涡轮桨搅拌槽内混合过程的大涡模拟

Large Eddy Simulation of Mixing Process in Stirred Tank with Rushton Turbine

在FLUENT 6.1软件平台和网络并行计算硬件平台上,采用大涡模拟(LES)的方法对涡轮桨搅拌槽内的混合过程进行了数值模拟。利用滤波函数对N av ier-Stokes方程进行空间滤波,对大尺寸的涡直接进行求解,而被滤掉的比网格小的旋涡通过Sam agorinsky-L illy亚格子模型求解,对搅拌桨区域采用滑移网格技术。结果表明:大涡模拟对尾涡的预报优于雷诺平均(RAN S)方法,混合时间以及示踪剂响应曲线模拟结果和实验结果吻合较好,且优于RAN S方法。大涡模拟方法为准确预测搅拌槽内湍流流动的非稳态及周期性脉动特性提供了一种有效的工具。

Large eddy simulation （LES） of mixing process in a stirred tank of 0. 476 m diameter with a standard Rushton turbine were reported. The turbulent flow field and mixing time were calculated using LES with Smagorinsky-Lilly sub grid scale model. The impeller was modeled using the sliding mesh technique. Better agreement of mixing time is obtained between the experimental results and prediction by LES than that by the traditional Reynolds-averaged Navier-Stokes （RANS） approach. The response curve of tracer predicted by LES is in a good agreement with the experimental results. The results show that LES is a good approach to investigate unsteady and quasi-periodic behavior of the turbulent flows in stirred tanks.