The flow field structure and macroscopic instability (MI) in a stirred tank equipped with the perturbed six-bent-bladed turbine (6PBT) were numerically simulated by using CFD combined with the detached eddy model. The test fluids used were tap water and xanthan gum solution with different quality fraction

respectively. The numerical results of water velocity distributions were compared with the experimental data obtained by particle image velocimetry (PIV). The distributions of the MI frequency in stirring xanthan gum solution were analyzed by programming combined with the software MATLAB. The results show that the flow field structure and calculated values of the velocity components are in good agreement with the PIV measured data

which validates the detached eddy model. The peak value of MI frequency increases with the increase of the speed

which means the high pulse intensity of flow field. As the speed climes to 225 r·min-1

the peak characteristics of MI frequency disappear and a multi-scale wavelet structure appears

which characterizes that the flow field enters chaos. Moreover

the fluid rheology has less effect on MI frequency

which indicates that the MI phenomenon is a common feature of fluid flow.