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1.
INTRODUCTION Oil-gas multiphase transport technology, in- cluding multiphase pressurization, multiphase flow- meter and multiphase flow control, has become very effective as an economic and reliable method for seabed oil exploitation. During the design of mixing transport system, prediction of pressure drop, heat transfer coefficients and void fraction is needed, so flow pattern identification is necessary. Among flow parameters, void fraction, defined as the cross section fraction occupie… 相似文献
2.
轴流管壳式换热器壳侧流体优化分布数值研究 总被引：1，自引：0，他引：1
针对大型、超大型轴流管壳式换热器壳侧流体的流动分布不均的问题,提出在进出口处增加流体分布挡板用以改进流体分布不均的现象.并且在此之前的理论研究基础上,采用多孔介质--分布阻力模型,对不同结构参教的流体分布挡板进行教值模拟研究,研完结果表明,在壳侧进出口安装流体分布挡板能够有效促进流体的均匀分布,理论分析的教学模型与数值研完结果表现为一致,通过几种不同的结构参数分布挡板的数值结果对比,表明采用第三种结构形式的挡板不但流体分布均匀,而且由于挡板存在所造成的压力损失最小. 相似文献
3.
A specialised electrochemical measurement cell was plugged into a pilot water distribution system to simulate the pipe inner-wall corrosion. The linear polarisation resistance(LPR) technique and electrochemical impedance spectroscopy(EIS) were measured in real time to study the variation of the corrosion rate(CR) and scale of cast iron. Three corrosion stages were observed according to the LPR analysis: an initial stage with significantly fluctuating CR, a developmental stage with slowly decreasing CR, and a stable stage with a low CR of approximately 0.157 5 mm·a~(-1). The EIS revealed that the scales with a compact outer layer and a porous inner layer finally formed in the stable stage, and the polarisation resistance was approximately 2 175 ?·cm~2. A physicochemical analysis of the scales showed that ferric oxides, oxyhydroxides and calcite made the outer layer compact and effectively limited the diffusion of oxygen through the scales, which resulted in a low CR. 相似文献
4.
A mathematic model of two-phase flow and a physical model of two-dimensional (2D) vertical section for the plate-type structured packing Mellapak 250.Y were set up and verified. The models were used to study the influence of packing’s surface microstructure on the continuity of liquid film and the amount of liquid holdup. Simulation results show that the round corner shape and micro wavy structure are favorable in remaining the continuity of liquid film and increasing the amount of liquid holdup. The appropriate liquid flow rate was determined by investigating different liquid loadings to obtain an unbroken liquid film on the packing surface. The pressure difference between inlet and outlet for gas phase allowed gas and liquid to flow countercurrently in a 2D computational domain. The direction change of gas flow occurred near the phase interface area. 相似文献
5.
The influence of sandstorms on train aerodynamic performance and safe running was studied in response to the frequent occurrence
of sandstorm weather in north China. An Eulerian two-phase model in the computational fluid dynamic (CFD) software FLUENT,
validated with published data, was used to solve the gas-solid multiphase flow of a sandstorm around a train. The train aerodynamic
performance under different sandstorm levels and no sand conditions was then simulated. Results showed that in sandstorm weather,
the drag, lift, side forces and overturning moment increase by variable degrees. Based on a numerical analysis of aerodynamic
characteristics, an equation of train stability was also derived using the theory of moment balance from the view of dynamics.
A recommended speed limit of a train under different sandstorm levels was calculated based on the stability analysis. 相似文献
6.
Numerical investigation on the phase change of water-saturated porous media with thermosyphon 总被引：1，自引：0，他引：1
Numerical investigations were carried out to determine the coupled heat transfer of water-saturated porous media with a two-phase
closed thermosyphon for soil freezing, and to examine the characteristics of the freezing heat transfer in the water-saturated
porous media. The whole control volume includes the thermosyphon and the porous media. The two-dimensional governing equations
for the water-saturated porous media are used.
