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多孔介质流的BDF2有限元解的误差分析
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作者 李瑜 张卓玥 蔡文涛 《杭州电子科技大学学报(自然科学版)》 2023年第4期50-56,共7页
提出多孔介质流方程的一种全离散有限元格式。在时间上采用2阶向后差分(Backward Differentiation Formula,BDF)有限元数值格式BDF2方法离散,空间上采用Galerkin-Galerkin有限元方法离散。由于非线性耦合项的存在,使得压力的有限元解的... 提出多孔介质流方程的一种全离散有限元格式。在时间上采用2阶向后差分(Backward Differentiation Formula,BDF)有限元数值格式BDF2方法离散,空间上采用Galerkin-Galerkin有限元方法离散。由于非线性耦合项的存在,使得压力的有限元解的低阶精度“污染”了浓度的有限元解的误差估计,引入一个拟椭圆投影“切断”压力有限元解和浓度有限元解的联系。对浓度项和压力项采用同阶的有限元空间进行离散,进一步分析得到关于浓度和压力的有限元解的无条件最优L^(∞)(0,T;L^(2))误差估计。 展开更多
关键词 不可压缩多孔介质流 BDF2 有限元方法 最优误差估计
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屏蔽电机内冷却循环流场及水力损失数值研究
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作者 郭苗 刘宇 +3 位作者 唐学林 刘树红 左志钢 李小芹 《水力发电学报》 CSCD 北大核心 2024年第10期53-62,共10页
本文采用RNG k-ε湍流模型对一屏蔽电机内部流动进行数值模拟,同时运用多孔介质模型及Ergun方程计算近似电机定子区域内流动,最终构建了基于能量守恒定律的水力损失分析理论模型,揭示了屏蔽电机内部水力损失演化过程,并结合相应流场现... 本文采用RNG k-ε湍流模型对一屏蔽电机内部流动进行数值模拟,同时运用多孔介质模型及Ergun方程计算近似电机定子区域内流动,最终构建了基于能量守恒定律的水力损失分析理论模型,揭示了屏蔽电机内部水力损失演化过程,并结合相应流场现象进行了分析。计算结果表明,转子与多孔介质两者间隙内流体成螺旋形流动,同时较大的多孔介质阻力将导致冲击水流在此间隙前出现多个轴对称漩涡;推力轴承径向流道间的进口处出现类似叶片绕流的轴对称漩涡,同时推力轴承外流场还存在强环流;研究结果揭示了复杂的几何结构会导致产生较多漩涡,且造成较大水力损失,尤其是在推力轴承与滑动轴承间。以上计算结果可为相似电机内部冷却循环流动开展相关几何参数和结构优化提供一定参考。 展开更多
关键词 多孔介质流 水力损失 漩涡 推力轴承 屏蔽电机
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地下岩体内多孔介质中裂隙流运移过程的COMSOL Multiphysics仿真模拟 被引量:4
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作者 柳崎 索丽敏 《系统仿真技术》 2019年第3期184-187,197,共5页
采用达西定律模拟多孔介质中裂隙流的实验,并利用时间函数定义进出口裂隙的压力以及流速。运用COMSOL Multiphysics 软件的地下流体多孔介质物理场,模拟岩心储水模型中流体的压力分布、范围、大小以及运移方向等,然后通过动画的形式展... 采用达西定律模拟多孔介质中裂隙流的实验,并利用时间函数定义进出口裂隙的压力以及流速。运用COMSOL Multiphysics 软件的地下流体多孔介质物理场,模拟岩心储水模型中流体的压力分布、范围、大小以及运移方向等,然后通过动画的形式展现。运用 COMSOL Multiphysics 软件来模拟裂隙流实验可以更加直观地观测到实验现象。 展开更多
关键词 COMSOL MULTIPHYSICS 裂隙 多孔介质流 实验教学
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基于多孔介质材料和仿生设计的汽车阻流板减阻机理 被引量:6
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作者 袁志群 谷正气 《中国机械工程》 EI CAS CSCD 北大核心 2019年第7期777-785,共9页
为了解决传统阻流板自身气动阻力过大的问题,提出了多孔介质阻流板和仿生阻流板两种新结构方案。利用计算流体动力学方法分析了两种方案在不同横摆角工况下的气动阻力变化规律,揭示了两种新结构的减阻机理;相比传统阻流板,两种新结构的... 为了解决传统阻流板自身气动阻力过大的问题,提出了多孔介质阻流板和仿生阻流板两种新结构方案。利用计算流体动力学方法分析了两种方案在不同横摆角工况下的气动阻力变化规律,揭示了两种新结构的减阻机理;相比传统阻流板,两种新结构的气动阻力峰值分别减小了3.3%和4.7%。在此基础上,提出了仿生阻流板和侧裙的组合结构方案,解决了传统阻流板中大横摆角时整车气动阻力增大的问题;相比传统阻流板,组合结构的气动阻力峰值减小了10.7%。比例模型风洞试验验证了所提方案的正确性。 展开更多
关键词 气动阻力 多孔介质 仿生阻 横摆角 侧裙 风洞试验
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变形多孔介质中多相流问题的数值方法
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作者 张钟鼎 王维彬 《安徽建筑工业学院学报(自然科学版)》 2001年第1期30-33,共4页
在比奥 ( Biot)的自适应理论的基础上建立变形多孔介质的多相流的控制方程 ,并给出其一相流耦合解答方法 。
关键词 多孔介质 多相 耦合解答 有限元法
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三元复合驱溶液周期性受限流动的数值模拟 被引量:2
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作者 李险峰 陈榕 +1 位作者 张年梅 赵得禄 《油田化学》 CAS CSCD 北大核心 2000年第4期369-373,377,共6页
用拉格朗日 欧拉模拟方法 ,采用并联毛细管道模型 ,定性地模拟研究了应用于三次强化采油中的三元复合驱 (ASP)溶液在多孔介质中的复杂流动行为。得到了低流速下ASP溶液在并联毛细管道中流动的速度场、应力场和压力场 ,同二次采油中驱油... 用拉格朗日 欧拉模拟方法 ,采用并联毛细管道模型 ,定性地模拟研究了应用于三次强化采油中的三元复合驱 (ASP)溶液在多孔介质中的复杂流动行为。得到了低流速下ASP溶液在并联毛细管道中流动的速度场、应力场和压力场 ,同二次采油中驱油剂 (水 )的结果进行了比较。结果表明 ,三元复合驱流体在多孔介质中流动时 ,表现出明显的非牛顿流特性 ;其应力场的分布具有不对称性 ,在溶液流经收缩喉道时 ,受到的阻力来自高剪切应力和法向应力 ,这些阻力要比具有相同流速的二次驱油液 (水 )高得多。因此 ,在相同的流速下ASP溶液的流动会产生更大的压力降。通过将计算结果同有关的实验结果进行定性的比较 ,验证了拉格朗日 欧拉算法的合理性。 展开更多
关键词 三元复合驱 多孔介质流 数值模拟 采油
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Pore structure and liquid flow velocity distribution in water-saturated porous media probed by MRI 被引量:3
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作者 吴爱祥 刘超 +2 位作者 尹升华 薛振林 陈勋 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2016年第5期1403-1409,共7页
