An analysis of tortuosity for streamlines in porous media is presented by coupling the circle and square models. It is assulued that some particles in porous media do not overlap and that fluid in porous media is incompressible. The relationship between tortuosity and porosity is attained with different configurations by using a statistical method. In addition, the tortuosity fractal dimension is expressed as a function of porosity. Those correlations do not include any empirical constant. The percolation threshold and tortuosity fractal dimension threshold of porous media are also presented as： φc = 0.32, DT,： = 1.07. The predicted correlations of the tortuosity and the porosity agree well with the existing experimental and simulated results.
The phase-change problem is solved by the migration-collision scheme of lattice Boltzmann method.After formula derivation,we find that this method can give a rigorous numerical value for the phase-change temperature,which is of crucial importance.One-dimensional solidification in half-space and two-dimensional solidification in a corner are simulated.The phase change temperature and the liquid-solid interface are both obtained,and the results conform to the analytical solution.
Xia Li,~1 Yang Liu,~2 Yousheng Xu,~(1,a) Meiying Ye,~1 and Fengmin Wu~1 1.Department of Physics,Zhejiang Normal University,Jinhua 321004,China 2.Department of Mechanical Engineering,The Hong Kong Polytechnic University,Kowloon,Hong Kong,China
Based on the multiple scattering method,this paper investigates a benchmark problem of the propagation of liquid surface waves over finite graphene (or honeycomb) structured arrays of cylinders.Comparing the graphene structured array with the square structured and with triangle structured arrays,it finds that the finite graphene structure can produce more complete band gaps than the other finite structures,and the finite graphene structure has less localized ability than the other finite structures.
Xuemei Liu,1,2 Yong Wei,1 Sheng Li,1 Yousheng Xu,1,Detang Lu,3 and Boming Yu 4 1) Department of Physics,Zhejiang Normal University,Jinhua 321004,Zhejiang,China 2) Hangzhou No.14 Middle School,Hangzhou 310006,China 3) Department of Modern Mechanics,University of Science and Technology of China,Hefei 230027,China 4) School of Physics,Huazhong University of Science and Technology,Wuahn 430074,China
Microbial fuel cell （MFC） is a novel environmental friendly energy device which has received great attention due to its technology for producing electricity directly fi-om organic or inorganic matter by using bacteria as catalyst. To date, many experiments have been carried out to achieve the maximum power output with advective flow through porous anode to the cathode in the MFC. However, the precise mechanical mechanism of flow through anode and the quantified relationship between electrode spacing and MFC performance are not yet clearly understood. It hasbeen found experimentally that the power output can be increased apparently at certain electrode spacing configuration. Based on these available experimental data, this paper investigates the effect of spacing between electrodes, the Darcy number of porous anode and the Reynolds number on the power production performance of MFC by using lattice Boltzmann method. The numerical simulation results present that the distance between electrodes significantly influences the flow velocity and residence time of the organic matter attached to the anode in the MFC. Moreover, it is found that the Darey number of porous anode and the Reynolds number can regulate the output efficiency of MFC. These results perform better understanding of the complex phenomena of MFC and will be helpful to optimize MFC design.
The dynamics of fluid flow through nanochannels is different from those in macroscopic systems. By using the molecular dynamics simulations, we investigate the influence of surface polarity of nanotube on the transport properties of the water fluid. The nanotube used here resembles the carbon nanotube, but carries charges of q on some atoms; overall, the nanotube is charge-neutral. Our simulation results show that water flux decreases sharply with the increasing of q for q 〈 1.6 e; however, the water flux for shells far away from nanotube wM1 increases slightly when q 〉 1.6 e. The mechanism behind the interesting phenomenon is discussed. Our findings may have implications for development of nano-fluidic devices and for understanding the movement of confined fluid inside the hydrophilic nanochannel.
