生化过程的非结构模型和结构模型

本文介绍了生化过程的两类主要的数学模型——非结构模型和结构模型的结构和建模方法。并在分析两者特点的同时。提出了今后有关这类过程模型化的对策之设想。     

对化学教学中“模型认知”的认识与思考

模型认知是高中化学课程标准的核心素养之一。当前在中学化学学科领域内,关于模型及建模的研究主要集中在模型认知视角下的教学研究、建模教学在中学化学中的应用、中学化学复习课中模型的建构与应用研究等三个方面。模型的定义和化学模型的分类能帮助教师和学生更好地认识模型。模型定义的核心表达是为了某种特定的目的,利用简化、抽象、类比等方法,对事物的本质进行表征,将抽象思维外显化。化学认知模型和化学认识模型共同指导化学学科知识的学习,基于模型的教学策略是落实模型认知素养的重要途径之一。     

一种预测页岩气井产量递减的组合模型研究

页岩气井产量递减预测方法主要有数值模拟法、解析法和经验法三大类,其中经验法因为只需生产数据、操作简单且有效而被广泛使用。目前主要有SEPD模型、Duong模型和YM-SEPD模型等单一模型,鉴于页岩气藏压裂水平井复杂的流动机理和渗流规律,单一递减模型难以适应现场需要。在详细分析了目前适用于页岩气藏单井产量预测最常用的两种经验方法—SEPD和Duong模型的基础上,提出了以此为基础的产量递减经验法分析新组合模型,并以四川盆地页岩气井生产数据为例,分析对比了新方法与SEPD法和Duong法的预测结果,印证了新方法更具优势、预测更为准确。     

CAD/CAM系统的数据模型

对 CAD/ CAM系统的几种数据模型的原理和特点等进行了阐述和比较。线框模型、表面模型、实体模型这三种表示方法各有特色 ,特征造型的方法正越来越多地被人们所重视 ,成为新一代的造型技术     

页岩气吸附模型的研究进展

为了更好地拟合页岩气吸附实验,研究了经典的langmuir模型,发现其局限性。为了弥补langmuir模型的局限性,相继列举了数个页岩气吸附模型如EL模型、双langmuir模型、BET模型和D-R模型等,各个模型都有其优势与不足。我们需要根据特定的条件,选择合适的页岩气吸附模型才能更精准地拟合页岩气吸附实验。     

地理信息系统与环境模型集成的探讨

文章从地理信息系统与环境模型集成的必要性入手,对GIS与环境模型集成的方式、步骤等问题作了一些探讨,并指出了其未来的发展趋势.     

三元催化转化器数学模型的发展研究

介绍了三元催化转化器的结构及工作原理,论述了目前开发出的催化转化器的各种数学模型,包括温度模型,二维模型,多维模型,及动力学模型等。对今后催化转化器数学模型的研究方向做了展望。     

Petrel软件在油藏三维地质建模中的应用

油藏三维地质建模是油藏精细描述的核心,也是油藏数值模拟研究的基础。Petrel 软件是油藏三维地质建模中使用的主流软件,它通过对油藏的构造特征,属性特征进行模拟,建立符合油藏实际地质特征的三维可视化地质模型,指导剩余油挖潜和提高采收率。     

直饮水处理技术WBS模型分析及应用启示

文中介绍了美国环境保护署(EPA)的新成本建模方法,并应用于开发直饮水处理技术的单位成本.该技术使用工作分解结构(WBS)方法,将不同工艺拆分为分散的处理单元,以估计单位成本.演示了该模型在颗粒活性炭处理技术中的应用,并提供输出的示例,用于说明去除三氯乙烯活性炭处理技术的WBS技术模型.进一步以工程为例,应用WBS模型输出不同处理单元的成本分析,从经济角度分析优化工艺选择.最后提出对于该模型在我国工程领域的应用可能性及展望.     