The conjugation of heat transfer between the thermosyphon and porous media is reflected through thermal balance between the
thermosyphon and the porous media.
The finite-difference method was used to solve the two-dimensional goverming equation, for the water-saturated porous media
and the heat transfer characteristics of the thermosyphon, obtain the flow fields and the temperature distributions in the
soil. This paper deals mainly with the effect of some factors (such as soil properties, climate and thermosyphon dimensions)
on the heat transfer rate of the thermosyphon and the growth of the freezing front. The predictions of the present study agree
well with the measured data. 相似文献
7.
Gas-liquid two-phase flow and heat transfer can be encountered in numerous fields, such as chemical engineering, refrigeration, nuclear power reactor, metallurgical industry, spaceflight. Its critical heat flux （CHF） is one of the most important factors for the system security of engineering applications. Since annular flow is the most common flow pattern in gas-liquid two-phase flow, predicting CHF of annular two-phase flow is more significant. Many studies have shown that the liquid film dryout model is successful for that prediction, and determining the following parameters will exert predominant effects on the accuracy of this model： onset of annular flow, inception criterion for droplets entrainment, entrainment fraction, droplets deposition and entrainment rates. The main theoretical results achieved on the above five parameters are reviewed; also, limitations in the existing studies and problems for further research are discussed. 相似文献
8.
Gas-liquid two-phase flow and heat transfer can be encountered in numerous fields, such as chemical engineering, refrigeration, nuclear power reactor, metallurgical industry, spaceflight. Its critical heat flux (CHF) is one of the most important factors for the system security of engineering applications. Since annular flow is the most common flow pattern in gas-liquid two-phase flow, predicting CHF of annular two-phase flow is more significant. Many studies have shown that the liquid film dryout model is successful for that prediction, and determining the following parameters will exert predominant effects on the accuracy of this model: onset of annular flow, inception criterion for droplets entrainment, entrainment fraction, droplets deposi-tion and entrainment rates. The main theoretical results achieved on the above five parameters are reviewed; also, limitations in the existing studies and problems for further research are discussed. 相似文献
9.
The authors give the solution to the problem of one-dimensional consolidation of double-layered ground with the use of the
differential quadrature method. Case studies showed that the computational results for pore-water pressure in soil layer agreed
with those of analytical solution; and that in the computational results for the interface of soil layer also agreed with
those of the analytical solution except for the small discrepancies during shortly after the start of computation. The advantages
of the solution presented in this paper are that compared with the analytical solution, it avoids the cumbersome work in solving
the transcendental equation for eigenvalues, and in the case of the Laplace transform solution, it can resolve the precision
problem in the numerical solution of long time inverse Laplace transform. Because of the matrix form of the solution in this
paper, it is convenient for formulating computational program for engineering practice. The formulas for calculating double-layered
ground consolidation may be easily extended to the case of multi-layered soils.
Project (No. RC9609) supported by the Zhejiang Provincial Natural Science Foundation of China 相似文献
10.
以聚氨酯泡沫为试样,建立了多孔介质水平燃料床阴燃的二维两相流数学模型.模型包括燃料吸热热解、燃料放热氧化及焦炭的放热氧化3个反应过程.通过有限单元法对聚氨脂泡沫的阴燃控制方程进行离散,并采用数值分析软件包FEMLAB进行计算求解.数值模拟了来流速度为0.28 cm/s时燃料阴燃的温度分布和固体成分(燃料泡沫、炭粒和灰分)的变化,其中阴燃传播平均速度为0.0214cm/s,阴燃最高温度平均为644.67K;固体成分的变化曲线明显的将填充床分成4个区域:未燃区、燃料热解氧化区、焦炭氧化区及燃料燃尽区.同时,模拟研究了来流速度及燃料特性参数(导热率、比热、密度、孔隙直径等)对阴燃传播特性的影响.结果表明:阴燃速度和阴燃温度随着来流速度的增大基本上呈线性增长;燃料密度对阴燃传播影响最大;对于孔径较大的多孔介质燃料,模型中要考虑辐射的影响.模拟数据与实验数据进行了对比,结果基本吻合. 相似文献
11.