Magnetic resonance imaging (MRI) was used to probe the structure and flow velocity within the interparticle space of a packed bed of agar beads under water-saturated condition. The images of the velocity field at th... Magnetic resonance imaging (MRI) was used to probe the structure and flow velocity within the interparticle space of a packed bed of agar beads under water-saturated condition. The images of the velocity field at three different flow rates were obtained. To determine the pore-parameter of the porous media, the internal structure of the bed was also obtained using image processing technique. The results show that the porosity of the sample is 31.28% and the fitting curve for the distribution of pore equivalent diameter follows Gaussian distribution. The velocity profiles do shift as the flow rate varies and the solution flow through the void space is not a homogeneous flow in any pores. The velocity distributions within the pore are roughly parabolic with the local maximum being near the center. About half of the velocity components are in the class of 0-1 cm/s. The frequency of lower velocity components is lower at higher flow rate, but to higher velocity components, it is just the opposite. 展开更多
关键词 magnetic resonance imaging porous media flow velocity POROSITY pore equivalent diameter
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耦合Navier-Stokes/Darcy模型多重网格方法的有限元实现(英文)
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作者 沈宇晶 韩丹夫 邵新平 《应用数学》 CSCD 北大核心 2016年第2期457-468,共12页
本文研究耦合Navier-Stokes/Darcy模型问题.构造一种从粗网格到细网格的有限元空间插值方法,不但简化了数值积分的单元匹配,也保证了数值积分的精度.利用基于有限元空间的多重网格方法,获得与直接法求解耦合问题误差相同的收敛阶,推广... 本文研究耦合Navier-Stokes/Darcy模型问题.构造一种从粗网格到细网格的有限元空间插值方法,不但简化了数值积分的单元匹配,也保证了数值积分的精度.利用基于有限元空间的多重网格方法,获得与直接法求解耦合问题误差相同的收敛阶,推广两重网格方法的结果. 展开更多
关键词 不可压缩 多孔介质流 NAVIER-STOKES方程 Darcy定律 多重网格方法 MI-NI有限元 Q2-Q1有限元
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NUMERICAL STUDY ON NATURAL CONVECTION HEAT TRANSFER INSIDE RECTANGULAR ENCLOSURE FILLED WITH ANISOTROPIC POROUS MEDIA
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作者 张靖周 李立国 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 1995年第1期57-63,共7页
Natural convection heat transfer inside horizontal rectangular enclosure filled with the anisotropic porous media, with isothermally heated bottom and cooled top while the vertical walls are adiabatic, is analyzed num... Natural convection heat transfer inside horizontal rectangular enclosure filled with the anisotropic porous media, with isothermally heated bottom and cooled top while the vertical walls are adiabatic, is analyzed numerically by applying the Brinkman model-a modified form of Darcy model giving consideration to the viscous effect. The results show that: (1)the permeability ratio (K*=Ky/Kx) is an important factor affecting natural convection heat transfer in the porous media. As K' decreases, the circulation intensity of the natural convectioncells increase significantly, resulting in an enhancement of heat transfer coefficient; (2)the increase of Darcy number (aa=Ky/H2) implies that the viscous effect is more significant. As Da≥10-, there exists a certain difference between the Darcy model and the Brinkman model. It is more significant at a lower permeability ratio. In particalar, with K*≤0. 25, the Nusselt number for Da=10-3 would differ form that of Darcy model up to an amount of 30K. The Darcy flow as depicted by Darcy model is no longer existing and an analysis neglecting the viscous effect will inevitably be of considerable error. 展开更多
关键词 heat transfer porous media natural convection numerical calculation non-Darcy flow
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Characteristics of unsteady flow in porous media while considering threshold pressure gradient with Green's function 被引量:2
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作者 曹仁义 陈岭 +2 位作者 Y.Zee Ma 刘雪莹 于柏慧 《Journal of Central South University》 SCIE EI CAS CSCD 2016年第1期201-208,共8页
