Investigation on the flow characteristics of a novel multi‐blade combined agitator by time‐resolved particle image velocimetry and large eddy simulation

Abstract

We investigated the flow characteristics in a tank of H/T = 1.5 stirred by a novel multi‐blade combined agitator (MBC) by using time‐resolved particle image velocimetry and large eddy simulation approach. The predictions were assessed by Y+ values, Taylor microscale and power spectrum analysis, as well as experimental validation of velocity distributions. Results demonstrate that the MBC agitator can load the energy into the system effectively with a power number of 12.5 in a turbulent regime, resulting in improved axial and radial mass exchange. The upper and lower short blades produce an axial down‐flow in the top half and an axial up‐flow in the bottom half, respectively. Part of axial flows change to radial flows by the radial pumping of the long blades, meanwhile, the impingement of two axial flows improves the axial mass exchange. These flow characteristics lead to an obvious improvement in the turbulent kinetic energy distribution uniformity with higher turbulent intensity.

Numerical Investigation of Particle Suspensions in a Liquid–Solid Stirred Tank with Baffles

“…In this work, the transient flow field was simulated by two methods, the standard k –ε model and LES. In LES, the standard k –ε model and MRF method were first used to obtain steady-state results, and then LES and SG methods were used to do transient simulation . It took a time step for the impeller to rotate 5°, and the time step was found , to have little effect on results with the convergence residual (≤10 –4 ).…”

“…In LES, the standard k−ε model and MRF method were first used to obtain steadystate results, and then LES and SG methods were used to do transient simulation. 54 It took a time step for the impeller to rotate 5°, and the time step was found 34,48 to have little effect on results with the convergence residual (≤10 −4 ). This simulation was performed in the transient mode for 20 rotations to approach the quasi-steady state, and then the transient data were recorded in 10 rotations for the statistical average.…”