铝液在多孔介质中渗流过程的模拟试验研究

选择低压渗流法制备泡沫铝的工艺过程为模拟对象,根据相似原理,在有机玻璃模型中用液体作为流体,对铝液在多孔介质中的低压向上渗流过程进行了模拟试验研究。试验表明,在低压渗流制备泡沫铝的过程中,原型的渗流液面是以平面沿铅垂方向向上推进的,位移和时间的关系满足四次方根规律;渗流过程中某一时间t的雷诺数、阻力系数和沿程损失可用相应的公式计算;渗流过程中,外加渗流气压的最佳值为0.04kPa,高于该值的外加渗流气压对于渗流时间的影响不大。实验还将模拟实验得到的结果与原型进行了比较,模型的充填时间与原型的充填时间一致性良好,证实了本实验结果的正确性。     

液态铝低压渗流过程的模拟试验研究

根据相似原理对黏度不同的液态铝在多孔介质中的低压向上渗流过程进行了模拟试验研究。试验表明，渗流液面以平面沿铅垂方向推进，并满足次方根规律；某一时刻t的雷诺数、阻力系数和沿程损失可用相应的公式计算；液态铝的黏度在一定范围（5％）的变化对渗流速度的影响不大，模拟与原型的充填时间有良好的一致性。     

低渗透多孔介质中的非线性渗流理论

文中论述了低渗透性多孔介质中非线性渗流理论的几个问题,阐明了渗流流体的性质,指出了多孔介质对流体通过的选择性,提出了新的非线性渗流方程,用实验资料对其进行了验证,分析了该方程演变功能,表明它可以描述各种渗流规律.该方程的各项参数都可从实验中直接得到,应用方便,并且参数的物理意义明确.     

可变形多孔介质中的一维非定常耦合渗流

在Ｂｉｏｔ理论的基础上,考虑到可变形多孔介质的渗透系数依赖于孔隙变形的特点,建立了耦合渗流问题的基本方程;用初始层校正法求出了一维非定常耦合渗流问题的摄动解;实例计算表明,耦合分析与非耦合分析之间的判别较大,因此耦合效应不能忽略。     

泡沫铝制备过程中铝液渗流的模拟试验研究

根据相似原理对铝液在多孔介质中的低压向上渗流过程进行了模拟试验研究。试验表明:渗流液面以平面沿铅垂方向推进,并满足四次方根规律;某一时刻t的雷诺数、阻力系数和沿程损失可用相应的公式计算;外加渗流气压的最佳值为0.40at。实验还将模拟充填时间与原型充填时间进了对比,两者得到了良好的一致性。     

多孔介质非线性渗流问题的摄动解

考虑变形多孔介质渗透参数(渗透率和孔隙度)与孔隙压力呈负指数变化的特点，建立了多孔介质渗流问题的数学模型，采用积分变换方法求出了一维非线性渗流问题的摄动解，并对常数渗透参数和指数渗透参数的渗流问题进行对比分析，计算结果表明：两者之间的差别较大，且渗透参数的变化对于流体渗流中后期过程有着重要的影响，但对渗流早期影响不大，这对于定量研究工程中非线性渗流问题模型参数的相对重要性提供了可靠的理论依据。     

幂律流体在多孔介质中径向渗流的分形模型

基于分形理论及毛细管模型,本文研究了非牛顿幂律流体在各向同性多孔介质中径向流动问题,推导了幂律流体径向有效渗透率的分形解析表达式．研究结果表明,幂律流体径向有效无量纲渗透率模型和Chang and Yortsos’s模型吻合很好;同时还得出幂律流体径向有效渗透率随孔隙率、幂指数的增加而增加,随迂曲度分形维数的增加而减少．     

非饱和多孔介质中热-渗流-力学耦合的混合元法

提出了一个非饱和多孔介质中热-渗流-力学耦合分析的混合有限元 方法. 固相位移、应变和净应力；孔隙水和气的压力、压力空间梯度和Darcy速度；多相混 合介质的温度、温度空间梯度和热流量在单元内均为独立变量分别插值. 基于胡海 昌-Washizu 三变量广义变分原理给出的多孔介质中热-渗流-力学耦合问题控制方程的单元弱形式，导 出了单元公式. 采用共旋公式进行几何非线性分析. 数值结果证明了所提出的单元模拟以 应变局部化为特征的渐进破坏的能力     

