各向异性k-ε湍流模型在Rushton桨搅拌槽三维流场整体数值模拟中的应用

根据搅拌槽内的流动呈各向异性的特点 ,引入适用于强旋转流场的各向异性k -ε湍流模型 ,用改进的内外迭代法对有挡板的Rushton桨搅拌槽进行了整体数值模拟 .利用文献中对搅拌槽内流场测定结果 ,给出了适用于Rushton桨搅拌槽的各向异性湍流黏度系数值 .模拟计算得到了搅拌槽内的流场分布和脉动速度分布 ,并同标准k -ε湍流模型计算结果及文献数据进行比较 .结果表明 ,各向异性k -ε湍流模型能成功反映Reynolds应力、湍流动能等湍流特征量 ,明显优于标准k -ε湍流模型 .     

用各向异性代数应力模型数值模拟搅拌槽中的三维全流场

In accordance to the anisotropic feature of turbulent flow, an anisotropic algebraic stress model is adopted to predict the turbulent flow field and turbulent characteristics generated by a Rushton disc turbine with the improved inner-outer iterative procedure. The predicted turbulent flow is compared with experimental data and the simulation by the standard κ-ε turbulence model. The anisotropic algebraic stress model is found to give better prediction than the standard κ-ε turbulence model. The predicted turbulent flow field is in accordance to experimental data and the trend of the turbulence intensity can be effectively reflected in the simulation. The distribution of turbulent shear rate in the stirred tanks was simulated with the established numerical procedure.     

轴流桨搅拌槽三维流场数值模拟

利用k -ε湍流模型预测了搅拌槽在不同操作条件下宏观速度场 ,模型成功预测了搅拌槽内速度分布 ,计算结果与实验结果吻合较好 .模型预测结果表明 ,搅拌槽内宏观流动场受搅拌桨槽径比影响较大 .对单层搅拌桨 -槽体系 ,挡板前后宏观流动场差别很大 ,在挡板以前区域 ,轴向流动较强 ,在整个r -z断面上形成一个整体循环 ;而在挡板后面区域 ,流体在桨叶安装位置高度附近转向轴心流动 ,槽体上半部区域形成二次循环区域 ,且二次循环区域内流体以向下流动为主 .     

用改进的内外迭代法数值模拟Rushton涡轮搅拌槽流场

在有挡板的搅拌槽中，受搅拌桨驱动的液体在挡板的作用下会产生复杂的三维湍流流动.利用“快照”法思路和改进的内外迭代法及k–e湍流模型对Rushton涡轮有挡板的搅拌槽进行了整体数值模拟. 同文献中的实验数据进行了比较，模拟值同实验值基本吻合. 改进后的内外迭代法不依赖经验公式和实验数据，有一定的通用性.     

Rushton桨搅拌槽中气液两相流动的全流场数值模拟

The gas-liquid flow field in a stirred tank with a Rushton disk turbine,including the impeller region,was numerically simulated using the improved inner-outer iterative procedure.The characteristic features of the strirred tank,such as gas cavity and accumulation of gas at the two sides of wall baffles,can be captured by the simulation.The simulated results agree well with available experimental data.Since the improved inner-outer iterative algorithm demands no empirical formula and experimental data for the impeller region,and the approach seems generally applicable for simulating gas-liquid stirred tanks.     

搅拌槽内单相湍流流场数值模拟研究进展

搅拌槽内的流场是决定混合、传热及传质等操作的基础,对流场的研究具有十分重要的意义,计算流体动力学是研究流场的重要方法。本文回顾了搅拌数值模型的发展历程,阐述了三十年来各种搅拌流场数值模拟方法的特点及其应用情况,对比分析了各种湍流模型的优缺点,并展望了未来搅拌槽内单相湍流模型的发展方向。     

搅拌槽内湍流流场的数值模拟

搅拌槽在过程工业中的应用非常广泛,对搅拌槽内流场的研究具有十分重要的意义。实验研究方法具有局限性,基于计算流体动力学的数值模拟方法是研究流场的重要方法。文中介绍了搅拌流场的数值模拟方法和湍流模型,分析了各自的特点及其应用情况,总结了搅拌模拟时边界条件的处理情况,并指出了未来的发展方向。     

搅拌槽内三维流场的数值模拟

应用商业计算流体力学软件CFX对搅拌槽内的流场进行了模拟,并与PIV测试结果进行了比较,流型吻合良好.速度分量的对比结果表明不同情况与各种模型的吻合情况不尽相同,标准k-ε双方程模型、RNG k-ε模型和代数应力模型在主流域内都能较准确地模拟搅拌槽内的流动场.     