三维建模在精细油藏描述中的应用研究

储层三维建模是精细油藏描述的核心,随着油田的开发和计算机水平发展,油藏的研究要求更高的定量化,储层的描述要求更加精细,建立精度较高的储层三维模型非常有意义。储层建模工作分为油藏构造建模,沉积微相建模和油藏属性建摸三步。文中讨论了这三种模型,并以靖安油田某区块为例说明了在油藏研究中的应用状况。     

CREEPING FLOW OF VISCOELASTIC FLUIDS THROUGH TAPERED SLIT DIES: AN ANALYTICAL SOLUTION

In the present study, it will be shown that at vanishingly small Reynolds numbers the extensional behavior of a fluid has a strong effect on its kinematics when flowing through a tapered slit die. To show this, the Cauchy equations of motion were simplified using the creeping flow approximation. Assuming the flow to be steady, laminar, two-dimensional, and incompressible, the governing PDEs were reduced to a set of coupled ODEs using a series solution in terms of the powers of 1/r. Two different constitutive equations, both incorporating an extensional parameter, were used in the analysis: (i) the Giesekus model and (ii) the Simplified Phan-Thien-Tanner (SPTT). An analytical solution was found for each fluid model clearly depicting the strong influence of the extensional parameter on the flow becoming non-radial within the channel.     

Modeling of the transient viscosity for polymer melts after startup of shearing and elongational deformations

In order to describe the transient stress growth for polymer melts, the empirical model proposed by Seo for the viscosity of steady‐state flow is combined with a phenomenological viscoelastic model of a differential type (the White–Metzner model) along the lines proposed by Souvaliotis and Beris. The relaxation time is taken as a function of the invariant of the stress tensor (hence that of the configuration tensor) rather than that of the rate of the deformation tensor. Numerical results show a good correlation with experimental data. The model predictions approach steady‐state values at long times after the startup. The nonlinear form of the model correlates very well with the experimental data over many decades of the deformation rate, both in shearing and elongational deformations. The proposed model is a simple one that can also describe the overshoot in the transient stress growth. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 510–515, 2003     

On the relative importance of the kinetic and frictional contributions to granular motion in an annular Couette flow

A quantitative assessment is made on the relative importance of the kinetic and frictional contributions to the motion of dry granular materials under shear in an annular Couette flow configuration. The assessment is based on comparing the modelling results using the kinetic-frictional model with the experiments. It is shown that the kinetic-theory-based model with equal weight of the collisional and frictional contributions, commonly used in the literature, gives a great deviation from the experimental results in the point of view of the dominant solids motion, while an increase in the weight of the frictional contribution improves the modelling towards the experimental results. An increase in the weight of the frictional contribution by 25-50% leads to the best match, suggesting the current constitutive relationship with equal weight of the kinetic and frictional contributions need to be refined in order to reflect the real dense granular flows.     

气提泵特性研究

研究了水、模拟料液、30%TRPO-煤油体系3种液体在高为6.2m气提泵中的气提特征,并用Parker一维模型对实验结果进行了分析和处理。详尽讨论了提升管管径、输送液体的粘度和表面张力对Parker模型中特征参数K、S的影响。     

基于段塞流的通用气液两相流模型的建立与验证

气液两相混输流动中,由于段塞流与其他流型均有联系,从段塞流出发建立模型可以使不同流型下的计算模型得到统一。基于段塞流建立气液两相流动量方程和连续性方程,完善模型对气泡和液滴夹带的处理。建立模型的闭合关系式,对关键参数(壁面及气液相间水力摩阻系数、液塞平移速度、平均液塞长度)的计算闭合关系式进行优选,得到适用于模型的闭合关系式,同时,对液滴和气泡的夹带给出夹带条件及相关参数计算式,最终建立基于段塞流的通用气液两相流模型。使用3组不同来源的实验数据验证了模型计算压降和持液率的准确性,实验数据分别来自中国石油大学(华东)、大庆油田实验基地的气液两相流实验以及国外研究人员的实验研究,包含各个气液流型。模型具有较高的计算精度,优于未经关系式完善和优化的原始模型,大部分压降及持液率参数的计算误差在±15%以内。     

