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本文针对我们已提出的自然循环与低温热管耦合的新型传热元件进行了初步的数值模拟.基于一些合理的假设,利用一维两相流均相动态模型对液氮在自然循环管路中的瞬时换热量进行了计算,在与实验结果进行比较的基础上,得到了一些有关冷却时间与最低冷却温度的初步结论,并对计算结果进行了分析. 相似文献
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可燃悬浮寺燃烧诱导激波可其加速过程研究 总被引:1,自引:0,他引:1
以铝粉为例,基于双流体模型,分别采用TVD格式和MacComack格式计算气相和颗粒相流场,基于Arrihenius定律及管道壁面湍流k-ε模型计算流场反应速度,对水平燃烧管内可燃悬浮粉尘在弱点火条件下激波的产生及加强过程进行了理论分析与数值模拟。研究发现,壁面湍流在火焰加速及燃烧诱导激波过程中起着关键作用,数值计算结果揭示了可燃悬浮粉尘云中压缩波到激波的转捩机制及气固两相流场参数的变化规律。计算 相似文献
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水轮机转轮内部的三维固液两相紊流计算 总被引:4,自引:1,他引:3
1引言本文利用两相流动的多流体模型和k-。-A。两相索流模型计算水轮机转轮内部的三维固液两相紊流。在索流两相流动的多流体即多连续介质模型中,离散相看成是Euler坐标中处理的拟流体。与小滑移和无泪移模型不同的是,多流体模型可以分别考虑大滑移和离散颗粒扩散,其间无直接联系,并且能够充分考虑离散相质量、动量及能量的湍流扩散山本文利用速度压力校正法之一:SIMPLEC法进行数值计算。该法最早使用在S.VPatankar和D.B.Snalding在1972年提出的SIMPLE算法中间,本文将其推广到具有交错网格的非正交贴体坐标系中计算三维… 相似文献
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理论分析了射流抛光的紊动冲击射流特点,构建了射流抛光的垂直冲击射流模型和斜冲击射流模型。根据射流抛光冲击射流的特点,比较各种流体模型后,采用RNG k-e 模型应用于射流抛光模型的计算。利用计算流体力学理论的二阶迎风格式对抛光模型方程离散,用SIMPLEC数值计算方法对射流抛光过程的紊动冲击射流和离散相磨粒分布进行数值模拟,得到了射流抛光过程的连续流场和离散相磨粒与水溶液的耦合流场,同时计算出了抛光液射流在工件壁面上的压力、速度、紊动强度、剪切力分布和磨粒体积质量分布,分析了垂直射流抛光模型和斜冲击射流抛光模型紊流流场的特点。 相似文献
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The Stockmayer fluid is often used to describe a polar fluid. The dipolar Yukawa (DY) fluid is also a useful model for such fluids and is convenient for theoretical applications. Here we use the mean spherical approximation (MSA) and perturbation theory (PT) to study the heat capacities of the DY fluid model of a polar fluid and compare these results with Monte Carlo simulations for this model polar fluid. We find that the DY fluid shows the same features as the Stockmayer fluid does; demonstrating the utility of the DY fluid and further finding that the MSA and PT approaches give reasonably accurate results for the heat capacity. 相似文献
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Jing-Ming Guo Chwan-Hwa Wu 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1996,24(6):1348-1358
The variable radius method is proposed to approximate the radius of the ionization channel in the one and a half-dimensional (1.5-D) fluid models for studying streamer development, in which the unreasonable constant radius in the traditional 1.5-D fluid models is corrected. The streamer development and propagation between the 1.5-D fluid model with the variable radius method and the two-dimensional (2-D) fluid model using the same initial and external conditions are compared. The radius in each stage of streamer development from the 1.5-D fluid model with the variable radius method shows agreement to a certain degree with that of the 2-D fluid model. The purpose of this paper is not to negate the role of the 2-D fluid models, but to explore the potential of the 1.5-D fluid models and make them more useful and accurate as well as to understand the evolution of streamer radius. The streamer development from the 1.5-D fluid model with the variable radius method not only maintains simplicity of the 1.5-D fluid models, but also presents agreement with the 2-D fluid models for streamers 相似文献
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分析了激光在气体中传输时采用等压近似线性方程求解流场密度分布的优缺点,在高低速流场统一计算模型的基础上提出了基于压力原变量的分步求解的弱可压缩流计算模型,并分析了该模型的特点。采用该模型结合标量衍射理论对连续激光在封闭充气管道中受到的气体热效应影响进行了数值仿真。仿真结果与实验结果的对比表明,弱可压缩流计算模型能更精确地反映非自由边界热对流对气体密度分布的影响,进而反映流场对光束的影响。这说明弱可压缩流计算模型能较好地适应内通道光传输问题的仿真研究。 相似文献
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The dynamic droplet model of a critical fluid provides a simple physical model of a critical fluid. We use this to model an emulsion which mimics the Rayleigh linewidth behavior of a critical fluid in the nonhydrodynamic regime. 相似文献
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Satinath Ghosh 《Molecular physics》2013,111(7):868-877