Biot's two-phase theory for fluid-saturated porous media was applied in a study carried out to investigate the influence of water saturation on propagation of elastic wave in transversely isotropic nearly saturated soil. The characteristic equations for wave propagation were derived and solved analytically. The results showed that there are four waves: the first and second quasi-longitudinal waves (QP1 and QP2), the quasi-transverse wave (QSV) and the anti-plane transverse wave (SH). Numerical results are given to illustrate the influence of saturation on the velocity, dispersion and attenuation of the four body waves. Some typical numerical results are discussed and plotted. The results can be meaningful for soil dynamics and earthquake engineering. 相似文献
12.
Rechargeablealkalinenickelbatteries (e.g.,Ni/Cd ,Ni/Fe,Ni/Zn,Ni/H2 andNi/MH)areusuallypos itivelimited ,sothatthecapacityandcyclelifeofthecellsaredeterminedmainlybytheperformancesofnickelelectrodes.Withtheirhighenergydensityandlowcostrelativetothatofconventionalsinterednickelelectrodes,pastednickelelectrodeshavenowbeenwidelyusedincommerciallyavailableNi/MHbatteries[1 ,2 ] .Asthedis charged stateactivematerialofthepastednickelelec trodes,thepropertyofsphericalnickelhydroxideisthekeytodeter… 相似文献
13.
WANG Chi-yu ZOU Jun FU Xin YANG Hua-yong 《浙江大学学报(A卷英文版)》2007,8(9):1422-1428
The characteristics of the fluidic flowmeter,which is a combination of impinged concave wall and bistable fluid amplifier,is investigated by experimental studies and numerical simulations. The numerical approaches are utilized to examine the time dependent flow field and pressure field inside the proposed flowmeter. The effect of varying structural parameters on flow characteristics of the proposed fluidic flowmeter is investigated by computational simulations for the optimization. Both the simulation and experimental results disclose that the hydrodynamic vibration,with the same intensity,frequency and 180° phase shift,occurs at axisymmetric points in the feedback channel of the fluidic flowmeter. Using the structural combination of impinged concave wall and bistable fluid amplifier and differential signal processing technique,a novel fluidic flowmeter with excellent immunity and improved sensibility is developed. 相似文献
14.
Many innovative teaching approaches lack classroom impact because teachers consider the proposals impractical. Making a teaching approach practical requires instrumentality (procedures), congruence (local fit), and affordable cost (limited time and resources).This paper concerns a study on the development and effects of a participatory design based teacher training trajectory aimed at making guided discovery learning (GDL) practical for student biology teachers. First, we identified practical heuristics for designing GDL lessons by analyzing design protocols made by biology teachers who are experts in GDL. Next we inventoried student responses to their regular lessons and to GDL based lessons. Based on this we prepared a teacher training program for eleven student biology teachers in which they applied the heuristics and stepwise extended their teaching repertoire in the direction of GDL. The participants’ design processes and resulting lesson plans were scored on both use of design heuristics and GDL characteristics. The participants were interviewed about their motivational beliefs before and after the program. Results showed that student teachers are able to design GDL lessons and used the heuristics to design GDL lessons. Their motivation for implementing GDL in their classroom had increased substantially. The paper concludes with a critical reflection on our method of participatory design and its applicability. 相似文献
15.
From supply-push mode to demand-pull mode, SCM systems will face four main points: (1) real time visibility that covers the whole supply chain, (2) agility for choice of supply and source, (3) response to diverse customer demands and short delivery deadlines, and (4) rapid occurrence of new products following the market trends and new designs. Component-based SCM has become a hot spot in research areas. A multi-layer framework is set up, including a database server layer, an application server layer, a kernel component layer and a user interface layer. Some function components are designed, which are optimal planning arithmetic components, controller components and evaluation indexes components, in order to suit both discrete and continuous manufacturing. This paper studies a three-dimensional SCM configuration method based on the types of enterprise, manufacturing and products, provides powerful tools for SCM system implementations, and adopts an object-oriented technology to construct component-based distributed information system to assure right time, right materials, right place, right quantity and right customers. 相似文献
16.