应用SST k-ω湍流模型计算Rushton搅拌釜流场

应用SSTkω-湍流模型对Rushton搅拌釜流场进行了计算,并与文献报道实验数据以及标准k-ε模型、RNGkω-模型预测结果进行了比较。结果表明SSTkω-模型所计算的排除流量准数与实验值相差较小,桨叶区速度场与实验数据吻合较好,略优于标准k-ε模型,同时也给出了近壁区的计算结果。在湍动动能的预报上,SSTk-ω模型值与标准k-ε模型比较接近,优于RNGkε-模型,但与实验值都还不同程度地存在着一些差异。     

两种不同挡板的双层桨搅拌槽三维流场数值模拟

采用CFD方法分别对三角形挡板和长方体空心挡板的双层斜直叶桨搅拌槽在水中产生的三维流场进行数值模拟,选取多重参考系法和标准k-ε湍流模型进行模拟,对两者的轴向平面速度场和时均速度分布进行了详细的对比分析,研究结果对搅拌槽的设计和实际应用具有重要的参考价值。     

螺旋桨搅拌槽内湍流参数

在直径494和1600mm的平底有机玻璃槽内,利用一维恒温热膜风速仪测量了7种不同搅拌桨-槽体系中流体的时均速度、脉动速度、能谱函数、微分尺度以及湍流耗散等,对螺旋桨搅拌槽内湍流参数分布进行了详细的描述,研究了叶轮叶端安放角及离底距离对流动场的影响,并分析了放大过程对流动场的影响。     

多层搅拌桨流动场的测量与数值模拟

应用商业计算流体力学软件CFX对搅拌槽内多层搅拌桨的流场进行了模拟,并与LDV测试结果进行了比较.低Reynolds数k-ε模型和代数应力模型流型吻合较好;标准k-ε双方程模型和RNG k-ε模型下层桨流场出现不同程度的扭曲,与实验测试结果不符.速度分量的对比结果表明,低Reynolds数k-ε模型和代数应力模型能较准确地模拟搅拌槽内的流动场,其中尤以代数应力模型最为准确.     

NUMERICAL SIMULATION OF LAMINAR SOLID-LIQUID TWO-PHASE FLOW IN STIRRED TANKS

Laminar flow of solid-liquid suspension has been rarely reported in the literature. In this article, the laminar solid-liquid two-phase flow in a lab-scale stirred tank is measured with digital particle image velocimetry (DPIV) and numerically simulated with the improved inner-outer iterative method. The simulation results show good agreement with the present data. In the range of low solid volume concentration under investigation, solid particles have minor impact on two-phase flow, and the simulated flow fields of both phases are similar to the counterpart of single-phase laminar liquid flow. The comparison of simulation with experiments of single-phase laminar flow shows reasonable agreement. These observations suggest that the numerical method employed in the present study is reliable for analysis of stirred tanks. The influence of impeller off-bottom clearance on velocities is found significant: the lower the impeller, the smaller the radial and axial velocities, and the higher the solid concentration.     

STUDY OF THE TURBULENT FLOW IN AN UNBAFFLED STIRRED TANK BY DETACHED EDDY SIMULATION

Detached eddy simulation (DES) of the liquid-phase turbulent flow in an unbaffled stirred tank agitated by a six-blade, 45°-pitched blade turbine was performed in this study. The tank wall is cylindrical with no baffle and the fluid flow problem was solved in a single reference frame (SRF) rotating with the impeller. For the purpose of comparison, computation based on large eddy simulation (LES) was also carried out. The commercial code Fluent was used for all simulations. Predictions of the phase-averaged turbulent flow quantities and power consumption were conducted. Results obtained by DES were compared with experimental laser Doppler velocimetry (LDV) data from the literature and with the predictions obtained by LES. It was found that numerical results of mean velocity and turbulent kinetic energy profiles as well as the power consumption are in good agreement with the LDV data. When performed on the same computational grid, which is under-resolved in the sense of LES, DES allows better accuracy than LES in that it works better in the boundary layers on the surface of the impeller and the stirred tank walls. It can be concluded that DES has the potential to predict accurately the turbulent flow in stirred tanks and can be used as an effective tool to study the hydrodynamics in stirred tanks.     

CFD模型在污水沉淀池数值模拟中的应用

本文介绍了沉淀池数值模拟中所运用的大量紊流模型,综述了计算流体力学（CFD）模型应用于污水沉淀池数值模拟的研究现状,讨论了不同边界条件、环境因素对模拟结果的影响,评述了CFC模型应用于污水沉淀池数值模拟的优劣.     

搅拌槽内黏性流体流动的DPIV测量与CFD模拟

搅拌槽是化学工业及其相关工业广泛应用的设备之一,由于其内部流动的复杂性,搅拌混合操作目前尚未形成完善的理论体系．对搅拌槽的设计和放大,主要是依赖半经验的方法,对其内部流场有必要进行更深入的研究．目前对不同黏性流体的流动测量及计算流体力学模拟工作见诸报道较少,而     

管壳式换热器壳程流动和传热的三维数值模拟

提出了一种管壳式换热器壳程单相流动和传热的三维模拟方法 .用体积多孔度、表面渗透度、分布阻力和分布热源来考虑壳程复杂几何结构造成的流道缩小和流动阻力、传热效应 ,通过数值求解平均的流体质量、动量、能量守恒方程 ,得到壳程流动和换热的分布 .用该方法对一实验换热器进行了流动和传热的模拟 ,计算结果和实验结果吻合良好 .