Isolated mixing region often appears in the high-viscosity fluid with laminar flow in a stirred vessel

reducing fluid mixing efficiency. Diminishing or eliminating isolated mixing region improves the mixing efficiency and reduces mixing energy consumption. Experimental and computational studies were carried out to compare the flow field structures with rigid Rushton turbine impeller (rigid RT impeller) and rigid-flexible Rushton turbine impeller (combination RT impeller). Analyses were carried out on axial

radial and tangential velocity vector plots

velocity contours and velocity distribution scatter plots at the same time power consumption (3 kW·m-3）with these two impellers. Results show that the energy concentrates at the tip of rigid RT impeller and the fluid velocity away from the impeller is small

even at 0 m·s-1

while for combination RT impeller

the energy distributes well in the stirred tank so that the fluid gains certain velocity everywhere. The numerical simulation results agree with experimental results. The combination RT impeller improves mixing efficiency by eliminating isolated mixing regions

while rigid RT impeller presents a poor mixing efficiency since isolated mixing regions always exist.