气液固流化床流动介尺度模型研究进展

气液固流化床是一类重要的多相反应器,在化工及相关过程工业中有着广泛的应用。然而,由于对该类反应器内复杂的多相流动结构的定量描述十分有限,目前其设计和放大仍主要依赖经验,致使放大成功率低,反应结果达不到预期效果。因此,建立和完善气液固流化床内的三相流动机理模型,是实现该类反应器科学设计和放大的关键环节。对气液固流化床内的三相流动机理模型的研究进展进行了分析,着重总结了三相流动介尺度机理模型研究的新进展,并指出了存在的问题和进一步研究的方向,希望为该类反应器的基础研究和工业应用提供参考。     

基于行波法的段塞流瞬态捕捉模型建立与验证

气液两相流中,准确预测段塞流的特征参数具有重要的现实意义。Renault模型是基于非黏性Kelvin-Helmholtz（IKH）稳定性准则与黏性Kelvin-Helmholtz（VKH）稳定性准则建立的能够捕捉段塞前后界面运动的双流体模型,但该模型在液相单元格之间采用Riemann精确解,求解速度较慢。为简化计算,本文将行波法引入到Renault模型的液相方程求解过程,并对可能出现的干区用薄液膜代替,使行波法适用于所有计算单元,在保证模型精度的条件下,极大地提高了计算速度,运算时间相比Renault模型平均减少28%。对比本模型计算结果与室内小型环道实验数据,持液率与实测结果相一致,压降、段塞长度计算相对误差分别在25%、30%以内,且主要分布在20%以内。说明本文改进的瞬态段塞流模型具备运算快速、计算精度较高的特点,具有一定的工程应用价值。     

Simulation of a Spray Dryer Fitted with a Rotary Disk Atomizer Using a Three-Dimensional Computional Fluid Dynamic Model

Spray dryers fitted with a rotary disk atomizer are widely used in many industries requiring high throughputs to produce powders from liquid streams. The interaction between droplets or particles and the drying medium within the drying chamber is still not well understood and hence difficult to model reliably. In this article CFD results are presented to describe the behavior of the performance of a spray dryer fitted with a rotary disk atomizer in a cylinder-on-cone chamber geometry. Four different turbulence models, i.e., standard k - ε, RNG k - ε, Realizable k - ε, and Reynolds stress models were tested and compared to simulate the swirling two-phase flow with heat and mass transfer in the chamber. The results of this investigation can provide further insight into turbulent swirling flow modeling. The predicted results, such as, air flow patterns, air velocity and temperature, distributions, particle/droplet trajectories, drying performance etc., are obtained using the CFD code FLUENT6.1. Comparison with available limited experimental data shows that CFD results display reasonable agreement. Predicted results also show that the RNG k - ε model performs better in this specific case.     

Simulation of a Spray Dryer Fitted with a Rotary Disk Atomizer Using a Three-Dimensional Computional Fluid Dynamic Model

Abstract

Spray dryers fitted with a rotary disk atomizer are widely used in many industries requiring high throughputs to produce powders from liquid streams. The interaction between droplets or particles and the drying medium within the drying chamber is still not well understood and hence difficult to model reliably. In this article CFD results are presented to describe the behavior of the performance of a spray dryer fitted with a rotary disk atomizer in a cylinder-on-cone chamber geometry. Four different turbulence models, i.e., standard k ? ε, RNG k ? ε, Realizable k ? ε, and Reynolds stress models were tested and compared to simulate the swirling two-phase flow with heat and mass transfer in the chamber. The results of this investigation can provide further insight into turbulent swirling flow modeling. The predicted results, such as, air flow patterns, air velocity and temperature, distributions, particle/droplet trajectories, drying performance etc., are obtained using the CFD code FLUENT6.1. Comparison with available limited experimental data shows that CFD results display reasonable agreement. Predicted results also show that the RNG k ? ε model performs better in this specific case.