孤立波与多孔介质结构物的非线性相互作用

基于精确至Ｏ（εμ＾２,μ＾４）的多孔介质无压渗流模型方程和均匀流体质波动的Ｂｏｕｓｓｉｎｅｓｑ方程,本文对孤立波与多孔介质结构物的相互作用了较系统的数值实验。控制方程采用基于有限差分方程离散,在时域上采用了预估－校正方法进行了时间积分。在求解演化方程的过程中,引入“内迭代”过程实现流体域和多孔介质交界面的连接条件。结果表明孤立波在多孔介质上的反射与在不可渗透的界面上的反射类似,形成反向的孤立波但     

多孔泡沫铝压缩过程中微结构演化

本文采用SXR-CT技术研究金属多孔泡沫铝材料在压缩过程中内部微结构的演化。获得了泡沫铝试件的各个断层图像,以及各断层图像组装得到的三维结构图像,由此计算得到不同断层的孔隙率和压缩时各断层的位移量。并给出一系列相同位置、不同压缩量状态下垂直截面图像,通过这些图像可以直接地观察压缩过程中泡沫铝内部微结构的演化。这些研究结果将为泡沫铝制备工艺的改进和材料与结构的优化设计提供有益的参考,并为泡沫铝压缩破坏机理的构建提供科学依据。其中SXR-CT技术重建图像的分辨率约为10.9μm。     

镁液和铝液的真空低压铸造过程的模拟试验研究

本文利用真空低压铸造工艺来制备镁合金和铝合金试样,选择该铸造工艺过程为模拟对象,根据相似原理,在有机玻璃模型中用液体作为流体,对金属镁液和铝液的真窄低压铸造过程进行了模拟试验研究.试验表明,在利用真空低压铸造工艺来制备镁合金和铝合金试样的过程中,原型的渗流液面是以平面沿铅垂方向向上推进的,位移和时间的关系满足四次方根规...     

Infiltration of Liquid Metals in Porous Compacts: Modeling of Permeabilities During Reactive Melt Infiltration

Reactive infiltration is a fast and cost-effective technique for manufacturing ceramic-matrix composites (CMCs). CMCs are used in elevated temperature applications like rocket engine casings, jet nozzles, gas turbine blades and nuclear cladding. There is an urgent need for minimizing experimental costs as well as optimizing process parameters during manufacture, so that we have minimized manufacturing costs and reduced infiltration times. Towards this end, the objective of this research was to develop an integrated micro-macro model of reactive flow of molten silicon in a porous preform consisting of carbon-coated silicon carbide fibers and then optimize process parameters computationally. The overall objective of the research was to arrive at a modified equation of Darcy's law for flow through a porous medium with the help of numerical/computational modeling. This paper deals with the flow of silicon through porous carbon at the macro level. The macro flow of silicon was integrated with an available micro model by determining the transient porosity from the micro model and using it in Darcy's law written for the macro flow of silicon. From the results of this study, we recommend suitable process parameters such as initial temperature of the solid reactant and the specific kind of reactants to be used for achieving complete infiltration. These conclusions are drawn after observation of the rate of decrease of permeability with more reaction.     

Experimental Study of Nonlinear Flow in Micropores Under Low Pressure Gradient

As throat radius decrease to micro-nanoscale, seepage in unconventional reservoirs such as ultra-low permeability and tight reservoirs differs from conventional ones. Flow experiment in micropores is a promising approach to study characteristics of microflow. In this paper, a visual experimental device was established. Water flow through micropores with radius of 1.38–10.03 \(\upmu \hbox {m}\) was investigated, under 0.033–16 MPa/m. The results showed that in microscale, water flow did not agree with Poiseuille equation. Flow rate was lower than theoretical value and showed nonlinear characteristics. In the near wall area, due to the attraction of solid wall, a stagnant fluid layer was formed. It occupied flow space and thus lowered flow rate. Its thickness declined with pressure gradient increasing, which led to nonlinear flow characteristics. When the pressure gradient was very high, the thickness stopped declining and kept constant. Afterward, the flow transited to linear. In pores with smaller radius, the steady stagnant layer was thinner, but took a larger proportion of the flow space. For tubes of \(r = 1.38, 4.81, 10.03\,\upmu \hbox {m}\), the thickness of steady stagnant layer was 0.11, 0.23, 0.27 \(\upmu \hbox {m}\), respectively.     

