Particle‐resolved PIV experiments of solid‐liquid mixing in a turbulent stirred tank

Abstract

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.

Eulerian‐Lagrangian simulations of settling and agitated dense solid‐liquid suspensions – achieving grid convergence

“…An important question in this respect is, however, how to judge if model refinement leads to improvement of the level of realism of the simulations. In our opinion we need detailed experiments for this, for example, based on visualization and optical velocity measurements in refractive index matched solid–liquid systems . For example, an experiment along these lines in a mixing tank would be able to decide if the role of the lubrication force is indeed as important as shown by the numerical results in this article, or if there are advantages of using one formulation of a drag force correlation over another.…”

“…After starting the impeller, we keep track of the suspension process and continue beyond the time frame over which quasisteady state is reached. The simulation conditions are chosen such that they are amenable to lab‐scale visualization experiments with refractive index matching of solids and liquid . The impeller‐based Reynolds number is 4000, the Archimedes number associated to particles and liquid is (with g gravitational acceleration, the difference between solid and liquid density, and the kinematic viscosity of the liquid), and the solid‐over‐liquid density ratio is in the range 2.23–2.5.…”

Enhancement of rotating jet by spirally structured vortex tube in centrifugal bladeless mixer flow

“…Particle image velocimetry is a favorable experimental technique to investigate a complicated flow structure in a stirred tank, e.g., the previous papers (Sharp and Adrian, 2001;Escudié et al, 2004;Li et al, 2011Li et al, , 2018 studied the velocity profile by using PIV measurement.…”

Simulations of dense agitated solid–liquid suspensions – Effects of the distribution of particle sizes

“…Laser sheet visualizations supported by refractive index matching would provide critical validation material for the simulation results presented here. Our flow systems have been designed -in terms of solid-over-liquid density ratio and viscosity -with a specific glass and silicone oil refractive index matched system in mind [2]. Furthermore the container has flat walls to facilitate non-deformed optical access.…”

“…Since experimentation in mixing tanks is relatively easy -it is a confined system not necessarily having inlets and outlets and generally allowing for good optical access -they are a means of generating experimental data that are very useful for benchmarking numerical approaches to solid-liquid flow. Specifically experiments that make use of refractive index matching of the solids and liquid phase [1,2] are able to provide a wealth of detailed flow information that can be used for critical assessment of simulations.…”