An outburst of coal and gas is a major hazard in underground coal mining. It is generally accepted that an outburst occurs when certain conditions of stress, coal gassiness and physical-mechanical properties of coal a...An outburst of coal and gas is a major hazard in underground coal mining. It is generally accepted that an outburst occurs when certain conditions of stress, coal gassiness and physical-mechanical properties of coal are met. Outbursting is recognized as a two-step process, i.e., initiation and development. In this paper, we present a fully-coupled solid and fluid code to model the entire process of an outburst. The deformation, failure and fracture of solid （coal） are modeled with the discrete element method, and the flow of fluid （gas and water） such as free flow and Darcy flow are modeled with the lattice Boltzmann method. These two methods are coupled in a two-way process, i.e., the solid part provides a moving boundary condition and transfers momentum to the fluid, while the fluid exerts a dragging force upon the solid. Gas desorption from coal occurs at the solid-fluid boundary, and gas diffusion is implemented in the solid code where particles are assumed to be porous. A simple 2D example to simulate the process of an outburst with the model is also presented in this paper to demonstrate the capability of the coupled model.展开更多
In this work several relationships governing solid-fluid dynamic interaction forces were validated against experimental data for a single particle settling in a suspension of other smaller particles. It was observed t...In this work several relationships governing solid-fluid dynamic interaction forces were validated against experimental data for a single particle settling in a suspension of other smaller particles. It was observed that force relationships based on Lattice-Boltzmann simulations did not perform as well as other inter- action types tested. Nonetheless, it is apparent that, in the case of a suspension of different particle types, it is important that the correct choice is made as to how the contribution to the overall fluid-particle interaction force is split between buoyancy and drag. Experimental evidence clearly suggests that the ＂generalized＂ Archimedes＇ principle （where the foreign particle is considered to displace the whole suspension and not just the fluid） provides the best result.展开更多
On the basis of Hamilton principle. the equation of sonlid-liquid coupling vibration of pipe conveying fluid is deduced. An asymmetrical sonlid-liquid coupling damp matrix and a symmetrical solid-liquid coupling Sti...On the basis of Hamilton principle. the equation of sonlid-liquid coupling vibration of pipe conveying fluid is deduced. An asymmetrical sonlid-liquid coupling damp matrix and a symmetrical solid-liquid coupling Stiffness matrix are obtained. Using QR method , pipe’s nature frequencies are calculated. The curves of the first four orders of natural frequency-flow velocity of pipe waw given .The influence of flowing velocity ,pressure, solid-liquid coupling damp and solid-liquid coupling stiffness on natural frequency are discussed respectively.The dynamic respondence of the pipes for stepload with different flow velocity are calculated by Newmark method .It is found that,with the flow velocity increased, the nature frequency of the pipes reduced, increased,reduced again and so on.展开更多
Thermal fatigue (TF) is one of the most important factors that influence turbine's life.This paper establishes a 3D solid-fluid coupling model for a steady temperature analysis of a high-pressure turbine nozzle at...Thermal fatigue (TF) is one of the most important factors that influence turbine's life.This paper establishes a 3D solid-fluid coupling model for a steady temperature analysis of a high-pressure turbine nozzle at different turbine inlet gas total temperatures (TIGTTs).The temperature analysis supplies the temperature load for subsequent 3D finite element analysis to obtain the strain values.Following this,the prediction of the TF life is made on the basis of equivalent strain range.The results show that the strain increases with TIGTT,and the predicted TF life decreases correspondingly.This life prediction was confirmed by one TF test.展开更多
In modern chemical engineering processes, the involvement of solid/fluid interface is the most important component of process intensification techniques, such as confined membrane separation and catalysis. In the revi...In modern chemical engineering processes, the involvement of solid/fluid interface is the most important component of process intensification techniques, such as confined membrane separation and catalysis. In the review, we summarized the research progress of the latest theoretical and experimental works to elucidate the contribution of interface to the fluid properties and structures at nano-and micro-scale. We mainly focused on water, alcohol aqueous solution, and ionic liquids, because they are classical systems in interfacial science and/or widely involved in the industrialization process. Surface-induced fluids were observed in all reviewed systems and played a critical role in physicochemical properties and structures of outside fluid. It can even be regarded as a new interface, when the adsorption layer has a strong interaction with the solid surface. Finally, we proposed a perspective on scientific challenges in the modern chemical engineering processes and outlined future prospects.展开更多
