MALALASEKERA, W....et al., 2008. LES of recirculation and vortex breakdown in swirling flames. Combustion Science and Technology, 180(5), pp. 809-832.
In this study large eddy simulation (LES) technique has been applied to predict a selected
swirling flame from the Sydney swirl burner experiments. The selected flame is known as the
SM1 flame operated with fuel CH4 at a swirl number of 0.5. In the numerical method used,
the governing equations for continuity, momentum and mixture fraction are solved on a
structured Cartesian grid. Smagorinsky eddy viscosity model with the localised dynamic
procedure of Piomelli and Liu is used as the subgrid scale turbulence model. The conserved
scalar mixture fraction based thermo-chemical variables are described using the steady
laminar flamelet model. The GRI 2.11 is used as the chemical mechanism. The Favre filtered
scalars are obtained from the presumed beta probability density function (β -PDF) approach.
The results show that with appropriate inflow and outflow boundary conditions LES
successfully predicts the upstream recirculation zone generated by the bluff body and the
downstream vortex breakdown zone induced by swirl with a high level of accuracy. Detailed
comparison of LES results with experimental measurements show that the mean velocity field
and their rms fluctuations are predicted very well. The predictions for the mean mixture
fraction, subgrid variance and temperature are also reasonably successful at most axial
locations. The study demonstrates that LES together with the laminar flamelet model in
general provides a good technique for predicting the structure of turbulent swirling flames.