致密破碎多孔介质渗透率测量方法

基于均匀各向同性多孔介质、达西渗流和理想气体假设,考虑Klinkenberg效应建立了针对具有纳米尺度孔径的低渗透率多孔介质中的渗流模型。针对致密球形破碎样品的压力脉冲实验,建立了相应的边界条件,同时利用有限差分方法获得其实验腔的压力变化曲线的数值解。通过对渗流方程进行量纲1化,引入了与孔隙率、渗透率和滑移参数有关的量纲1参数Z、Z^*和b_K。通过改变参数Z、Z^*和b_K研究了样品边界处压力的变化规律,给出了一种数据处理方法,对于致密球形破碎多孔介质的压力脉冲实验,通过对实验测量的样品边界处压力曲线的分析,结合偏微分方程正问题的数值解,可以确定样品的孔隙率、渗透率和滑移参数,从而更为简便地分析压力脉冲衰减曲线实验数据,得到致密多孔介质样品渗透率。     

臭氧催化氧化反应器模拟与分析

臭氧催化氧化法是一种高效的污水处理技术,是目前污水高级处理的主要手段之一。传统的建模方法无法研究反应器内污水浓度的时空分布和操作条件对反应器的影响,本研究利用计算流体力学（CFD）,耦合多孔介质流动与传质和化学反应动力学多物理场模型,研究臭氧催化氧化过程中目标污染物浓度随时间和空间的分布情况,计算结果与实验结果有良好的一致性。进一步研究臭氧浓度和流量、循环水流量、催化剂层高度、催化剂颗粒大小等对臭氧催化氧化处理废水效率的影响,评估出最优的实验方案。结果表明,在不改变当前反应器主体结构的情况下,最优的操作条件是：臭氧浓度30～40mg/L,臭氧进口流量40～60mL/min,循环水量200～250mL/min,催化剂层填充高度600～800mm,催化剂颗粒半径大小为2mm。该研究有助于理解、设计和优化污水处理反应器。     

致密破碎多孔介质渗透率测量方法

基于均匀各向同性多孔介质、达西渗流和理想气体假设,考虑Klinkenberg效应建立了针对具有纳米尺度孔径的低渗透率多孔介质中的渗流模型。针对致密球形破碎样品的压力脉冲实验,建立了相应的边界条件,同时利用有限差分方法获得其实验腔的压力变化曲线的数值解。通过对渗流方程进行量纲1化,引入了与孔隙率、渗透率和滑移参数有关的量纲1参数Z、Z*和bK。通过改变参数Z、Z*和bK研究了样品边界处压力的变化规律,给出了一种数据处理方法,对于致密球形破碎多孔介质的压力脉冲实验,通过对实验测量的样品边界处压力曲线的分析,结合偏微分方程正问题的数值解,可以确定样品的孔隙率、渗透率和滑移参数,从而更为简便地分析压力脉冲衰减曲线实验数据,得到致密多孔介质样品渗透率。     

升温条件下多孔介质内气泡的生长和聚并行为

设计了两种横向和纵向喉道宽度比值(w_h∶w_z)分别为1.48∶1和1∶1的各向异性和各向同性多孔介质微流体芯片,以CO₂为气体,二甲基硅油为液体,采用可视化实验,系统地研究了升温条件下多孔介质结构对气泡生长和聚并规律的影响。结果表明,温度升高引起的传质生长是气泡突破喉道的动力。单个气泡在多孔介质内生长方向的选择依赖于喉道的门阙压力,气泡倾向于突破门阙压力小的喉道。随着温度的升高,气泡侵入和突破喉道速度加快。在各向异性多孔介质中,气泡倾向于在横向生长时与其他气泡发生聚并,而在各向同性多孔介质中,气泡更易发生纵向聚并。当多个气泡存在于各向异性多孔介质内时,气泡的初始分布会显著影响气泡间的生长和聚并过程;在各向同性多孔介质内时,影响则较小。各向异性多孔介质在实际工程应用过程中更易实现气泡流型调控。     