A model for correlating the phase equilibria of solid-supercritical fluid systems has beendeveloped. The feature of the model is that it can be used to estimate the size of the solvent-soluteclusters and the local den...A model for correlating the phase equilibria of solid-supercritical fluid systems has beendeveloped. The feature of the model is that it can be used to estimate the size of the solvent-soluteclusters and the local density of the solvent in the solvent-solute clusters.展开更多
For solid-fluid interaction, one of the phase-density equations in diffuse interface models is degenerated to a "0 = 0" equation when the volume fraction of a certain phase takes the value of zero or unity. ...For solid-fluid interaction, one of the phase-density equations in diffuse interface models is degenerated to a "0 = 0" equation when the volume fraction of a certain phase takes the value of zero or unity. This is because the conservative variables in phasedensity equations include volume fractions. The degeneracy can be avoided by adding an artificial quantity of another material into the pure phase. However, nonphysical waves,such as shear waves in fluids, are introduced by the artificial treatment. In this paper,a transport diffuse interface model, which is able to treat zero/unity volume fractions, is presented for solid-fluid interaction. In the proposed model, a new formulation for phase densities is derived, which is unrelated to volume fractions. Consequently, the new model is able to handle zero/unity volume fractions, and nonphysical waves caused by artificial volume fractions are prevented. One-dimensional and two-dimensional numerical tests demonstrate that more accurate results can be obtained by the proposed model.展开更多
The elasto-plastic dynamic buckling and postbuckling phenomena of square plates subjected to in-plane solid-fluid slamming are investigated. According to the plate's response, the critical criteria for dynamic buc...The elasto-plastic dynamic buckling and postbuckling phenomena of square plates subjected to in-plane solid-fluid slamming are investigated. According to the plate's response, the critical criteria for dynamic buckling, dynamic plasticity and plastic collapse are defined, and the corresponding critical impulses are presented. Meanwhile, dynamic buckling modes and collapse models are observed. The effects of different boundary conditions and loading histories on the properties of buckling and postbuckling are discussed.展开更多
The solubility of stearic acid in supercritical CO2 with acetonitrile (CH3CN) cosolvent was measured at 318.15 K in the pressure range from 9.5 to 16.5 MPa, and the cosolvent concentration ranges from 0. 0 to 5.5 mol... The solubility of stearic acid in supercritical CO2 with acetonitrile (CH3CN) cosolvent was measured at 318.15 K in the pressure range from 9.5 to 16.5 MPa, and the cosolvent concentration ranges from 0. 0 to 5.5 mol% . The solubility increases with acetonitrile concentration and pressure, and it also increases with the apparent density of CO2 d1(moles of CO2 in per liter of fluid) at higher cosolvent concentrations. At lower d1, however, the solubility of the acid at lower acetonitrile concentrations is lower than that in pure CO2 provided that d1 is fixed, which is discussed qualitatively based on the clustering of the components in the system.展开更多
The vibration and control of pipes conveying fluid is studied. The solid-liquid coupling vibration equations of the pipe conveying fluid are deduced by Hamilton principle.The direct velocity feedback is used to contro...The vibration and control of pipes conveying fluid is studied. The solid-liquid coupling vibration equations of the pipe conveying fluid are deduced by Hamilton principle.The direct velocity feedback is used to control the pipe vibration. The whip response and control are discussed.展开更多
The solubilities of a number of solid solutes in supercritical CO2 have been correlated usingthe model proposed in previous paper. The numbers of CO2 in each CO2 -solute cluster and the localdensity of the CO2 in the...The solubilities of a number of solid solutes in supercritical CO2 have been correlated usingthe model proposed in previous paper. The numbers of CO2 in each CO2 -solute cluster and the localdensity of the CO2 in the clusters are predicted using the model. The results calculated agree fairly wellwith the experimental data.展开更多
