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题名	显式代数应力模型模拟搅拌槽内多相流动
作者	冯鑫
学位类别	博士
答辩日期	2012-05-21
授予单位	中国科学院研究生院
导师	杨超
关键词	显式代数应力模型 搅拌槽 湍流 数值模拟 多相流动
其他题名	Numerical simulation of multiphase flow in stirred tanks with an explicit algebraic stress model
学位专业	化学工程
中文摘要	搅拌槽内的多相湍流是反应器工程放大研究的基础问题。多相湍流的实验研究在分散相相含率较高的情况下受到很大的限制，而常见的湍流模拟方法在多相搅拌槽的湍流模拟中也存在一定的缺陷。针对这种情况，本文开发了适用于多相搅拌槽模拟的显式代数应力湍流模型，为多相反应器的工程研究提供了一种新的方法。本文将单相显式代数应力模型应用到搅拌槽的湍流模拟中，并基于一些简化思想将单相模型扩展为两相模型，与欧拉-欧拉多流体模型相结合，开发出适用于搅拌槽内多相流动模拟的两相显式代数应力模型。分别对搅拌槽内的固液、液液、气液两相体系进行了数值模拟，定量地预测了平均速度、脉动速度、湍流动能、相含率分布等。通过预测结果与实验数据的比较，验证了两相显式代数应力模型的准确性，同时也与文献中的k-ε模型和大涡模拟的结果进行了对比。结果表明，两相显式代数应力模型可以很好地预测多相搅拌槽内的流场和相含率分布，预测精度要优于k-ε模型。对比了Gatski & Sepziale三基底、Gatski & Sepziale五基底和Wallin & Johansson五基底三种显式代数应力模型在搅拌槽单相模拟中的应用情况。结果表明，在收敛性方面，Wallin & Johansson五基底模型数值稳定性最好，解的残差最小。在流场的定量对比上，五基底模型的预测结果与实验数据更为吻合。总的来看，具有各向异性特性的Wallin & Johansson三维五基底显式代数应力模型非常适合于搅拌槽单相湍流的数值模拟。应用Wallin & Johansson三维五基底显式代数应力模型对无挡板和带挡板搅拌槽内的单相流动进行了模拟。定量预测的关键参量与文献中报道的实验数据以及其它湍流模型如标准k-ε模型、代数应力模型、雷诺应力模型、大涡模拟等的模拟结果进行了对比，对显式代数应力模型进行了全面的评估。结果表明，显式代数应力模型的计算量与标准k-ε模型相当，远低于大涡模拟和雷诺应力模型；而在平均速度的预测上，显式代数应力模型对峰值和趋势的预测优于标准k-ε 模型，与大涡模拟的结果相近。
英文摘要	Multiphase flow in stirred tanks is fundamental to investigation of industrial reactors scale-up. Experimental study of multiphase flow is subjected to technical difficulty when high phase holdup systems are encountered. Besides, the common turbulence modeling approaches have also shortcomings for modeling turbulent flow in multiphase stirred tanks. Consequently, explicit algebraic stress models (EASM) are developed in this dissertation to numerically study multiphase flow in stirred tanks, which also provides a new method for industrial study of multiphase reactors. In this dissertation, an explicit algebraic stress model is employed to simulate turbulent flow in stirred tanks. Based on some simplifications, the single phase EASM is extended to develop a two-phase EASM based on an Eulerian-Euleran two-fluid approach for simulating multiphase flow in stirred tanks. After that, solid-liquid, liquid-liquid and gas-liquid systems in stirred tanks are numerically studied in terms of quantitative predictions of velocity, turbulence quantities and phase holdup distributions. Validation of such a model is conducted by comparing with the reported experimental data and k-εmodel or LES predictions in the literature. The results show that the two-phase EASM can predict well the flow field and holdup distributions in multiphase stirred tanks, and performs better than the k-εmodel. Gatski & Speziale three-based, Gatski & Speziale five-based and Wallin & Johansson five-based EASMs are used and compared in simulating single phase flow in stirred tanks. The results show that the Wallin & Johansson five-based EASM can ensure the best numerical stability, in which the residuals can drop to the lowest level. Concerning the quantitative comparison of flow field, the peak values of velocity components predicted by the five-based EASM are closer to the experimental data than those predicted by the three-base model. Generally speaking, the anisotropic Wallin & Johansson five-based EASM is quite suitable for simulating turbulent flow in stirred tanks. The Wallin & Johansson five-based EASM is employed to predict single phase flow in baffled and unbaffled stirred tanks. Quantitative predictions of the EASM are compared with the reported experimental data and the predicted results by other turbulence models such as standard k-ε model, algebraic stress model (ASM), Reynolds stress model (RSM) and large eddy simulation (LES) in order to make a comprehensive assessment of such an EASM model. It is concluded that the computational cost of EASM is close to that of the standard k-εmodel, and greatly lower than that of LES and RSM. Concerning the predictions of mean velocities, the EASM is consistently superior to the standard k-εmodel and close to that of the LES.
语种	中文
公开日期	2013-09-25
内容类型	学位论文
源URL	[http://ir.ipe.ac.cn/handle/122111/1860]
专题	过程工程研究所_研究所（批量导入）
推荐引用方式 GB/T 7714	冯鑫. 显式代数应力模型模拟搅拌槽内多相流动[D]. 中国科学院研究生院. 2012.

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