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为优化搅拌槽体型设计、提高搅拌效率,分别利用气液两相大涡模型和标准k-ε紊流模型,结合多参考系法,对搅拌槽内的气液混合过程进行了模拟计算;控制方程的离散使用了有限体积法;速度与压力耦合求解时使用了压力隐式算子分裂PISO(Pressure-Implicit with Splitting of Operators)算法;模拟自由水面采用了VOF(Volume of Fluid)法;通过计算得到了搅拌槽在相同通气率、不同转轮转速下的气液流动速度场以及不同截面含气率的分布规律。比较两种模型,模拟结果表明:叶片旋转区域紊流的各向异性随着转速的增加而明显加强;基于各向同性假设的标准k-ε紊流模型不能描述流体流速的波动变化,而大涡模拟能够捕捉叶片附近区域流场的分布规律;在通气率一定的情况下,转轮转速的大小对下叶轮附近区域的含气率影响较小,而对上叶轮附近区域含气率的影响较大。
In order to optimize the design of the stirred tank body and improve the mixing efficiency, the gas-liquid mixing process in the stirred tank was simulated by using the large-eddy-vortex model and the standard k-ε turbulence model respectively and the multi-reference system. The finite volume method is used for the discretization of the equations; Pressure-Implicit with Splitting of Operators (PISO) method is used to solve the coupling of velocity and pressure; the VOF (Volume of Fluid) method is used to simulate the free surface; The distribution law of the gas-liquid velocity field and the gas content of different cross-sections under the same aeration rate and rotation speed was obtained. The simulation results show that the anisotropy of turbulent flow in the rotating region of blades is obviously enhanced with the increase of rotating speed. The standard k-ε turbulence model based on the assumption of isotropy can not describe the variation of the flow velocity of the fluid, The eddy simulation can capture the distribution of the flow field in the vicinity of the blade. When the ventilation rate is constant, the rotation speed of the rotor has less influence on the gas content in the vicinity of the lower impeller, but the effect on the gas content in the vicinity of the upper impeller Larger.