To study the behavior of overlying strata and the likelihood of water inrush and quicksand with different mining sequences under an unconsolidated alluvium aquifer, a numerical model based on the fluid-solid coupling ...To study the behavior of overlying strata and the likelihood of water inrush and quicksand with different mining sequences under an unconsolidated alluvium aquifer, a numerical model based on the fluid-solid coupling theory was con- structed by FLAC3D. Simulation results revealed that the mining sequences had a significant influence on the seepage, dis- placement and failure characteristics of the overlying strata. In this kind of geological and hydrogeological conditions, the workface close to the outcrop of coal seam easily suffers from water inrush and quicksand during mining. In the simulation re- sults, the plastic zone, vertical displacement and pore water pressure in the overlying strata of the workface decrease more or less using the upward mining sequence than using the downward mining sequence. Therefore, the application of the upward mining sequence in the process of mining is preferential to prevent water inrush and quicksand.展开更多
In this paper,a mathematical model is developed to study the wave propagation in an infinite,homogeneous,transversely isotropic thermo-piezoelectric solid bar of circular cross-sections immersed in inviscid fluid.The ...In this paper,a mathematical model is developed to study the wave propagation in an infinite,homogeneous,transversely isotropic thermo-piezoelectric solid bar of circular cross-sections immersed in inviscid fluid.The present study is based on the use of the three-dimensional theory of elasticity.Three displacement potential functions are introduced to uncouple the equations of motion and the heat and electric conductions.The frequency equations are obtained for longitudinal and flexural modes of vibration and are studied based on Lord-Shulman,Green-Lindsay and Classical theory theories of thermo elasticity.The frequency equations of the coupled system consisting of cylinder and fluid are developed under the assumption of perfectslip boundary conditions at the fluid-solid interfaces,which are obtained for longitudinal and flexural modes of vibration and are studied numerically for PZT-4 material bar immersed in fluid.The computed non-dimensional frequencies are compared with Lord-Shulman,Green-Lindsay and Classical theory theories of thermo elasticity for longitudinal and flexural modes of vibrations.The dispersion curves are drawn for longitudinal and flexural modes of vibrations.Moreover,the dispersion of specific loss and damping factors are also analyzed for longitudinal and flexural modes of vibrations.展开更多
Suspension plasma spraying （SPS） can be utilized to manufacture finely structured coatings. In this process, liquid suspended with microor nano-sized solid particles is injected into a plasma jet. It involves drople...Suspension plasma spraying （SPS） can be utilized to manufacture finely structured coatings. In this process, liquid suspended with microor nano-sized solid particles is injected into a plasma jet. It involves droplet injection, solvent evaporation, and discharge, acceleration, heating, and melting of the solid particles. The high-speed and high-temperature particles final- ly impact on the substrate wall, to form a thin layer coating. In this study, a comprehensive numerical model was developed to simulate the dynamic behaviors of the suspension droplets and the solid particles, as well as the interactions between them and the plasma gas. The plasma gas was treated as compressible, multi-component, turbulent jet flow, using Navier-Stokes equations solved by the Eulerian method. The droplets and solid particles were treated as discrete Lagrangian entities, being tracked through the spray process. The drag force, Saffman lift force, and Brownian force were taken into account for the aerodynamic drag force, aerodynamic lift force, and random fluctuation force imposed on the particles. Spatial distributions of the micro- and nano-sized particles are given in this paper and their motion histories were observed. The key parameters of spray distribution, including particle size and axial spray distance, were also analyzed. The critical size of particle that follows well with the plasma jet was deduced for the specified operating conditions. Results show that in the downstream, the substrate influences the flow field structure and the particle characteristics. The appropriate spray distances were obtained for different microand nano-sized particles.展开更多
The dynamic behaviors of continuous and discrete flows in superhydrophobic microchannels are investigated with a lattice Boltzmann model.Typical characters of the superhydrophobic phenomenon are well observed from our...The dynamic behaviors of continuous and discrete flows in superhydrophobic microchannels are investigated with a lattice Boltzmann model.Typical characters of the superhydrophobic phenomenon are well observed from our simulations,including air trapped in the surface microstructures,high contact angles,low contact angle hysteresis,and reduced friction to fluid motions.Increasing the roughness of a hydrophobic surface can produce a large flow rate through the channel due to the trapped air,implying less friction or large apparent slip.The apparent slip length appears to be independent to the channel width and could be considered as a surface property.For a moving droplet,its behavior is affected by the surface roughness from two aspects:the contact angle difference between its two ends and the surface-liquid interfacial friction.As a consequence,the resulting droplet velocity changes with the surface roughness as firstly decreasing and then increasing.Simulation results are also compared with experimental observations and better agreement has been obtained than that from other numerical method.The information from this study could be valuable for microfluidic systems.展开更多
