Morteza Monshizadeh, Ahmad Tahershamsi, Hassan Rahimzadeh, Hamed Sarkardeh,
Volume 17, Issue 8 (10-2017)
Abstract
In the present study, free surface vortex dynamic was experimentally investigated in a horizontal intake. Air entrainment rate into the intake due to the air-core vortices was also discussed. The results presented are the relationship between the vortex type and the intake hydraulic parameters, general pattern of surface displacement of the vortex core and its relation with the vortex type, the required time duration to fully development of the vortex core, and finally evaluation of the vortex induced air entrainment rate. In this research by defining intake number as intake Froude number over the intake relative submergence, a relationship was established between the vortex type and the intake number. Moreover, it was shown that while the intake number increases, surface instability of the vortex core decreases, in which, for the intake numbers greater than one, surface movement of the vortex core is limited to an area of the twice of the intake diameter. Then, another relationship was also established between the time requirement of the vortex air-core formation and the intake number, and it was shown that there will be an exponentially decrease in the mentioned time scale, while the intake number increases. In this context, a relationship was suggested and compared with one of previous works. In the last section, the dependency between air entrainment rate due to the air-core vortices and the intake number was considered, and another relationship was also suggested and compared with previous works.
M. Aghaei, R. Dehghan,
Volume 20, Issue 5 (5-2020)
Abstract
Two-stage centrifugal separators are the last generation of gravity separators for the separation and upgrading of minerals. Gravity upgrading techniques are methods by which a mixture of particles with different dimensions, shapes, and masses can be separated by gravity, centrifugal force, and other forces by the flow of fluid, especially water (or air). The fluid flow inside such separators is always turbulent. The selection of a suitable turbulence model is an important stage for the prediction of the fluid flow pattern in numerical simulation. The purpose of this research was to find the suitable turbulence model for the prediction of hydrodynamic parameters in a two-stage centrifugal separator using computational fluid dynamics (CFD) modeling. For this purpose, multiphase simulation of the separator has been performed using five turbulence model including k-e, renormalization group (RNG k-e) and Reynolds stress model (RSM). Air core pattern, velocity distribution and partition curve of discrete phase were used for evaluation of the effect of turbulence model on the flow field. The results of the CFD simulation were validated using experimental data. The difference between the results of RSM simulation with the experimental results for fluid recovery, air-core size in the first and second stage of separator were 4.73%, 4.3% and 5.2%, respectively. The results of turbulence models of k-e and RNG k-e were not in accordance with the experimental results.
