The “end of the vortex” (EoV) phenomenon, a flow instability that plays a crucial role in cyclone design and operation is studied in this article. In the experimental part of the study, tests were carried out to understand the origin and nature of the EoV and to study the effects of the flowrate through, and the length of, the cylindrical cyclone on the EoV. In the theoretical part, computational fluid dynamics (CFD) models, in agreement with the geometrical configurations and operating conditions used in the present and earlier experimental studies, were constructed and investigated. Three‐dimensional simulations were carried out using the large eddy turbulence model with the commercial CFD package Star‐CD. Bending of the vortex core to the wall of the vessel and its precessional motion, constituting the phenomenon of the EoV, was observed in the simulations in most geometries. The results are in a good agreement not only with the present experimental results but also with previous experimental observations. © 2011 American Institute of Chemical Engineers AIChE J, 2012

Abstract. Particle tracks in a hydrocyclone generated both experimentally by positron emission particle tracking (PEPT) and numerically with Eulerian-Lagranian CFD have been studied and compared. A hydrocyclone with a cylinder-on-cone design was used in this study, the geometries used in the CFD simulations and in the experiments being identical. It is shown that it is possible to track a fast-moving particle in a hydrocyclone using PEPT with high temporal and spatial resolutions. The numerical 3-D particle trajectories were generated using the Large Eddy Simulation (LES) turbulence model for the fluid and Lagrangian particle tracking for the particles. The behaviors of the particles were analyzed in detail and were found to be consistent between experiments and CFD simulations. The tracks of the particles are discussed and related to the fluid flow field visualized in the CFD simulations using the cross-sectional static pressure distribution.

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