Micromorphic theory(MMT)envisions a material body as a continuous collection of deformable particles;each possesses finite size and inner structure.It is considered as the most successful top-down formulation of a two...Micromorphic theory(MMT)envisions a material body as a continuous collection of deformable particles;each possesses finite size and inner structure.It is considered as the most successful top-down formulation of a two-level continuum model,in which the deformation is expressed as a sum of macroscopic continuous deformation and internal microscopic deformation of the inner structure.In this work,the kinematics including the objective Eringen tensors is introduced.Balance laws are derived by requiring the energy equation to be form-invariant under the generalized Galilean transformation.The concept of material force and the balance law of pseudomomentum are generalized for MMT.An axiomatic approach is demonstrated in the formulation of constitutive equations for a generalized micromorphic thermoviscoelastic solid,generalized micromorphic fluid,micromorphic plasticity,and micromorphic electromagnetic-thermoelastic solid.Applications of MMT in micro/nanoscale are discussed.展开更多
The dehydration of water by dimethyl carbonate(DMC)is of great significance for its application in electrochemistry and oil industry.With the rapid development of nanomaterial,one-dimensional(e.g.carbon nanotube(CNT))...The dehydration of water by dimethyl carbonate(DMC)is of great significance for its application in electrochemistry and oil industry.With the rapid development of nanomaterial,one-dimensional(e.g.carbon nanotube(CNT))and two-dimensional(e.g.lamellar graphene)materials have been widely used for molecular sieving.In this work,the molecular behavior of dimethyl carbonate/water mixture confined in CNT with varying diameters was studied based on molecular dynamics simulation.Due to different van der Waals interactions for the components in the mixtures with the solid surface,DMC molecules are preferentially adsorbed on the inner surface of the pore wall and formed an adsorption layer.Comparing with the pure water molecules confined in CNT,the adsorption DMC layer shows notable effect on the local compositions and microstructures of water molecules under nanoconfinement,which may result in different water mobility.Our analysis shows that the surface-induced DMC molecules can destroy the hydrogen bonding network of water molecules and result in an uniform and dispersed distribution of water molecules in the tube.These clear molecular understandings can be useful in material design for membrane separation.展开更多
文摘An outburst of coal and gas is a major hazard in underground coal mining. It is generally accepted that an outburst occurs when certain conditions of stress, coal gassiness and physical-mechanical properties of coal are met. Outbursting is recognized as a two-step process, i.e., initiation and development. In this paper, we present a fully-coupled solid and fluid code to model the entire process of an outburst. The deformation, failure and fracture of solid （coal） are modeled with the discrete element method, and the flow of fluid （gas and water） such as free flow and Darcy flow are modeled with the lattice Boltzmann method. These two methods are coupled in a two-way process, i.e., the solid part provides a moving boundary condition and transfers momentum to the fluid, while the fluid exerts a dragging force upon the solid. Gas desorption from coal occurs at the solid-fluid boundary, and gas diffusion is implemented in the solid code where particles are assumed to be porous. A simple 2D example to simulate the process of an outburst with the model is also presented in this paper to demonstrate the capability of the coupled model.
文摘In this work several relationships governing solid-fluid dynamic interaction forces were validated against experimental data for a single particle settling in a suspension of other smaller particles. It was observed that force relationships based on Lattice-Boltzmann simulations did not perform as well as other inter- action types tested. Nonetheless, it is apparent that, in the case of a suspension of different particle types, it is important that the correct choice is made as to how the contribution to the overall fluid-particle interaction force is split between buoyancy and drag. Experimental evidence clearly suggests that the ＂generalized＂ Archimedes＇ principle （where the foreign particle is considered to displace the whole suspension and not just the fluid） provides the best result.