The flow behavior in porous media with threshold pressure gradient(TPG) is more complex than Darcy flow and the equations of motion, and outer boundary and inner boundary with TPG are also different from Darcy flow fo... The flow behavior in porous media with threshold pressure gradient(TPG) is more complex than Darcy flow and the equations of motion, and outer boundary and inner boundary with TPG are also different from Darcy flow for unsteady flow of a producing well in a reservoir. An analytic method to solve this kind of problem is in a need of reestablishment. The classical method of Green's function and Newman product principle in a new way are used to solve the unsteady state flow problems of various shapes of well and reservoir while considering the TPG. Four Green's functions of point, line, band and circle while considering the TPG are achieved. Then, two well models of vertical well and horizontal well are built and simultaneously the function to calculate the moving boundary of each well model is provided. The results show that when considering TPG the pressure field is much different, which has a sudden pressure change, with a moving boundary in it. And the moving boundary of each well model increases with time but slows down rapidly, especially when the TGP is large. 展开更多
关键词 non-Darcy flow Green's function moving boundary threshold pressure gradient (TPG)
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Numerical analysis on forced convection enhancement in an annulus using porous ribs and nanoparticle addition to base fluid 被引量:6
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作者 Majid SIAVASHI Hamid Reza TALESH BAHRAMI +1 位作者 Ehsan AMINIAN Hamid SAFFARI 《Journal of Central South University》 SCIE EI CAS CSCD 2019年第5期1089-1098,共10页
Miniaturization of electronic equipment has forced researchers to devise more effective methods for dissipating the generated heat in these devices.In this study,two methods,including porous media inserting and adding... Miniaturization of electronic equipment has forced researchers to devise more effective methods for dissipating the generated heat in these devices.In this study,two methods,including porous media inserting and adding nanoparticles to the base fluid,are used to improve heat transfer in an annulus heated on both walls.To study porous media insert,porous ribs are used on the outer and inner walls independently.The results show that when porous ribs are placed on the outer wall,although the heat transfer enhances,the pressure drop increment is so considerable that performance number (the ratio of heat transfer enhancement pressure increment,PN) is less than unity for all porous rib heights and porous media permeabilities that are studied.On the other hand,the PN of cases where porous ribs were placed on the inner wall depends on the Darcy number (Da).For example,for ribs with Da=0.1 and Da=0.0001,the maximum performance number,PN=4,occurs at the porous ribs height to hydraulic diameter ratios H/Dh=1 and H/Dh=0.25.Under these conditions,heat transfer is enhanced by two orders of magnitude.It is found that adding 5% nanoparticles to the base fluid in the two aforementioned cases improves the Nusselt number and PN by 10%–40%. 展开更多
关键词 NANOFLUID porous media ANNULUS heat transfer enhancement internal flow
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Effect of absorption boundary layer on nonlinear flow in low permeability porous media 被引量:6
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作者 王学武 杨正明 +1 位作者 齐亚东 黄延章 《Journal of Central South University》 SCIE EI CAS 2011年第4期1299-1303,共5页
Taking low permeability cores of Daqing oilfield for example,the flow characteristics at low velocity were studied with the self-designed micro-flux measuring instrument.Considering the throat distribution and capilla... Taking low permeability cores of Daqing oilfield for example,the flow characteristics at low velocity were studied with the self-designed micro-flux measuring instrument.Considering the throat distribution and capillary model,the thickness of fluid boundary layer under different pressure gradients was calculated,and the mechanism and influencing factors of nonlinear percolation were discussed.The results show that the percolation curve of ultra-low rocks is nonlinear,and apparent permeability is not a constant which increases with pressure gradient.The absorption boundary layer decreases with the increase of pressure gradient,and changes significantly especially in low pressure gradient,which is the essence of nonlinear percolation.The absorption boundary layer is also found to be impacted by the surface property of rocks. 展开更多