Density functional theory has been applied to investigate the vapor to liquid heterogeneous nucleation on a flat solid surface, by invoking a model free energy density functional along with an exponential density model. The effects of supersaturation of the vapor and the strength of the solid-fluid interaction on the nucleation barrier have been investigated for Lennard–Jones fluid with 12–6 fluid–fluid and 9–3 solid–fluid interaction model. The spinodal decomposition of vapor has been observed at higher supersaturation or at higher strength of the solid–fluid interaction. The shape, density profile and the free energy of formation of droplets of any arbitrary size have been obtained in this work. 相似文献
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多孔介质渗透率的NMR测定 总被引:5,自引:1,他引:4
介绍了利用NMR T2 弛豫数据求取岩心物性参数--渗透率的方法. 国外学者在分析了大量数据的基础上,建立了3种由T2 弛豫数据计算渗透率的模型,分别简称为SDR,Coates-cutoff和Coates-sbvi. 其中SDR模型不受束缚水计算方法的影响,但对岩心孔隙中流体的性质很灵敏,比较适合于水基泥浆地层. coates-cutoff和Coates-sbvi模型对束缚水的计算精度很敏感,可动和不可动流体孔隙体积的测定对渗透率的计算结果影响也很大. 此外,这三种模型对于低渗透率岩石的计算误差都较大. 通过对不同类型岩心的T2 弛豫特性和用常规方法测得的渗透率进行系统分析,在SDR模型的基础上所建立的渗透率测定方法(SDR-REV)有三个可调整参数,计算渗透率适用范围更大,计算的结果与常规实验值更接近. 把SDR-REV方法用于砂岩、砾岩、凝灰岩和火成岩四类岩心样品渗透率的测定,说明SDR-REV方法具有更普遍的适用性. 特别是对于中国普遍存在的低渗透岩心,测定结果更为准确. 相似文献
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E. A. Bogdanov A. A. Kudryavtsev L. D. Tsendin R. R. Arslanbekov V. I. Kolobov V. V. Kudryavtsev 《Technical Physics》2003,48(8):983-994
Results from kinetic and fluid simulations of the positive column plasma of a dc oxygen discharge are compared using commercial
CFDRC software (), which enables one to perform numerical simulations in an arbitrary 3D geometry with the use of both the fluid equations
for all the components (fluid model) and the kinetic equation for the electron energy distribution function (kinetic model).
It is shown that, for both the local and nonlocal regimes of the formation of the electron energy distribution function (EEDF),
the non-Maxwellian EEDF can satisfactorily be approximated by two groups of electrons. This allows one to take into account
kinetic effects within the conventional fluid model in the simplest way by using the proposed two-temperature approximation
of the nonequilibrium and nonlocal EEDF (2T fluid model). 相似文献
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Minseok Song 《Molecular physics》2014,112(20):2658-2664
We perform molecular dynamics simulations to study the transport of geometrically modified water models through channels of carbon nanotube (CNT) membranes. We use two modifications to an existing water model (extended simple point charge SPC/E) as representative surrogates of molecular fluids: (1) bent model (model B) in which the HOH angle is varied while keeping the dipole moment constant by adjusting the OH bond length and (2) modified bent model (model MB) in which the HOH angle changes without any change in OH bond length thereby changing the dipole moment. Interestingly, we find that the fluid transport is a nonmonotonic function of the bond angle for both fluid models. This observed trend is not anticipated based on the fluid density as a function of the bond angle inside and outside of the nanotube channel. However, the average residence time of transmitted molecules through the channel provides an approximately inverse linear correlation with the observed flux, independent of the fluid model. Based on these correlations, we have developed an empirical design parameter connecting fluid transport through CNTs as a function of average occupancy (number of fluid molecules inside the nanotube) and the average residence time. Our results suggest that transport through carbon nanotubes can be sensitive to small changes in the structure of fluid molecules that can potentially be utilised for mixture separation. 相似文献