Philadelphia Mixing Solutions Ltd., Palmyra, Pennsylvania 17078, United States.
Environ Sci Technol. 2010 Dec 1;44(23):8989-95. doi: 10.1021/es1010016. Epub 2010 Nov 3.
In this paper, 12 turbulence models for single-phase non-newtonian fluid flow in a pipe are evaluated by comparing the frictional pressure drops obtained from computational fluid dynamics (CFD) with those from three friction factor correlations. The turbulence models studied are (1) three high-Reynolds-number k-ε models, (2) six low-Reynolds-number k-ε models, (3) two k-ω models, and (4) the Reynolds stress model. The simulation results indicate that the Chang-Hsieh-Chen version of the low-Reynolds-number k-ε model performs better than the other models in predicting the frictional pressure drops while the standard k-ω model has an acceptable accuracy and a low computing cost. In the model applications, CFD simulation of mixing in a full-scale anaerobic digester with pumped circulation is performed to propose an improvement in the effective mixing standards recommended by the U.S. EPA based on the effect of rheology on the flow fields. Characterization of the velocity gradient is conducted to quantify the growth or breakage of an assumed floc size. Placement of two discharge nozzles in the digester is analyzed to show that spacing two nozzles 180° apart with each one discharging at an angle of 45° off the wall is the most efficient. Moreover, the similarity rules of geometry and mixing energy are checked for scaling up the digester.
本文通过将计算流体动力学 (CFD) 得到的摩擦压降与三个摩擦因子关联式得到的摩擦压降进行比较，评估了 12 种用于管内单相非牛顿流体流动的湍流模型。所研究的湍流模型包括 (1) 三个高雷诺数 k-ε 模型，(2) 六个低雷诺数 k-ε 模型，(3) 两个 k-ω 模型，以及 (4) 雷诺应力模型。模拟结果表明，在预测摩擦压降方面，低雷诺数 k-ε 模型的 Chang-Hsieh-Chen 版本比其他模型表现更好，而标准 k-ω 模型具有可接受的准确性和较低的计算成本。在模型应用中，对带有泵送循环的全尺寸厌氧消化器中的混合进行 CFD 模拟，根据流变学对流场的影响，提出对美国环保署推荐的有效混合标准的改进。对速度梯度进行了特征描述，以量化假定絮体尺寸的生长或破裂。分析了在消化器中放置两个排放喷嘴的情况，结果表明，将两个喷嘴以 180°间隔放置，每个喷嘴以 45°角偏离壁面排放，是最有效的。此外，还检查了几何形状和混合能量的相似规则，以对消化器进行放大。
