We investigate the deionized water flows in microtubes made of quartz at high pressure under steady flow condition in situations that （i） pure nitrogen is used as the pressure source, and the experimental pressure i...We investigate the deionized water flows in microtubes made of quartz at high pressure under steady flow condition in situations that （i） pure nitrogen is used as the pressure source, and the experimental pressure is 0.1-1 MPa; （ii） the inner diameters of the experimental microtubes are from 6μm to 50μm. The results indicate that （i） the flow characteristics of the microtubes with inner diameters of 50μm, 20μm, 15μm,10μm agree well with the traditional macro flow mechanics, （ii） there are obvious warps as compared with theoretical values in 6μm microtubes.展开更多
The fractai expressions for flow rate and hydraulic conductivity for power-law fluids in a single capillary are derived based on the fractai nature of tortuous capillaries. Every parameter in the proposed expressions ...The fractai expressions for flow rate and hydraulic conductivity for power-law fluids in a single capillary are derived based on the fractai nature of tortuous capillaries. Every parameter in the proposed expressions has clear physical meaning. The flow rate and hydraulic conductivity for power-law fluids are found to be related to the tortuosity fractal dimension and the power-law index. The flow rate for power-law fluids increases with the increasing power-law index but decreases with the increasing tortuosity fractal dimension. Good agreement between the model predictions for flow in a fractai capillary and in a converging-diverging duct is obtained. The results suggest that the fractal capillary model can be used to model the power-law fluids with different rheologicai properties.展开更多
Whether polymer flooding can enhance displacement efficiency or not is still a problem under debate. Laboratory experiment, numerical simulation and core data analysis are the commonly used means to study polymer floo...Whether polymer flooding can enhance displacement efficiency or not is still a problem under debate. Laboratory experiment, numerical simulation and core data analysis are the commonly used means to study polymer flooding displacement efficiency. We discuss the limitations of these methods and employ molecular tribology to study the problem. The black-white ball action principle, i.e. the atom action model for describing the friction principle, is used to analyse the microscopic mechanism of oil displacement and describe the molecular interactions and displacement power during polymer flooding. Both tribology theory and dynamic theological test show that molecular interactions during polymer flooding are bigger than that during water flooding. It is concluded that displacement efficiency of water flooding may be higher than that of polymer flooding at particular area; while polymer flooding can weaken the heterogeneity significantly, decrease ineffective injection and enhance the total displacement efficiency.展开更多
A novel lattice Boltzmann model, in which we take the ratio of temperature difference in the temperature field to the environment one to be more than one order of magnitude than before, is developed to simulate two-di...A novel lattice Boltzmann model, in which we take the ratio of temperature difference in the temperature field to the environment one to be more than one order of magnitude than before, is developed to simulate two-dimensional reactive flows with fast chemistry. Different from the hybrid scheme for reactive flows [Comput. Phys. Commun. 129 （2000）267], this scheme is strictly in a pure lattice Doltzmann style （i.e., we solve the flow, temperature, and concentration fields using the lattice Boltzmann method only）. Different from the recent non-coupled lattice Boltzmann scheme lint. J. Mod. Phys. B 17（2003）197], the fluid density in our model is coupled directly with the temperature. Excellent agreement between the present results and other numerical data shows that this scheme is an efficient numerical method for practical reactive flows with fast chemistry.展开更多
Based on the homotopy mapping, a globally convergent method of parameter inversion for non-equilibrium convection-dispersion equations （CDEs） is developed. Moreover, in order to further improve the computational eff...Based on the homotopy mapping, a globally convergent method of parameter inversion for non-equilibrium convection-dispersion equations （CDEs） is developed. Moreover, in order to further improve the computational efficiency of the algorithm, a properly smooth function, which is derived from the sigmoid function, is employed to update the homotopy parameter during iteration. Numerical results show the feature of global convergence and high performance of this method. In addition, even the measurement quantities are heavily contaminated by noises, and a good solution can be found.展开更多
Based on the Bhatangar-Gross-Krook （BGK） models, numerical simulation using the lattice Boltzmann model is performed to investigate the optimized surface pattern in a micro-channel. In order to simulate the practica...Based on the Bhatangar-Gross-Krook （BGK） models, numerical simulation using the lattice Boltzmann model is performed to investigate the optimized surface pattern in a micro-channel. In order to simulate the practical situation correctly, a slip/no-slip boundary condition is applied with making several assumptions. To assess the validity and efficiency of the model, one benchmark problem with considering the surface patterns is studied. Numerical results show the value of rms velocity Vrms increases with the increasing ratio β and larger Reynolds number Re, higher fluctuation of the rms oscillating velocity. Furthermore, the results show that a good mixing effect can be obtained when Re is large enough and the ratio β is about 1.618,which is the appropriate choice, i.e. the well known golden section phenomenon.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 10302018 and 10572130, and the Natural Science Foundation of Zhejiang Province under Grant No Y605056.
