We numerically study the dynamics of particle crystals in annular microchannels by the immersed-boundary（IB）lattice Boltzmann（LB） coupled model, analyze the fluid-particle interactions during the migration of part...We numerically study the dynamics of particle crystals in annular microchannels by the immersed-boundary（IB）lattice Boltzmann（LB） coupled model, analyze the fluid-particle interactions during the migration of particles,and reveal the underlying mechanism of a particle focusing on the presence of fluid flows. The results show that the Reynolds and Dean numbers are key factors influencing the hydrodynamics of particles. The particles migrate onto their equilibrium tracks by adjusting the Reynolds and Dean numbers. Elliptical tracks of particles during hydrodynamic focusing can be predicted by the IB-LB model. Both the small Dean number and the small particle can lead to a small size of the focusing track. This work would possibly facilitate the utilization of annular microchannel flows to obtain microfluidic flowing crystals for advanced applications in biomedicine and materials synthesis.展开更多
The pressure drop in a microchannel Fischer-Tropsch reactor was investigated by means of a fluid dynamics model developed by the authors. The developed model takes into account roughness of the microchannel wall induc...The pressure drop in a microchannel Fischer-Tropsch reactor was investigated by means of a fluid dynamics model developed by the authors. The developed model takes into account roughness of the microchannel wall induced by catalyst particle deposition on the surface of the microchannel. The presented simulation procedure takes into account the variation of the synthesis product composition and the variation of thermal properties of the liquid and gas phases along the microchannel length as functions of pressure, temperature, conversion rate and chain growth coefficient. Liquid and gaseous products down flow are modeled in the annular flow approximation. The obtained results are presented for two general types of microchannels, i.e. for rough-walled and for smooth-walled microchannels. It is shown that fluid dynamics in rough-walled and smooth-walled microchannels are dramatically different. It is established that a mean critical diameter can be introduced. The microchannels with diameter below the mean critical value can experience operation difficulty due to by high aerodynamic resistance or can even become completely flooded.展开更多
This study is devoted to investigate the effect of induced magnetic field on fully developed magnetohydrodynamic(MHD)natural convection flow of electrically conducting fluid in a vertical annular micro-channel formed ...This study is devoted to investigate the effect of induced magnetic field on fully developed magnetohydrodynamic(MHD)natural convection flow of electrically conducting fluid in a vertical annular micro-channel formed by two concentric cylinders in the presence of imposed radial magnetic field.The velocity slip and temperature jump at the annular micro-channel surfaces are taken into account.The influence of induced magnetic field arising due to the motion of an electrically conducting fluid is taken into consideration.The governing equations of the motion are a set of simultaneous ordinary differential equations and their exact solutions in dimensionless form have been obtained under relevant boundary conditions.The expressions for velocity field,the induced magnetic field,temperature field,induced current density and skin friction have been obtained.A parametric study of the physical parameters is conducted and a representative set of numerical results for the velocity field,the induced magnetic field,temperature,induced current density,volume flow rate and skin friction are illustrated graphically to show interesting features of the radius ratio,rarefaction,fluid wall interaction,Hartmann number and the magnetic Prandtl number.During the course of investigation,it is found that for fixed value of Hartmann number,the skin friction profiles in the presence of induced magnetic field are higher compared to the case when the induced magnetic field is neglected.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 51728601 and 51771118the Natural Science Foundation of Jiangsu Province under Grant No BK20150600
文摘We numerically study the dynamics of particle crystals in annular microchannels by the immersed-boundary（IB）lattice Boltzmann（LB） coupled model, analyze the fluid-particle interactions during the migration of particles,and reveal the underlying mechanism of a particle focusing on the presence of fluid flows. The results show that the Reynolds and Dean numbers are key factors influencing the hydrodynamics of particles. The particles migrate onto their equilibrium tracks by adjusting the Reynolds and Dean numbers. Elliptical tracks of particles during hydrodynamic focusing can be predicted by the IB-LB model. Both the small Dean number and the small particle can lead to a small size of the focusing track. This work would possibly facilitate the utilization of annular microchannel flows to obtain microfluidic flowing crystals for advanced applications in biomedicine and materials synthesis.
文摘The pressure drop in a microchannel Fischer-Tropsch reactor was investigated by means of a fluid dynamics model developed by the authors. The developed model takes into account roughness of the microchannel wall induced by catalyst particle deposition on the surface of the microchannel. The presented simulation procedure takes into account the variation of the synthesis product composition and the variation of thermal properties of the liquid and gas phases along the microchannel length as functions of pressure, temperature, conversion rate and chain growth coefficient. Liquid and gaseous products down flow are modeled in the annular flow approximation. The obtained results are presented for two general types of microchannels, i.e. for rough-walled and for smooth-walled microchannels. It is shown that fluid dynamics in rough-walled and smooth-walled microchannels are dramatically different. It is established that a mean critical diameter can be introduced. The microchannels with diameter below the mean critical value can experience operation difficulty due to by high aerodynamic resistance or can even become completely flooded.
文摘This study is devoted to investigate the effect of induced magnetic field on fully developed magnetohydrodynamic(MHD)natural convection flow of electrically conducting fluid in a vertical annular micro-channel formed by two concentric cylinders in the presence of imposed radial magnetic field.The velocity slip and temperature jump at the annular micro-channel surfaces are taken into account.The influence of induced magnetic field arising due to the motion of an electrically conducting fluid is taken into consideration.The governing equations of the motion are a set of simultaneous ordinary differential equations and their exact solutions in dimensionless form have been obtained under relevant boundary conditions.The expressions for velocity field,the induced magnetic field,temperature field,induced current density and skin friction have been obtained.A parametric study of the physical parameters is conducted and a representative set of numerical results for the velocity field,the induced magnetic field,temperature,induced current density,volume flow rate and skin friction are illustrated graphically to show interesting features of the radius ratio,rarefaction,fluid wall interaction,Hartmann number and the magnetic Prandtl number.During the course of investigation,it is found that for fixed value of Hartmann number,the skin friction profiles in the presence of induced magnetic field are higher compared to the case when the induced magnetic field is neglected.