多孔介质燃烧-换热器的二维数值研究

通过二维数值模型研究了多孔介质燃烧-换热器。在宽广的工况范围内,研究多孔介质燃烧-换热器内的温度、速度分布和压力损失,研究主要工作参数过量空气系数和功率对换热管总的热效率的影响。结果表明,过量空气系数和功率对总的热效率有显著的影响,随二者的增大,总的热效率降低。实验验证了数值计算结果的有效性。     

热压工艺密实过程数值模拟

本文针对热压成型工艺,利用多孔介质有效应力原理和体积平均方法,建立了三维流动-热-化学耦合的数值模型.该模型将密实过程中的纤维层视为可变形的多孔介质,从而能反映纤维层变形的影响.在此基础上,本文采用有限元方法,结合ALE移动网格方法处理动边界,对热压工艺密实过程进行了数值分析.计算结果表明,与非耦合的经典模型相比,该模型给出的结果与实验吻合得更好.     

泡沫陶瓷内分形模型建立和燃烧数值分析

多孔介质（泡沫陶瓷）预混燃烧是一项新颖、独特的燃烧技术。本文将分形理论应用到多孔介质压降模型中,建立了分形模型。并且求解了多孔介质特性参数：粘性阻力系数与内部阻力系数。并针对实验条件进行燃烧数值模拟研究。通过和实验数据对比,发现数值模拟和实验能较好相符合,说明此模型具有一定的可靠性。     

泡沫液在均质多孔介质内动态驱替过程的二维数值模拟研究

利用随机泡沫数目守恒模型,针对具有收缩进口及收缩出口的均质多孔介质二维模型,对泡沫流体驱替突破前的动态过程开展了数值模拟研究。采用IMPES方法对二维两相泡沫动态驱替过程的控制方程组进行求解,通过液相压力、液相饱和度、气泡数目等参数在多孔介质内的分布结果对泡沫动态驱替特性进行了分析研究。数值模拟结果表明,泡沫驱替过程显示出明显的入口效应,其压力分布、液相饱和度及泡沫数目分布随气体与活化剂溶液在缩小入口的注入呈现明显的发展过程。在泡沫液未完成驱替突破的情况下,缩小出口未显示出对泡沫液驱替特性的影响。数值计算结果与相应实验结果趋势一致,表明所采用的随机泡沫数目守恒模型能够正确表征多孔介质中泡沫的生成及湮灭机理,进而对泡沫液在均质多孔介质内的动态驱替特性进行准确模拟和预测。     

两种毛管压力模型对比的储层孔隙结构分形研究

基于多孔介质分形理论进行Li-Horne毛管压力模型和Brooks-Corey毛管压力模型的推导,证明Brooks-Corey毛管压力模型为Li-Horne毛管压力模型的一种特殊形式。并利用两种毛管压力模型对北部湾盆地不同渗透率岩样的压汞曲线进行拟合,获得孔隙大小分布指数来评价储层的非均质程度,由于Brooks-Corey模型适用于均质储层,而Li-Horne模型对于均质、非均质储层均适用,所以Li-Horne模型拟合结果好于Brooks-Corey模型。同时,根据Li-Horne模型推导出多孔介质孔隙分布的分形概率模型,其指数与分形维数有关,利用该模型计算的孔喉尺寸分布与压汞曲线获得的结果一致。     

泡沫液在均质多孔介质内动态驱替过程的二维数值模拟研究

利用随机泡沫数目守恒模型,针对具有收缩进口及收缩出口的均质多孔介质二维模型,对泡沫流体驱替突破前的动态过程开展了数值模拟研究。采用IMPES方法对二维两相泡沫动态驱替过程的控制方程组进行求解,通过液相压力、液相饱和度、气泡数目等参数在多孔介质内的分布结果对泡沫动态驱替特性进行了分析研究。数值模拟结果表明,泡沫驱替过程显示出明显的入口效应,其压力分布、液相饱和度及泡沫数目分布随气体与活化剂溶液在缩小入口的注入呈现明显的发展过程。在泡沫液未完成驱替突破的情况下,缩小出口未显示出对泡沫液驱替特性的影响。数值计算结果与相应实验结果趋势一致,表明所采用的随机泡沫数目守恒模型能够正确表征多孔介质中泡沫的生成及湮灭机理,进而对泡沫液在均质多孔介质内的动态驱替特性进行准确模拟和预测。     

