The Large Eddy Simulation Of Turbulent Flow Field With The Existence Of Single Particle In Cubic Stirred Tank

Solid-liquid mixing operation is widely used in the chemical unit process. Suspension mechanism of the single particle plays a basic theoretical guidance role for solid-liquid system, such as particles transportation in pipeline, river deposition process and etc. It is necessary to analyze the fluid field information for the research on suspension mechanism of the single particle.CFD is short for Computational Fluid Dynamics. At present, Reynolds average method and large eddy simulation method is widely used in solving the fluid flow problem. Compared to Reynolds average method, the large eddy method has the more accurate solution of turbulence kinetic energy. In addition, the latter can get the pulsating information of turbulent fluid flow with time.Among the existing study of turbulent fluid in a stirred tank, it lack the research of the time step, grid number and the macroeconomic instability phenomenon on the effect of time average results obtained by the LES method.With the large eddy simulation method, the CFX software and the CBY axial flow impeller with a diameter of75mm, the turbulent fluid flow was solved in the cubic stirred tank with the side length220mm; the water is used as the working medium. In this paper, the effect of the macro instability phenomenon, the time step and grid number on the time average results obtained by LES method was considered. In the end, it has the following conclusions:First of all, when regardless the effect of macro-instability phenomenon on the time average results obtained by LES, it will lead to a random time average result.Second, the time step and grid number have the common and interact effect on the results with the large eddy simulation. There exists a critical grid number, with which we can acquire a more accurate turbulent flow fluid in a short time.Again, when the speed of the agitator changes a lot, it is necessary to use a different time step and grid number.Finally, the information of turbulent flow fluid with the large eddy simulation method was obtained, and the result of turbulent fluid flow analyzed. The results show that:along the direction of the fluid flow, the turbulent kinetic energy close to the particle has the same value, while the velocity not the same value.