

Vortex Shedding past Bluff Bodies


Researchers: D. Lakehal, H. Lübcke, T. Rung
Sponsor: CNRS, DFG

                                                                                                                        		Technische Universität Berlin

 Fachgebiet: CFD

 Prof.Dr.-Ing. F.Thiele
A wide range of practical turbulent flows involve complex transient reactive processes which are still somewhat beyond comprehension to date. In such circumstances an accurate computational model can enhance the understanding of the principal mechanisms, in particular when turbulent effects become dominant (e.g. the mixing process in combustion chambers).

The degree of complexity increases in line with additional flow features, such as strong streamline curvature due to swirl, and it goes crescendo when the flow is governed by the interaction between distinct turbulence and combustion structures. Although a general approach would, arguably, be based on LES or even DNS, the present RANS approach is preferred for its robustness and reduced computational expenses. The practice is justifiable provided that it accurately returns the basic mechanisms related to turbulence.

Examples included refer to a non-reacting confined swirling flow (Fig. 1) and a turbulent reacting flow featuring a methane jet diffusion flame issuing into coflowing streams of air (Figs. 2,3,4). In the latter case, the combustion model employs a presumed beta-shape probability density function for the mixture fraction.

Fig.1: Confined swirling flow, 34k to load enlargement Fig. 1: Model combustion-chamber I (Johnson & Roback, 1983; ReDU=150 000)

Fig.2: Bluff-body burner, 9k to load enlargement Fig. 2: Model combustion-chamber II (Garreton et al.): Bluff-body stabilized
methane diffusion flame (geometry and streamlines)

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