关键词 low permeability reservoirs PERCOLATION absorption boundary layer capillary model
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Rheological behavior of hydrolyzed polyacrylamide solution flowing through a molecular weight adjusting device with porous medium
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作者 Lvhong Zhang Jiangtao Wang +3 位作者 Yuqi Zhang Bin Jiang Xiaoming Xiao Li Hao 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2016年第5期581-587,共7页
The separate-layer injection in different interlayers and the injection of the same-molecular-weight polymer so- lution in a layer are necessary in the polymer flooding process because of heterogeneous multilayer sand... The separate-layer injection in different interlayers and the injection of the same-molecular-weight polymer so- lution in a layer are necessary in the polymer flooding process because of heterogeneous multilayer sandstone reservoirs in EOR projects. To alleviate the matching problems between the layer permeability and the injected polymer molecular weight, a molecular weight adjusting device with porous medium was designed on the basis of mechanical degradation principle. In terms of four variables (polymer concentration, pore diameter, length of shear component and flow rate ), the theological behavior of hydrolyzed polyacrylamide (HPAM) solu- tion flowing through the device was investigated in detail. The change of these variables is able to control the shear rate of HPAM solutions through ceramic foam, and achieve the desired degree of shear degradation and the final theological parameters-viscosity loss, viscoelasticity and pressure drop. Therefore, a linear relationship between viscosity loss and shearing rate was established so as to obtain the targeted viscosity easily. Field tests in the Daqing Oil Field showed that the polymer molecular weight could drop 20% to 50%. In a word, the results could guide the industrial application of the novel device and the further study of polymer degradation flowing through the porous medium. 展开更多
关键词 Molecular weight adjusting device Polymer solution Rheological behavior Mechanical degradation Porous medium
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Determination of a Pore Structure Parameter of Porous Media by Analysis of Percolation Network Model 被引量:1
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作者 辛峰 王富民 +1 位作者 廖晖 李绍芬 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2000年第4期287-293,共7页
According to the simulation of nitrogen sorption process in porous media with three-dimensional network model, and the analysis for such a process with percolation theory, a new method is proposed to determine a pore ... According to the simulation of nitrogen sorption process in porous media with three-dimensional network model, and the analysis for such a process with percolation theory, a new method is proposed to determine a pore structure parameter--mean coordination number of pore network, which represents the connectivity among a great number of pores. Here the 'chamber-throat' model and the Weibull distribution are used to describe the pore geometry and the pore size distribution respectively. This method is based on the scaling law of percolation theory after both effects of sorption thermodynamics and pore size on the sorption hysteresis loops are considered. The results show that it is an effective procedure to calculate the mean coordination number for micro- and meso-porous media. 展开更多
关键词 coordination number porous media percolation theory network model SORPTION