ANALYSIS OF PERMEABILITY FOR ELLIS FLUID FLOW IN FRACTAL POROUS MEDIA

This work studies the flow characteristics of Ellis fluid in saturated porous media. A fractal model is developed for the effective permeability of Ellis fluid flow in porous media based on the assumptions that porous media consist of a bundle of tortuous capillaries, whose size distribution and tortuosity follow the fractal scaling laws. The average flow velocity and the effective permeability for Ellis fluid flow in porous media are derived. The proposed fractal model does not contain any empirical constant, and every parameter in the model has clear physical meaning. The model predictions are compared with the measured data, and good agreement between them is obtained.     

Some aspects of wetting/dewetting of a porous medium

Various features of wetting/dewetting of porous media are examined. The phenomenon of capillary hysteresis is illustrated by a vertical capillary tube which consists of an alternating sequence of convergent—divergent conical sections. A study of the kinetics of wetting of this tube by a liquid shows that when the velocity of the liquid/vapour meniscus is plotted against the height of penetration, it oscillates about the Washburn velocity—distance curve and performs Haines jumps. A general macroscopic equation is derived for the rate of wetting/dewetting of a porous medium having randomly distributed, finely divided particles or pores. Use is made of the Forchheimer equation, which is an extension of Darcy's equation to higher Reynolds numbers. Dissipative energy terms due to internal fluid calculaton and to irreversible movements of the meniscus strongly affect the initial rate of imbibition, but as the wetting progresses the Reynolds number decreases and Washburn's equation prevails.The application of percolation theory to wetting/dewetting phenomena in porous media is studied. The use of percolation theory by Kirkpatrick and Stinchcombe to find the electrical conductivity of inhomogeneous solid mixtures is adapted to determining the permeability of a porous medium to fluid flow. It is also shown how the relation between the “precolation probability” and the concentration of “unblocked” channels or pores can be applied in calculating the capillary pressure—desaturation curve in drainage. In particular, percolation theory predicts that a threshold pressure or break-through pressure is required before a non-wetting fluid can displace a wetting fluid in a porous medium. It is often convenient to use tree-like or branching lattice networks as models of a porous medium, because these are amenable to exact solutions in regard to percolation probability and permeability. The percolation properties of porous medium models which consist of lattice networks of cylindrical channels with a distribution of cross-sections and also of randomly packed rotund particles are examined and their relevance to wetting/dewetting phenomena discussed.     

山谷型双流程凝汽器管侧流场的数值分析

为提高凝汽器换热效率,应用Fluent6.3数值模拟软件,管束区域采用多孔介质模型,对山谷型双流程凝汽器水室流场进行了数值分析。研究结果表明:该凝汽器入口水室结构存在一定的缺陷,导致冷却水在水室顶部和管板两处产生较大的局部阻力,从而产生了两处较大漩涡,影响设备的安全和稳定性;后水室流场较为均匀,漩涡较小,结构比较合理;出口水室前后侧速度较大,中间部位存在较大的低速区域,同时在右侧壁面出现了高速区域,从而会对右侧壁面造成较大的冲击力和摩擦力。     

Pressure drop modelling in cellular metallic foams

A theoretical model is presented for the prediction of pressure drop in a Newtonian fluid flowing through highly porous, isotropic metallic foams. The model is based on a rigorous assumption of piece-wise plane Poiseuille flow and a simplistic geometrical model, and shows promise to accurately predict the hydrodynamic conditions in both the Darcy and Forchheimer regimes, without a priori knowledge of the flow behaviour of the particular metallic foam.     