文摘On the basis of Hamilton principle. the equation of sonlid-liquid coupling vibration of pipe conveying fluid is deduced. An asymmetrical sonlid-liquid coupling damp matrix and a symmetrical solid-liquid coupling Stiffness matrix are obtained. Using QR method , pipe’s nature frequencies are calculated. The curves of the first four orders of natural frequency-flow velocity of pipe waw given .The influence of flowing velocity ,pressure, solid-liquid coupling damp and solid-liquid coupling stiffness on natural frequency are discussed respectively.The dynamic respondence of the pipes for stepload with different flow velocity are calculated by Newmark method .It is found that,with the flow velocity increased, the nature frequency of the pipes reduced, increased,reduced again and so on.
基金Project (No.50806040) supported by the National Natural Science Foundation of China
文摘Thermal fatigue (TF) is one of the most important factors that influence turbine's life.This paper establishes a 3D solid-fluid coupling model for a steady temperature analysis of a high-pressure turbine nozzle at different turbine inlet gas total temperatures (TIGTTs).The temperature analysis supplies the temperature load for subsequent 3D finite element analysis to obtain the strain values.Following this,the prediction of the TF life is made on the basis of equivalent strain range.The results show that the strain increases with TIGTT,and the predicted TF life decreases correspondingly.This life prediction was confirmed by one TF test.
基金supported by the National Natural Science Foundation of China [21878144, 21729601, 21838004]the Foundation for Innovative Research Groups of the National Natural Science Foundation of China [21921006]+3 种基金Project of Jiangsu Natural Science Foundation of China [BK20171464]Project of Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)the Kempe Foundation in Swedengrant of Ministry of Research and Innovation, CNCS-UEFISCDI, Romania, project number PN-III-P4-ID-PCCF-2016-0050, within PNCDI III and the Swedish Science Council (VR)。
文摘In modern chemical engineering processes, the involvement of solid/fluid interface is the most important component of process intensification techniques, such as confined membrane separation and catalysis. In the review, we summarized the research progress of the latest theoretical and experimental works to elucidate the contribution of interface to the fluid properties and structures at nano-and micro-scale. We mainly focused on water, alcohol aqueous solution, and ionic liquids, because they are classical systems in interfacial science and/or widely involved in the industrialization process. Surface-induced fluids were observed in all reviewed systems and played a critical role in physicochemical properties and structures of outside fluid. It can even be regarded as a new interface, when the adsorption layer has a strong interaction with the solid surface. Finally, we proposed a perspective on scientific challenges in the modern chemical engineering processes and outlined future prospects.
文摘A model for correlating the phase equilibria of solid-supercritical fluid systems has beendeveloped. The feature of the model is that it can be used to estimate the size of the solvent-soluteclusters and the local density of the solvent in the solvent-solute clusters.
基金Project supported by the National Natural Science Foundation of China(Nos.11702029,11771054,U1730118,91852207,and 11801036)the China Postdoctoral Science Foundation(No.2016M600967)
文摘For solid-fluid interaction, one of the phase-density equations in diffuse interface models is degenerated to a "0 = 0" equation when the volume fraction of a certain phase takes the value of zero or unity. This is because the conservative variables in phasedensity equations include volume fractions. The degeneracy can be avoided by adding an artificial quantity of another material into the pure phase. However, nonphysical waves,such as shear waves in fluids, are introduced by the artificial treatment. In this paper,a transport diffuse interface model, which is able to treat zero/unity volume fractions, is presented for solid-fluid interaction. In the proposed model, a new formulation for phase densities is derived, which is unrelated to volume fractions. Consequently, the new model is able to handle zero/unity volume fractions, and nonphysical waves caused by artificial volume fractions are prevented. One-dimensional and two-dimensional numerical tests demonstrate that more accurate results can be obtained by the proposed model.
基金The project is supported by National Natural Science Foundation of China.