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Measurement of Two Phase Flow in Porous Medium Using High-resolution Magnetic Resonance Imaging 被引量:4
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作者 蒋兰兰 宋永臣 +4 位作者 刘瑜 杨明军 朱宁军 王晓静 豆斌林 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2013年第1期85-93,共9页
Measurement of two phase flow in porous medium for sequestration was carried out using high-resolution magnetic resonance imaging (MRI) technique. The porous medium was a packed bed of glass beads. Spin echo multi seq... Measurement of two phase flow in porous medium for sequestration was carried out using high-resolution magnetic resonance imaging (MRI) technique. The porous medium was a packed bed of glass beads. Spin echo multi sequence was used to measure the distribution of CO2 and water in the porous medium. The intensity images show that the fluid distribution is non-uniform due to its viscosity and pore structure of porous medium. The velocity distribution of fluids is calculated from the saturation of water and porosity of porous medium. The experimental results show that fluid velocities vary with time and position. The capillary dispersion rate donated the effects of capillary, which was largest at water saturations of 0.45. The displacement process is different between in BZ-02 and BZ-2. The final water residual saturation depends on permeability and porosity. 展开更多
关键词 two phase flow porous medium magnetic resonance imaging SATURATION CO2 velocity DISPLACEMENT
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A New Numerical Solution of Fluid Flow in Stratigraphic Porous Media 被引量:1
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作者 XUYou-Sheng LIHua-Mei +1 位作者 GUOShang-Ping HUANGGuo-Xiang 《Communications in Theoretical Physics》 SCIE CAS CSCD 2004年第6期949-952,共4页
A new numerical technique based on a lattice-Boltzmann method is presented for analyzing the fluid flow in stratigraphic porous media near the earth's surface. The results obtained for the relations between porosi... A new numerical technique based on a lattice-Boltzmann method is presented for analyzing the fluid flow in stratigraphic porous media near the earth's surface. The results obtained for the relations between porosity, pressure,and velocity satisfy well the requirements of stratigraphic statistics and hence are helpful for a further study of the evolution of fluid flow in stratigraphic media. 展开更多
关键词 fluid flow stratigraphic porous media lattice-Boltzmann method
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Geoelectric response of porous media in water and grout injection processes 被引量:3
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作者 孙强 刘盛东 +1 位作者 姜春露 王勃 《Journal of Central South University》 SCIE EI CAS 2014年第12期4640-4645,共6页
Significant changes in spontaneous potential and exciting currents are observed during water and grout injection in a simulated porous media. Obvious correlations between the seepage flow field and the electric field ... Significant changes in spontaneous potential and exciting currents are observed during water and grout injection in a simulated porous media. Obvious correlations between the seepage flow field and the electric field in the porous media are identified.In this work, a detailed experimental study of geoelectric field variation occurring in water migration was reported by analyzing water and grout injection processes in a simulated porous media. The spontaneous potential varies linearly with the thickness of unsaturated porous media. Very interestingly, the spontaneous potential generated in the second grout injection exhibits some"memory" of previous grouting paths. The decreases in spontaneous potential observed during grout injection is very probably due to that the spontaneous potential variations are primarily caused by electro-filtration potential, as indicated by the far larger viscosity of grout compared to that of water. The geoelectric response can be utilized to effectively identify the grouting paths in water-bearing rocks. 展开更多
