Turbulent flow structure and swirl number effect in a cyclone

The turbulent flow within a cylinder-on-cone cyclone is highly three-dimensional and our knowledge of this flow has yet to be improved. This work aims to improve our understanding of the flow structure, with special attention to the swirl number effect. The three velocity components of the flow were measured using LDA and PIV. The Reynolds number, based on the inlet velocity and the cyclone cylindrical chamber diameter, was 7.4 104, and the swirl number examined was from 2.4 to 5.3. Three regions of the flow have been identified after careful analysis of the data, which are referred to as the core, the outer and the wall-affected regions, respectively; each is distinct from another in terms of the vorticity concentration, frequency of quasi-periodical coherent structure, the probability density function, and mean and variance of velocities. It has been found that the flow, including its Strouhal numbers and radial distributions of the mean and fluctuating velocities, depends considerably on the swirl number.