Simulation of vortex core precession in a reverse-flow cyclone

A large-eddy simulation of the single-phase turbulent flow in a model cyclone geometry on a uniform, cubic computational grid consisting of 4.9 x 10⁶ cells was performed. The Navier-Stokes equations were discretized according to a lattice-Boltzmann scheme. The Reynolds number, based on the inlet velocity and the cyclone body diameter, was 14,000. A standard Smagorinsky subgrid-scale model with c(s) = 0.1, including wall-damping functions, was applied. The 3-D, average flow field was predicted with a high level of accuracy. Furthermore, the simulations exhibit vortex-core precession, that is, the core of the main vortex is observed to move about the geometrical axis of the cyclone in a quasi-periodic manner. The Strouhal number associated with the simulated vortex-core precession was 0.53, whereas 0.49 was experimentally observed in a similar geometry at approximately the same Reynolds number.