关键词 sandstone water injection spontaneous potential electro-filtration potential
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Slip flow and variable properties of viscoelastic fluid past a stretching surface embedded in a porous medium with heat generation 被引量:2
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作者 Ahmed M.Megahed 《Journal of Central South University》 SCIE EI CAS CSCD 2016年第4期991-999,共9页
This study examines theoretically and computationally the non-Newtonian boundary layer flow and heat transfer for a viscoelastic fluid over a stretching continuous sheet embedded in a porous medium with variable fluid... This study examines theoretically and computationally the non-Newtonian boundary layer flow and heat transfer for a viscoelastic fluid over a stretching continuous sheet embedded in a porous medium with variable fluid properties, slip velocity, and internal heat generation/absorption. The flow in boundary layer is considered to be generated solely by the stretching of the sheet adjacent to porous medium with boundary wall slip condition. Highly nonlinear momentum and thermal boundary layer equations governing the flow and heat transfer are reduced to set of nonlinear ordinary differential equations by appropriate transformation. The resulting ODEs are successfully solved numerically with the help of shooting method. Graphical results are shown for non-dimensional velocities and temperature. The effects of heat generation/absorption parameter, the porous parameter, the viscoelastic parameter, velocity slip parameter, variable thermal conductivity and the Prandtl number on the flow and temperature profiles are presented. Moreover, the local skin-friction coefficient and Nusselt number are presented. Comparison of numerical results is made with the earlier published results under limiting cases. 展开更多
关键词 viscoelastic fluid variable fluid properties slip velocity
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Three dimensional Couette flow and heat transfer through a porous medium with variable permeability
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作者 CHAUDHARYR.C. SHARMAPawanKumar 《Journal of Zhejiang University Science》 CSCD 2003年第2期181-185,共5页
This paper reports research on the effects of variations in injectio n velocity and perm eability on the heat transfer and flow through a highly porous medium betwee n two horizontal parallel plates situated at consta... This paper reports research on the effects of variations in injectio n velocity and perm eability on the heat transfer and flow through a highly porous medium betwee n two horizontal parallel plates situated at constant distance with constant suc tion by the upper plate.Due to this type of variation in injection velocity and in permeability the flow becomes three dimensional.The governing equations are sol ved by adopting complex variable notations to obtain the expressions for the ve locity and temperature field. The skin-friction along the main flow direction and rate of heat transfer are discussed with the help of graphs. 展开更多
关键词 Couette flow Porous medium Heat transfer Permeability injection/suction.
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A Class of Cauchy Problems for Porous Medium Equations with Strongly Nonlinear Sources and Convections
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作者 李海峰 《Chinese Quarterly Journal of Mathematics》 CSCD 1997年第2期42-50, ,共9页
In this paper we study existence of solutions of a class of Cauchy problems for porous medium equations with strongly nonlinear sources or absorptions and convections when the initial trace is a Radon measure μ on RN.
关键词 strongly nonlinear sources convectious porous medium equations Radon measure
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