错位六弯叶桨搅拌假塑性流体流场宏观不稳定性数值模拟

采用分离涡模型，对错位六弯叶（6PBT）搅拌槽内流场结构和宏观不稳定性（MI）进行了数值模拟。工作介质分别选用去离子水和不同质量分数的黄原胶水溶液，并将水的速度场分布与PIV实验结果进行了比较。通过采集监测点的速度时间序列，结合MATLAB软件编程，计算得到流场宏观不稳定频率的变化。结果表明：流场结构和速度矢量的计算值与PIV实验数据吻合较好，分离涡模型的计算结果可靠；提高转速，槽内假塑性流体MI频率峰值增大，脉动强度提高，当转速达到225 r·min^-1时，MI频率特征消失，频谱图呈现谱带现象，意味着流场进入混沌；流体的流变性对MI没有影响，MI现象是流体流动的共有特征。

Numerical simulation of macroscopic instability induced by 6PBT impeller in a stirred tank with pseudoplastic fluid

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.