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湍流扩散多相流在许多工程和环境科学实际应用中十分常见.流体相中的湍流和扩散相的随机本质使得湍流扩散多相流中遇到的问题远比单一流体中遇到的湍流现象复杂得多.首先评述了湍流扩散多相流研究中实验技术和数值计算方面的现状、各自的优点与局限性,以及该领域研究中未来面临的挑战.主要关注湍流扩散多相流研究中以下3方面重点内容:颗粒、液滴和气泡的选择性聚积;湍流对流体相和扩散相耦合作用的影响以及颗粒物和气泡的存在对流体相中湍流的调节机制. 相似文献
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剪切湍流大尺度相干结构的模式研究 总被引:3,自引:0,他引:3
发展了一种计算剪切湍流大尺度相干结构的新模式.该模式的基础是认为大尺度相干结构为湍流场中流体脉动能量增长最快的那部分,且包含大部分的湍流脉动能量.在此基础上。通过对湍流相干能量方程的推演。建立了描述大尺度相干结构的特征控制方程,并应用Chebyshev多项式方法求得湍流相干能量的最大增长率在波数空间的分布,从而获得对应的大尺度相干结构.应用该模式研究了槽流和一自然对流中的大尺度相干结构,得到的近壁区流动结构与实验现象十分接近. 相似文献
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文章以流体科学进入二十一世纪后,在大规模超算、云存储、数据通信和人工智能为支撑的大数据时代背景下,结合目前在复旦大学航空航天系所构建的热流体湍流直接数值仿真数据库,以及复旦大学团队近期与美国德州大学刘超群教授、上海理工大学蔡小舒教授以及国内水动力学杂志编辑部所合作开展的第三代涡识别技术研究,初步概念性地展示旋涡和湍流,特别是针对有工程实际背景和直接应用价值的壁湍流,在这两个流体力学关键基础议题上的最新认知,和基于大数据深度学习的相关湍流工程模拟实践成果.这些成果包括:(1) 基于第三代涡识别技术的尾迹湍流中的涡运动学和动力学探索;(2) 流-热统一完整的类-1、类-2湍流边界层壁面律构建;(3) 基于第三代涡识别量对Kolmogorov 幂次律的再认知;(4) 基于DNS统计数据和神经网络深度学习构建新型湍流封闭模型及RANS计算实践.通过这些成果展示,论证解决这两个基础流体科学议题的技术路径,进而促进流体及相关学科研究在现代大数据背景下取得实质性进展和突破,并惠及现代流体、气动、水利、动力和化工等工程领域. 相似文献
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基于Oldroyd-B型粘弹性流体模型,采用同心旋转圆柱间非线性动力系统分析了流体的弹性对轴对称Taylor涡稳定性的影响.分析结果表明,对于弱弹性流体,Taylor涡出现时,系统存在超临界分岔;而对于强弹性流体则出现亚临界分岔.在小间隙大扰动条件下,采用有限差分法分析了非线性效应对系统稳定性的影响.数值计算结果表明,随着流动速度的增加,润滑油膜的失稳结构与流体的弹性有关,对于弱弹性流,流体以同宿轨道分岔失稳;强弹性流则出现倍周期分岔,直至发生混沌,流场最终发展为湍流. 相似文献
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在我国开展工程湍流研究的设想 总被引:3,自引:0,他引:3
本文包括三部分:1)提出开展工程湍流研究的背景;2)工程湍流研究的特征和内容;3)开展工程湍流研究的设想,其中包括:a)湍流理论的概念鉴别和在工程中的应用,b)湍流模式理论的应用和完善,c)湍流测量和d)湍流控制. 相似文献
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RNGк—ε模式在工程湍流数值计算中的应用 总被引:2,自引:0,他引:2
自Yakhot和Orszag提出RNGк-ε湍流模式以来,很多学者对其进行了修正和发展。并将其应用于某些实际湍流问题的数值模拟。取得了一些与实验近似一致的结果。本文主要从工程湍流计算的角度出发。结合作者的部分研究工作。对近年来RNGк-ε模式在湍流流动数值研究中的应用现状及进展情况进行了总结,指出了该模式存在的问题,并对其应用前景进行了展望。 相似文献
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离心泵叶轮内宾汉流体湍流流场的数值计算 总被引:8,自引:0,他引:8
考虑宾汉流体本构关系特点,建立了任意曲线坐标系(ζ,η)下宾汉流体湍流流动的基本方程,应用压力加权校正算法,实现了速度场和压力场的关联,采用交错网格技术,解决了非物理压力振荡问题,在此基础上,对离心泵叶轮内回转面上宾汉流体湍流流动进行了数值模拟,并分析探讨了离心泵叶轮内宾汉流体湍流流动机理。 相似文献
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非线性湍流模式研究及进展 总被引:6,自引:1,他引:5
现代湍流模式研究已经超出了经典的Boussinesq涡粘性概念和线性的雷诺应力输运范畴,湍流运动过程中的非线性本质已成为模式研究人员所关心的中心问题。其目的在于使湍流模式能更加真实地再现湍流运动的复杂性,提高模式的适用范围,使复杂湍流能够得到合理的模拟,非线性湍流模式在解决复杂湍流运动的计算中已经取得可喜进展,正逐步应用于工程湍流的计算。同时,工程中的湍流问题计算也已走出了简单剪切流动类型及传统的k-ε(及其它形式的)二方程模式框架,二阶矩封闭模式在先进的工程计算中已被用来解决诸如可压缩的空气动力学、发动机气缸及三维复杂几何场内等具有重要应用背景的流动问题,并逐步进入计算流体力学商业软件包。 相似文献
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Particle/droplet/bubble fluctuation and dispersion are important to mixing, heat and mass transfer, combustion and pollutant formation in dispersed multiphase flows, but are insufficiently studied before the 90 years of the last century. In this paper, the present author reports his systematic studies within nearly 20 years on two-phase turbulence in dispersed multiphase flows, including particle fluctuation in dilute gas-particle and bubble-liquid flows, particle-wall collision effect, coexistence of particle turbulence and inter-particle collisions, fluid turbulence modulation due to the particle wake effect and validation of the two-fluid RANS modeling using large-eddy simulation. 相似文献
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The two-fluid model is widely adopted in simulations of dense gas-particle flows in engineering facili- ties. Present two-phase turbulence models for two-fluid modeling are isotropic. However, turbulence in actual gas-particle flows is not isotropic. Moreover, in these models the two-phase velocity correlation is closed using dimensional analysis, leading to discrepancies between the numerical results, theoretical analysis and experiments. To rectify this problem, some two-phase turbulence models were proposed by the authors and are applied to simulate dense gas-particle flows in downers, risers, and horizontal channels; Experimental results validate the simulation results. Among these models the USM-O and the two-scale USM models are shown to give a better account of both anisotropic particle turbulence and particle-particle collision using the transport equation model for the two-phase velocity correlation. 相似文献