文摘The elasto-plastic dynamic buckling and postbuckling phenomena of square plates subjected to in-plane solid-fluid slamming are investigated. According to the plate's response, the critical criteria for dynamic buckling, dynamic plasticity and plastic collapse are defined, and the corresponding critical impulses are presented. Meanwhile, dynamic buckling modes and collapse models are observed. The effects of different boundary conditions and loading histories on the properties of buckling and postbuckling are discussed.
基金Special article from the First International workshop on Green Chemistry, the University of ScienceTechnology of China, Hefei, China, May, 1998.Project (No. 29633020 and 629725308) supported by the National Natural Science Foundation of China.
文摘 The solubility of stearic acid in supercritical CO2 with acetonitrile (CH3CN) cosolvent was measured at 318.15 K in the pressure range from 9.5 to 16.5 MPa, and the cosolvent concentration ranges from 0. 0 to 5.5 mol% . The solubility increases with acetonitrile concentration and pressure, and it also increases with the apparent density of CO2 d1(moles of CO2 in per liter of fluid) at higher cosolvent concentrations. At lower d1, however, the solubility of the acid at lower acetonitrile concentrations is lower than that in pure CO2 provided that d1 is fixed, which is discussed qualitatively based on the clustering of the components in the system.
文摘The vibration and control of pipes conveying fluid is studied. The solid-liquid coupling vibration equations of the pipe conveying fluid are deduced by Hamilton principle.The direct velocity feedback is used to control the pipe vibration. The whip response and control are discussed.
文摘The solubilities of a number of solid solutes in supercritical CO2 have been correlated usingthe model proposed in previous paper. The numbers of CO2 in each CO2 -solute cluster and the localdensity of the CO2 in the clusters are predicted using the model. The results calculated agree fairly wellwith the experimental data.
文摘To study the behavior of overlying strata and the likelihood of water inrush and quicksand with different mining sequences under an unconsolidated alluvium aquifer, a numerical model based on the fluid-solid coupling theory was con- structed by FLAC3D. Simulation results revealed that the mining sequences had a significant influence on the seepage, dis- placement and failure characteristics of the overlying strata. In this kind of geological and hydrogeological conditions, the workface close to the outcrop of coal seam easily suffers from water inrush and quicksand during mining. In the simulation re- sults, the plastic zone, vertical displacement and pore water pressure in the overlying strata of the workface decrease more or less using the upward mining sequence than using the downward mining sequence. Therefore, the application of the upward mining sequence in the process of mining is preferential to prevent water inrush and quicksand.
文摘In this paper,a mathematical model is developed to study the wave propagation in an infinite,homogeneous,transversely isotropic thermo-piezoelectric solid bar of circular cross-sections immersed in inviscid fluid.The present study is based on the use of the three-dimensional theory of elasticity.Three displacement potential functions are introduced to uncouple the equations of motion and the heat and electric conductions.The frequency equations are obtained for longitudinal and flexural modes of vibration and are studied based on Lord-Shulman,Green-Lindsay and Classical theory theories of thermo elasticity.The frequency equations of the coupled system consisting of cylinder and fluid are developed under the assumption of perfectslip boundary conditions at the fluid-solid interfaces,which are obtained for longitudinal and flexural modes of vibration and are studied numerically for PZT-4 material bar immersed in fluid.The computed non-dimensional frequencies are compared with Lord-Shulman,Green-Lindsay and Classical theory theories of thermo elasticity for longitudinal and flexural modes of vibrations.The dispersion curves are drawn for longitudinal and flexural modes of vibrations.Moreover,the dispersion of specific loss and damping factors are also analyzed for longitudinal and flexural modes of vibrations.
