共查询到16条相似文献,搜索用时 402 毫秒
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根据多孔介质微观结构的分形尺度标度特征,采用蒙特卡罗方法分别重构随机多孔介质的微观颗粒和孔隙结构,并基于分形毛管束模型研究多尺度多孔介质的气体渗流特性,建立多孔介质微观结构和宏观渗流特性的定量关系。结果表明:分形蒙特卡罗重构的多孔介质微细结构接近真实介质结构,气体渗流特性的计算结果与格子玻尔兹曼模拟数据较为吻合; 多孔介质气体渗透率随着克努森数的增加而增大,孔隙分形维数对于气体渗流的微尺度效应具有显著影响,而迂曲度分形维数对于表观渗透率和固有渗透率的比值影响可以忽略。提出的分形蒙特卡罗方法具有收敛速度快且计算误差与维数无关的优点,有利于深入理解多尺度多孔介质的渗流机理。 相似文献
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用Lattice Boltzmann方法确定多孔介质的渗透率 总被引:8,自引:1,他引:7
应用7-Bit的正六角形格子的不可压缩Lattice Boltzmann模型,对多孔介质中的流动进行模拟,通过研究流量和压力梯度的关系,给出了Lattice Boltzmann方法模拟的Darcy定律。调节孔隙率,粘性系数等参数,给出了渗透率与这些参数的关系曲线。 相似文献
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研究了弹性波在非均匀裂纹孔隙介质中的传播特性,建立了各向异性喷射流模型.当弹性波通过裂纹孔隙介质时,由于波的扰动及裂纹和孔隙几何结构的不一致,导致在裂纹内部及裂纹与周边孔隙之间同时存在着流体压力梯度.此时的弹性波波动响应中包含着裂纹内连通性特征和背景孔隙渗透率信息.流体的动态流动过程使得介质的等效弹性参数为复数(非完全弹性),并且具有频率依赖性.当弹性波为低频和高频极限时,介质为完全弹性;当处于中间频段时,波有衰减和频率依赖.裂纹孔隙介质的各向异性连通性(渗透率)对应着各向异性特征频率(当渗流长度等于非均匀尺度时的弹性波频率),波的传播受到裂纹内连通性的影响.在一定频段内,随着裂纹厚度的增加,将出现第二峰值,峰值大小同时受到裂纹厚度和半径的影响. 相似文献
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对熔融盐高温斜温层蓄热过程进行了较深入的理论与实验研究.基于多孔介质局部热平衡理论,建立了多孔介质中熔融盐流体斜温层蓄热的局部热平衡数值模型,研究了熔融盐、多孔介质孔隙结构参数对多孔介质中熔融盐流体传热与流动的影响规律,并在熔融盐传热-蓄热实验平台上进行了试验研究.结果表明:与熔融盐单相流体斜温层(无填充多孔介质)蓄热系统相比,多孔介质填料能够减少斜温层的厚度和改善其形状,采用单位体积热容量(pc)s大于(pc)f,孔隙率(?)小于0.4有利于降低斜温层厚度及其移动速度.揭示了多孔介质中熔融盐流体斜温层蓄热系统的蓄热特性,为熔融盐高温斜温层蓄热的设计和运行控制提供依据. 相似文献
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温室内多孔蓄热墙传热与流动特性 总被引:1,自引:0,他引:1
本文采用一维稳态饱和多孔介质能量双方程模型,对温室内多孔蓄热墙的传热与流动特性进行了研究.结果表明:多孔蓄热墙的固体骨架与空气之间的换热取决于空气的入口流速、多孔材料的孔隙率、渗透率和固体骨架的导热系数,由于多孔蓄热墙接受的太阳辐照是不均匀的,因此推荐采用具有不同孔隙率的新型复合多孔蓄热墙,以减少这种不利的影响. 相似文献
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An analysis of the radial flow in the heterogeneous porous media based on fractal and constructal tree networks 总被引:1,自引:0,他引:1
In this paper, an analysis of the radial flow in the heterogeneous porous media based on fractal and constructal tree networks is presented. A dual-domain model is applied to simulate the heterogeneous porous media embedded with a constructal tree network based on the fractal distribution of pore space and tortuosity nature of flow paths. The analytical expressions for seepage velocity, pressure drop, local and global permeability of the network and binary system are derived, and the transport properties for the optimal branching structure are discussed. Notable is that the global permeability (Kn) of the network and the volume fraction (fn) occupied by the network exhibit linear scaling law with the fractal dimension (Dp) of channel diameter bylogKn∼0.46Dp and logfn∼1.03Dp, respectively. Our analytical results are in good agreement with the available numerical results for steady-state soil vapor extraction and indicate that the fractal dimension for pore space has significant effect on the permeable properties of the media. The proposed dual-domain model may capture the characteristics of heterogeneous porous media and help understanding the transport mechanisms of the radial flow in the media. 相似文献
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A particle model for resistance of flow in isotropic porous media is developed based on the fractal geometry theory and on the drag force flowing around sphere. The proposed model is expressed as a function of porosity, fluid property, particle size, fluid velocity (or Reynolds number) and fractal characters D f of particles in porous media. The model predictions are in good agreement with the experimental data. The validity of the proposed model is thus verified. 相似文献
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In this study, the effects of variable fluid properties on heat transfer in MHD Casson fluid melts over a moving surface in a porous medium in the presence of the radiation are examined. The relevant similarity transformations are used to reduce the governing equations into a system of highly nonlinear ordinary differential equations and those are then solved numerically using the Runge–Kutta–Fehlbergmethod. The effects of different controlling parameters, namely, the Casson parameter,melting and radiation parameters, Prandtl number,magnetic field, porosity, viscosity and the thermal conductivity parameters on flow and heat transfer are investigated. The numerical results for the dimensionless velocity and temperature as well as friction factor and reducedNusselt number are presented graphically and discussed. It is found that the rate of heat transfer increases as the Casson parameter increases. 相似文献
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多孔介质热导率的数值计算 总被引:2,自引:0,他引:2
通过数值模拟得出面积分形维数和孔隙率相同,而孔隙结构不同的分形多孔介质的导热特性是不相同的.说明仅仅依靠孔隙率和分形维数两个参数无法有效确定多孔介质的热物理性质,寻找新的表征孔隙结构的参数是必要的.同时也说明了前人所得出的关于多孔介质的热物性的解析表达式具有一定的局限性和不确定性. 相似文献
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In this Letter, a difference-fractal model for the permeability of viscous flow through fibrous porous media is proposed. Since fractal objects have well-defined geometric properties, and are discrete and discontinuous, we apply the difference approach to developing the fractal model. The model of non-dimensional permeability is expressed as a function of porosity and fractal dimension. To verify the validity of the proposed model, the predicted permeability values are compared with those of experimental measurements. A good agreement between the prediction of the fractal model and the existing experimental data from the literature is found. 相似文献
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A volume averaging approach is used to estimate the porous media permeability. Contrary to traditional methods that rely on solving the Navier-Stokes equations for laminar flow, this approach has the advantage that it does not require the specification of some physical conditions and parameters (pressure drop and viscosity). Numerical results on synthetic models of porous media showed that (i) the local porous medium configuration has an important effect on the permeability value, and (ii) the Carman-Kozeny equation cannot describe the permeability behavior as a function of porosity and characteristic lengths. In turn, our results indicate that simple empirical equations, commonly used in practice, are unable to describe the permeability functionalities over a broad range of porous media configurations. 相似文献