| The experiment was performed in a at-bottomed cubic tank equipped with a down-pumping3-blade CBY propeller to investigate the liquid turbulence characters of solid-liquid flow in the bottom region by using Two-dimensional Particle Image Velocimetry (2D-PIV) and digital image analysis technique. Liquid flow fields were investigated at four different heights of the paddle away from the tank bottom,10different solid particle concentration and7different particle size of glass beads. Changes of the liquid mean velocity, the turbulent kinetic energy and the turbulent kinetic energy dissipation rate were measured in different experimental conditions.The results show that the speed (N) at which glass beads required to reach critical suspension increase with the height of blade from the bottom (h) increase, N is proportionate to0.381power of h. In the entire measurement area of the flow field at the tank bottom, liquid mean velocity(u) almost constant, u is proportionate to0.0921power of h; turbulent kinetic energy(k) and the turbulent kinetic energy dissipation rate(ε) increase, k and ε is proportionate to0.830and0.312power of h respectively. It can be concluded that the main factors causing the solid in the bottom to reach the critical state of suspension is u of the main stream area.Through the whole measurement area, as the solid particle concentration increased, the liquid phase mean velocity decreased, when the turbulent kinetic energy and turbulent kinetic energy dissipation rate increased after the first stable. Among the three turbulence properties, turbulent kinetic energy dissipation rate was affected most. And the turbulence characteristics mainstream area was affected most among the areas measured in the bottom of the tank.With the increase in particle size of glass beads, the mean speed of the liquid gradually increased both in the entire measurement region and mainstream area where the glass beads placed of the flow field in the groove bottom,... |
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