Angle-Resolved Particle Image Velocimetry Measurements of Flow and Turbulence Fields in Small-Scale Stirred Vessels of Different Mixer Configurations

Abstract

Angle-resolved particle image velocimetry measurements were conducted at one degree intervals in miniature vessels of four different configurations used in high-throughput experimentation. The four vesselsstandard fully baffled, unbaffled, off-center or eccentric impeller, and square sectionwere agitated by an up-pumping six-blade 45° pitched blade turbine (PBT). The effect of periodicity was revealed in all configurations but was restricted to the impeller discharge and inflow regions. The square vessel achieved the strongest axial-radial flow field among all configurations. The smallest overestimation in the computation of turbulent kinetic energy by the ensemble time average method, otherwise referred to as pseudoturbulence, was achieved in the eccentric and square configurations. The up-pumping PBT shed trailing vortices mainly in a radial direction with relatively little axial movement. The highest axial vortex position was achieved in the square vessel, which may be partly responsible for its lower mixing time compared to other configurations. The measurements obtained here in the high-transitional regime suggest that the square configuration performs better than other configurations and can be a good replacement for the fully baffled vessel in commercial high-throughput experimentation units where baffles are usually prohibited. This result was confirmed from mixing time measurements made using planar laser induced fluorescence where the superiority of the square vessel was demonstrated.

Experimentally Validated Computational Fluid Dynamics Simulations of Multicomponent Hydrodynamics and Phase Distribution in Agitated High Solid Fraction Binary Suspensions

“…Among the various flow visualization techniques, laser Doppler velocimetry (LDV) and particle image velocimetry (PIV) have become the most reliable to examine the complex nature of the flow fields in optically transparent, single-phase systems. − These techniques, however, fail completely in dense systems that are opaque, and their application to multiphase flows has, therefore, been restricted to very dilute suspensions . One of the important aspects in the local description of multiphase mixtures is the measurement of phase distribution, which has remained a challenge.…”

Mixing of dense binary suspensions: Multi‐component hydrodynamics and spatial phase distribution by PEPT

“…[1][2][3][4] Among the various flow visualization techniques, laser Doppler velocimetry (LDV) and particle image velocimetry (PIV) have become the most reliable to examine the complex nature of the flow fields in optically transparent singlephase systems. [5][6][7] Application to multi-phase studies, however, has been restricted to extremely dilute suspensions as these techniques fail completely in dense systems which are opaque. 1 One of the important aspects in the local description of multi-phase or multi-component mixtures is the measurement of phase distribution, which has remained a challenge.…”

Lagrangian tools for the analysis of mixing in single‐phase and multiphase flow systems

“…The tracer particle is labeled with a positron-emitting nuclide and the radio isotopes usually used are 18 F, 61 Cu, and 66 Ga. Isotope 18 F has a half-life of 109 min and is produced from either purified water or solid materials under direct bombardment with high energy (33 MeV) 3 He beams via the reactions 16 …”

“…Recently, laser Doppler velocimetry (LDV) or particle image velocimetry (PIV) has been used to examine the complex nature of the flow fields in transparent single-phase systems. [1][2][3] Such approaches have also been reasonably successful at obtaining Eulerian data for the liquid phase in very dilute two-phase systems. 4,5 These optical techniques, however, only provide Eulerian data while mixing is intrinsically a Lagrangian process.…”