Particle Image Velocimetry (PIV) experiments on turbulent solid-liquid stirred tank flow with careful refractive index matching of the two phases have been performed. The spatial resolution of the PIV data is finer than the size of the spherical, uniformly sized solid particles, thereby providing insight in the flow around individual particles. The impeller is a down-pumping pitch-blade turbine. The impeller-based Reynolds number has been fixed to Re 5 10 4 . Overall solids volume fractions up to 8% have been investigated. The PIV experiments are impeller-angle resolved, that is, conditioned on the angular position of the impeller. The two-phase systems are in partially suspended states with an inhomogeneous distribution of solids: high solids loadings near the bottom and near the outer walls of the tank, much less solids in the bulk of the tank. The liquid velocity fields show very strong phase coupling effects with the particles increasingly attenuating the overall circulation patterns as well as the liquid velocity fluctuation levels when the solids volume fraction is increased.
Solids suspension in a stirred tank with a down-pumping pitched-blade turbine impeller has been investigated by using particle image velocimetry (PIV) experiments as well as direct numerical simulations (DNS) with a lattice-Boltzmann (LB) method. The flow regime of this solid-liquid two-phase system is transitional with the impeller-based Reynolds numbers Re = 1334. The refractive index matching (RIM) method is applied in the experiments. The overall solids volume fractions are up to 8% in the experiments as well as in the simulations. The liquid flow fields around the particles are highly resolved in both experimental and simulated cases which makes it possible to investigate solid-liquid interactions in detail. The average distributions of the solids over the tank volume as predicted by the simulations are in good agreement with the experimental results. It is shown that the presence of particles reduces the average velocities as well as the turbulent fluctuation levels of the liquid in both the experiments and simulations although the reduction in the simulations is weaker as compared to in the experiments.
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