基金Project supported by the National Natural Science Foundation of China （Nos. 11072216 and 11472245） and the Fundamental Research Funds for the Central Universities （No. 2012FZA4027）, China
文摘Suspension plasma spraying （SPS） can be utilized to manufacture finely structured coatings. In this process, liquid suspended with microor nano-sized solid particles is injected into a plasma jet. It involves droplet injection, solvent evaporation, and discharge, acceleration, heating, and melting of the solid particles. The high-speed and high-temperature particles final- ly impact on the substrate wall, to form a thin layer coating. In this study, a comprehensive numerical model was developed to simulate the dynamic behaviors of the suspension droplets and the solid particles, as well as the interactions between them and the plasma gas. The plasma gas was treated as compressible, multi-component, turbulent jet flow, using Navier-Stokes equations solved by the Eulerian method. The droplets and solid particles were treated as discrete Lagrangian entities, being tracked through the spray process. The drag force, Saffman lift force, and Brownian force were taken into account for the aerodynamic drag force, aerodynamic lift force, and random fluctuation force imposed on the particles. Spatial distributions of the micro- and nano-sized particles are given in this paper and their motion histories were observed. The key parameters of spray distribution, including particle size and axial spray distance, were also analyzed. The critical size of particle that follows well with the plasma jet was deduced for the specified operating conditions. Results show that in the downstream, the substrate influences the flow field structure and the particle characteristics. The appropriate spray distances were obtained for different microand nano-sized particles.
基金This work was supported by the Natural Sciences and Engineering Research Council of Canada(NSERC)and the Laurentian University Research Fund to JZ.
文摘The dynamic behaviors of continuous and discrete flows in superhydrophobic microchannels are investigated with a lattice Boltzmann model.Typical characters of the superhydrophobic phenomenon are well observed from our simulations,including air trapped in the surface microstructures,high contact angles,low contact angle hysteresis,and reduced friction to fluid motions.Increasing the roughness of a hydrophobic surface can produce a large flow rate through the channel due to the trapped air,implying less friction or large apparent slip.The apparent slip length appears to be independent to the channel width and could be considered as a surface property.For a moving droplet,its behavior is affected by the surface roughness from two aspects:the contact angle difference between its two ends and the surface-liquid interfacial friction.As a consequence,the resulting droplet velocity changes with the surface roughness as firstly decreasing and then increasing.Simulation results are also compared with experimental observations and better agreement has been obtained than that from other numerical method.The information from this study could be valuable for microfluidic systems.
文摘Micromorphic theory(MMT)envisions a material body as a continuous collection of deformable particles;each possesses finite size and inner structure.It is considered as the most successful top-down formulation of a two-level continuum model,in which the deformation is expressed as a sum of macroscopic continuous deformation and internal microscopic deformation of the inner structure.In this work,the kinematics including the objective Eringen tensors is introduced.Balance laws are derived by requiring the energy equation to be form-invariant under the generalized Galilean transformation.The concept of material force and the balance law of pseudomomentum are generalized for MMT.An axiomatic approach is demonstrated in the formulation of constitutive equations for a generalized micromorphic thermoviscoelastic solid,generalized micromorphic fluid,micromorphic plasticity,and micromorphic electromagnetic-thermoelastic solid.Applications of MMT in micro/nanoscale are discussed.
基金supported by the National Science Foundation of China(21878144,21729601 and 21838004)the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(21921006)+3 种基金Project of Jiangsu Natural Science Foundation of China(BK20171464)Project of Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)the Kempe Foundation in Swedena grant of Ministry of Research and Innovation,CNCS-UEFISCDI,project number PN-III-P4-ID-PCCF-2016-0050,within PNCDI III and the Swedish Science Council(VR)。
文摘The dehydration of water by dimethyl carbonate(DMC)is of great significance for its application in electrochemistry and oil industry.With the rapid development of nanomaterial,one-dimensional(e.g.carbon nanotube(CNT))and two-dimensional(e.g.lamellar graphene)materials have been widely used for molecular sieving.In this work,the molecular behavior of dimethyl carbonate/water mixture confined in CNT with varying diameters was studied based on molecular dynamics simulation.Due to different van der Waals interactions for the components in the mixtures with the solid surface,DMC molecules are preferentially adsorbed on the inner surface of the pore wall and formed an adsorption layer.Comparing with the pure water molecules confined in CNT,the adsorption DMC layer shows notable effect on the local compositions and microstructures of water molecules under nanoconfinement,which may result in different water mobility.Our analysis shows that the surface-induced DMC molecules can destroy the hydrogen bonding network of water molecules and result in an uniform and dispersed distribution of water molecules in the tube.These clear molecular understandings can be useful in material design for membrane separation.