文摘We investigate the deionized water flows in microtubes made of quartz at high pressure under steady flow condition in situations that （i） pure nitrogen is used as the pressure source, and the experimental pressure is 0.1-1 MPa; （ii） the inner diameters of the experimental microtubes are from 6μm to 50μm. The results indicate that （i） the flow characteristics of the microtubes with inner diameters of 50μm, 20μm, 15μm,10μm agree well with the traditional macro flow mechanics, （ii） there are obvious warps as compared with theoretical values in 6μm microtubes.
基金Supported by the National Natural Science Foundation of China under Grant No 10572052, and the Graduate Science and Technology Innovation Foundation of Huazhong University of Science and Technology under Grant No HF-05-15-2007-012.
文摘The fractai expressions for flow rate and hydraulic conductivity for power-law fluids in a single capillary are derived based on the fractai nature of tortuous capillaries. Every parameter in the proposed expressions has clear physical meaning. The flow rate and hydraulic conductivity for power-law fluids are found to be related to the tortuosity fractal dimension and the power-law index. The flow rate for power-law fluids increases with the increasing power-law index but decreases with the increasing tortuosity fractal dimension. Good agreement between the model predictions for flow in a fractai capillary and in a converging-diverging duct is obtained. The results suggest that the fractal capillary model can be used to model the power-law fluids with different rheologicai properties.
基金Supported by the National Natural Science Foundation of China under Grant No 10172028.
文摘Whether polymer flooding can enhance displacement efficiency or not is still a problem under debate. Laboratory experiment, numerical simulation and core data analysis are the commonly used means to study polymer flooding displacement efficiency. We discuss the limitations of these methods and employ molecular tribology to study the problem. The black-white ball action principle, i.e. the atom action model for describing the friction principle, is used to analyse the microscopic mechanism of oil displacement and describe the molecular interactions and displacement power during polymer flooding. Both tribology theory and dynamic theological test show that molecular interactions during polymer flooding are bigger than that during water flooding. It is concluded that displacement efficiency of water flooding may be higher than that of polymer flooding at particular area; while polymer flooding can weaken the heterogeneity significantly, decrease ineffective injection and enhance the total displacement efficiency.
文摘A novel lattice Boltzmann model, in which we take the ratio of temperature difference in the temperature field to the environment one to be more than one order of magnitude than before, is developed to simulate two-dimensional reactive flows with fast chemistry. Different from the hybrid scheme for reactive flows [Comput. Phys. Commun. 129 （2000）267], this scheme is strictly in a pure lattice Doltzmann style （i.e., we solve the flow, temperature, and concentration fields using the lattice Boltzmann method only）. Different from the recent non-coupled lattice Boltzmann scheme lint. J. Mod. Phys. B 17（2003）197], the fluid density in our model is coupled directly with the temperature. Excellent agreement between the present results and other numerical data shows that this scheme is an efficient numerical method for practical reactive flows with fast chemistry.
基金Supported by the K C Wang Education of Foundation of Hong Kong, and the National Natural Science Foundation of China under Grant Nos 10402043 and 10372106.
文摘Based on the homotopy mapping, a globally convergent method of parameter inversion for non-equilibrium convection-dispersion equations （CDEs） is developed. Moreover, in order to further improve the computational efficiency of the algorithm, a properly smooth function, which is derived from the sigmoid function, is employed to update the homotopy parameter during iteration. Numerical results show the feature of global convergence and high performance of this method. In addition, even the measurement quantities are heavily contaminated by noises, and a good solution can be found.
基金Supported by the National Natural Science Foundation of China under Grant No 10572130, the Research Grants Council of the Government of the HKSAR under Grant No PolyU5231/06E, the National Basic Research Programs of China under grant 2006CB708612.
文摘Based on the Bhatangar-Gross-Krook （BGK） models, numerical simulation using the lattice Boltzmann model is performed to investigate the optimized surface pattern in a micro-channel. In order to simulate the practical situation correctly, a slip/no-slip boundary condition is applied with making several assumptions. To assess the validity and efficiency of the model, one benchmark problem with considering the surface patterns is studied. Numerical results show the value of rms velocity Vrms increases with the increasing ratio β and larger Reynolds number Re, higher fluctuation of the rms oscillating velocity. Furthermore, the results show that a good mixing effect can be obtained when Re is large enough and the ratio β is about 1.618,which is the appropriate choice, i.e. the well known golden section phenomenon.
