The non-reacting flow fields of the stratified swirl combustor with a central bluff-body were studied through large eddy simulation (LES) under three swirl numbers 0.25

0.45 and 0.79. Smagorinsky eddy viscosity model with dynamic procedure was selected as the sub-grid scale turbulence model. Influence of swirl intensity on the bluff-body recirculation zone

vortex breakdown and precessing motion was investigated. The LES results showed overall good agreement with experimental data. The axial lengths of bluff-body recirculation zone approximately 20mm showed no obvious variation under three swirl numbers. Q-criterion was used to visualize vortices structures

the spiral vortices were formed as the result of the Kelvin-Helmholtz instability of swirl shear layers; the vortex breakdown occurred upstream with the increase of swirl intensity. Power spectrum density (PSD) indicates the existence of precession motion

which decays along the flow direction. And precession motion appears at the terminal of bluff-body recirculation zone under higher swirl numbers 0.45 and 0.79. The precession frequencies are approximately 78Hz under three swirl numbers.