高温金属熔液在旋转多孔介质内的渗流传热过程

针对转动坐标系中铝熔液在SiC多孔介质内的流动传热现象 ,考虑离心力对渗流传热过程的影响 ,采用局部非热平衡假设建立多孔介质渗流传热数理模型 ,研究不同工况下流体的流速、压力损失及铝熔液和多孔介质的温度变化 .计算结果表明 :在渗透区域 ,液固两相存在温差 ,且液固温差随渗透界面的移动而减小 ;在非渗透区域 ,固体的温度曲线基本不变 .离心转速或孔隙率的增加都使渗透前沿区域液固两相温差增大 .孔隙率对流场和压力损失有较大影响.     

Supercritical fluid flow in porous media: modeling and simulation

The present work aims the modeling and simulation of supercritical fluid flow through porous media. This type of flow appears in several situations of interest in applied science and engineering, as the supercritical flow in porous materials employed in chromatography, supercritical extraction and petroleum reservoirs. The fluid is constituted of one pure substance, the flow is monophasic, highly compressible and isothermal. The porous media is isotropic, possibly heterogeneous, with rectangular format and the flow is two-dimensional. The heterogeneities of porous media are modeled by a simple power law, which describes the relationship between permeability and porosity. The modeling of the hydrodynamic phenomena incorporates the Darcy's law and the equation of mass conservation. Appropriated correlations are used to model, in a realistic form, the density and the viscosity of the fluid. A conservative finite-difference scheme is used in the discretization of the differential equations. The nonlinearity is treated by Newton method, together with the conjugate gradient method. The results of the simulation for pressure and mobility of supercritical and liquid propane flowing through porous media are presented, analyzed and graphically depicted.     

增强反应注射成型机混合头内流体高压高速对撞过程模拟与分析

以型号为MK?8/12UL?2K的L 形混合头为模型，运用了CFD数值模拟软件对混合头腔内两相物料流体的高压高速对撞进行了模拟分析。通过控制变量法分别探究了流量和黏度对混合结果的影响，同时为了更好地表征玻璃微珠在混合过程中的运动情况，还对整个流场进行了粒子示踪分析。结果表明，增加质量流量会导致混合腔内速度压力的提升，也就是对撞程度变高，对撞的位置会更加偏向于黏度高的物料出口侧；增加黏度会导致混合腔内物料的压力提升速度降低，同时对撞的位置会明显更加偏向于黏度高的物料出口侧，且摩擦力显著增加；粒子停留时间则随质量流量的提高而减短，随物料黏度的提高而增加；通过模拟获得的这些结果为混合头设计及工艺优化工作提供了一定的参考价值。     

Non-Newtonian purely viscous flow through isotropic granular porous media

An analytical model for predicting non-Newtonian purely viscous power law flow through isotropic granular porous media is proposed. Application of the method of volume averaging leads to macroscopic momentum transport equations describing the physical flow phenomena within the porous medium. The geometrical properties of the granular porous medium are incorporated through the introduction of a rectangular representative unit cell model. The relative positioning of neighbouring cells leads to staggered- and non-staggered arrays of solid constituents. Volume partitioning of the flow domain allows for the tortuosity to be expressed as a ratio of fluid volumes. In order to support the assumption of average geometrical isotropy of the unit cell model, a weighted average is performed over the different arrays. The coefficient obtained from the averaging procedure is based purely on physical principles. Through application of an asymptotic matching technique, the proposed model produces pressure gradient predictions for Reynolds numbers within the entire laminar flow regime. The analytical model is compared to published experimental data to verify the validity of the model.     

并流多通道管壳式换热器壳侧流场数值研究

采用多孔介质-分布阻力模型,对一种新型并流多通道进出口结构(MPC)轴流管壳式换热器壳程流场进行数值研究.在传热管长6.0 m不变,分别针对长径比L/D=2.0和L/D=1.5二种情况,研究Re和通道数N对壳侧流场的分布及阻力变化规律.结果表明:在相同的Re和L/D下,随着N的增加,壳程的流场分布不均现象得到有效的遏制...