线性高温壁面多孔介质传热研究

以多孔介质为研究对象,采用整场求解法分析了多孔介质温度场和流场随Ra数的变化.研究结果表明:随着Ra增加,由开始流线均匀分布为一个顺时针大窝,逐渐变化为一个顺时针大窝,一个逆时针小窝;流线出现分叉现象;流线分布在两个窝中间和外侧,即流场在小窝中间剧烈流动而在大窝中央基本上保持静止状态;当Ra很小时,热的传输主要依靠传导作用,随着Ra数逐渐增大,对流作用成为热传输的主要动力;当Ra数小于105时,高温壁面Nu数基本在-110～-17间变化,最大值发生在底部,最大值为17,最小值发生在上部,最小值为-110.     

多孔介质中流动参数的三维显示

本文利用当今三维图形工作站提供的最新视觉化技术，动态显示多孔介质中流动的原理和方法，主要探讨三个问题：（１）改进参数场图像化的质量。力求以逼真的，生活化的三维图形显示参数场的分布；（２）尽可能加快动态显示速度，力求以更强的动感显示出流动过程中参数场的变化规律；（３）尽可能丰富图形编辑功能，提高人机联作交互性。     

砼受压全过程损伤的实验研究

本文利用ＭＴＳ公司８１５．０２型电液伺服实验系统对砼进行了等应变速率和单调和循环复受试验，测定了砼单调受压全过程的声发射特性和反复受压时砼弹性模量的变化，经研究发现与声光射相应的损伤能相对比和弹性模量的衰减比均可以表征砼的损伤发展程度，且具有较好的一致性，文中还根据试验结果，给出所定义损伤随应变变化的关系表达式。     

Numerical Simulation of Single-Phase and Multiphase Non-Darcy Flow in Porous and Fractured Reservoirs

A numerical method as well as a theoretical study of non-Darcy fluid flow through porous and fractured reservoirs is described. The non-Darcy behavior is handled in a three-dimensional, multiphase flow reservoir simulator, while the model formulation incorporates the Forchheimer equation for describing single-phase or multiphase non-Darcy flow and displacement. The non-Darcy flow through a fractured reservoir is handled using a general dual-continuum approach. The numerical scheme has been verified by comparing its results against those of analytical methods. Numerical solutions are used to obtain some insight into the physics of non-Darcy flow and displacement in reservoirs. In addition, several type curves are provided for well-test analyses of non-Darcy flow to demonstrate a methodology for modeling this type of flow in porous and fractured rocks, including flow in petroleum and geothermal reservoirs.     

Study of Heat Transport in a Porous Medium Under G-jitter and Internal Heating Effects

In this article we study the combined effect of internal heating and time-periodic gravity modulation on thermal instability in a closely packed anisotropic porous medium, heated from below and cooled from above. The time-periodic gravity modulation, considered in this problem can be realized by vertically oscillating the porous medium. A weak non-linear stability analysis has been performed by using power series expansion in terms of the amplitude of gravity modulation, which is assumed to be small. The Nusselt number has been obtained in terms of the amplitude of convection which is governed by the non-autonomous Ginzburg?CLandau equation derived for the stationary mode of convection. The effects of various parameters such as; internal Rayleigh number, amplitude and frequency of gravity modulation, thermo-mechanical anisotropies, and Vadász number on heat transport has been analyzed. It is found that the response of the convective system to the internal Rayleigh number is destabilizing. Further it is found that the heat transport can also be controlled by suitably adjusting the external parameters of the system.