Jiesi Guo Herbert W. Marsh Philip D. Parker Theresa Dicke Oliver Lüdtke Thierno M. O. Diallo 《Structural equation modeling》2019,26(4):529-556
In this study, we contrast two competing approaches, not previously compared, that balance the rigor of CFA/SEM with the flexibility to fit realistically complex data. Exploratory SEM (ESEM) is claimed to provide an optimal compromise between EFA and CFA/SEM. Alternatively, a family of three Bayesian SEMs (BSEMs) replace fixed-zero estimates with informative, small-variance priors for different subsets of parameters: cross-loadings (CL), residual covariances (RC), or CLs and RCs (CLRC). In Study 1, using three simulation studies, results showed that (1) BSEM-CL performed more closely to ESEM; (2) BSEM-CLRC did not provide more accurate model estimation compared with BSEM-CL; (3) BSEM-RC provided unstable estimation; and (4) different specifications of targeted values in ESEM and informative priors in BSEM have significant impacts on model estimation. The real data analysis (Study 2) showed that the differences in estimation between different models were largely consistent with those in Study1 but somewhat smaller. 相似文献
17.
Visualising subsurface processes in hydrogeology and building intuition for how these processes are controlled by changes in forcing is hard for many undergraduate students. While numerical modelling is one way to help undergraduate students explore outcomes of multiple scenarios, many codes are not user‐friendly with respect to defining domains, boundary conditions, and coupling processes, and numerical modelling exercises are also often disconnected from systems that the students understand, limiting their ability to extrapolate what they have learned for other situations. Here, we test the hypothesis that hydrogeology students will better estimate rates of groundwater flow and contaminant transport and the magnitudes of the parameters that control flow and transport by linking physical and numerical models. We present an exercise that links physical and numerical modelling of fluid flow and solute transport using 2‐D ‘ant farm’ sand tanks with parallel models in COMSOL Multiphysics. The sand tank exercises provide students with a way to visualise subsurface flow and transport processes, while COMSOL allows them to explicitly pull apart the mathematics associated with these systems and build intuition for their solutions. Given coupled experimentation and numerical exercises, we find that students will connect processes that they see in the laboratory with the outcomes of numerical models, and the post‐exercise tests indicate that they have an improved understanding of: (1) the magnitude and importance of properties and parameters that control flow and transport and (2) the simplifications made in numerical models of physical systems. 相似文献
18.
考虑修正NLG(一种变模形式非线性Galerkin)方法求解二维Navier-Stokes方程的全离散形式，通过一个例子的数值实现，按几种不同形式作了计算，数值算例表明了在不损失精度的情况下，修正NLG方法于CPU耗时方面有明显的节省。 相似文献
19.
CHANSON Hubert 《浙江大学学报(A卷英文版)》2006,7(8):1396-1405
INTRODUCTION A hydraulic jump is the sudden transition from a high-velocity, supercritical open channel flow into a slow-moving, sub-critical flow (Belanger, 1840; Bakhmeteff, 1932; Henderson, 1966; Chanson, 2004a). It is characterised by a sudden rise of the free-surface, with some strong energy dissipation and mixing, large-scale turbulence, air entrainment, waves and spray (Fig.1). Early experimental studies of air bubble entrainment were conducted in terms of the quantity of entrain… 相似文献
20.
胡月莲 《温州职业技术学院学报》2006,6(4):36-38
微通道传热技术是近几年发展起来的一门新兴的传热技术,具有传热效率高、结构紧凑等优点,是当前流动与传热研究的重要课题。运用计算流体力学程序(CFX)对环形微通道内单相水的流动与换热进行数值模拟,可以形象地描述出管内的流场和温度场,从中分析各种因素对流动与换热所产生的影响。 相似文献