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《Particuology》2014
The two-fluid model is widely adopted in simulations of dense gas–particle flows in engineering facilities. Present two-phase turbulence models for two-fluid modeling are isotropic. However, turbulence in actual gas–particle flows is not isotropic. Moreover, in these models the two-phase velocity correlation is closed using dimensional analysis, leading to discrepancies between the numerical results, theoretical analysis and experiments. To rectify this problem, some two-phase turbulence models were proposed by the authors and are applied to simulate dense gas–particle flows in downers, risers, and horizontal channels; Experimental results validate the simulation results. Among these models the USM-Θ and the two-scale USM models are shown to give a better account of both anisotropic particle turbulence and particle–particle collision using the transport equation model for the two-phase velocity correlation. 相似文献
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The standard k-ε model and three low-Reynolds number k-ε models were used to simulate pipe flow with a ring device installed in the near-wall region. Both developing and fully developed turbulent pipe flows have been investigated. Turbulence suppression for fully developed pipe flows revealed by hot-wire measurements has been predicted with all three low-Reynolds number models, and turbulence enhancement has been predicted by the standard k-ε model. All three low-Reynolds number models have predicted similar distributions of velocities, turbulence kinetic energy, and dissipation rate. For developing pipe flows, the region of turbulence suppression predicted by the three low-Reynolds number models is much more extensive (up to 30 pipe diameters downstream of the device) than for full developed flow; whereas the standard k-ε model has only predicted turbulence enhancement. 相似文献
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The basic equations of turbulent gas-solid flows are derived by using the pseudo-fluid model of particle phase with a refined
two-phase turbulence model. These equations are then applied to swirling gas-particle flows for analyzing the collection efficiency
in cyclone separators. 相似文献
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This paper describes a newly developed non-isotropic multiple-scale turbulence model(MS/ASM)for complex flow calculations.This model focuses on the direct modeling of Reynolds stresses and utilizes split-spectrum concepts to model multiple-scale effects in turbulence.Validation studies on free shear flows,rotating flows and recirculating flows show that the current model performs significantly better than the single-scale k-εmodel.The present model is relatively inexpensive in terms of CPU time which makes in suitable for broad engineering flow applications. 相似文献
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统一二阶矩模型用于模拟旋流湍流两相流动 总被引:1,自引:2,他引:1
用统一二阶矩模型(USM)模拟了旋流数为047和15的气粒两相流动,并和实验结果以及k ε kp模型的模拟结果进行了对比.研究结果表明,提高旋流数减小了轴向速度反流区,增大了切向速度似固核区.USM和k ε kp模型预报旋流数为047时的两相速度场差别不大,并都和实验结果接近,但前者预报的旋流数为15的两相速度场比后者有改进,在两种情况下,前者都能揭示出后者无法预报的两相湍流各向异性规律. 相似文献
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Accurate prediction of unsteady separated turbulent flows remains one of the toughest tasks and a practi cal challenge for turbulence modeling. In this paper, a 2D flow past a circular cylinder at Reynolds number 3,900 is numerically investigated by using the technique of unsteady RANS (URANS). Some typical linear and nonlinear eddy viscosity turbulence models (LEVM and NLEVM) and a quadratic explicit algebraic stress model (EASM) are evaluated. Numerical results have shown that a high-performance cubic NLEVM, such as CLS, are superior to the others in simulating turbulent separated flows with unsteady vortex shedding. 相似文献