Reflections of a Korteweg-de Vries (KdV) solitary wave and an envelope solitary wave are studied by using the particle-in-cell simulation method. Defining the phase shift of the reflected solitary wave, we notice th...Reflections of a Korteweg-de Vries (KdV) solitary wave and an envelope solitary wave are studied by using the particle-in-cell simulation method. Defining the phase shift of the reflected solitary wave, we notice that there is a phase shift of the reflected KdV solitary wave, while there is no phase shift for an envelope solitary wave. It is also noted that the reflection of a KdV solitary wave at a solid boundary is equivalent to the head-on collision between two identical amplitude solitary waves.展开更多
A new approach to model viscosity in the conservation of momentum equations is presented and discussed. Coefficient of viscosity is modeled in such a way that it reaches asymptotically to infinity at the solid boundar...A new approach to model viscosity in the conservation of momentum equations is presented and discussed. Coefficient of viscosity is modeled in such a way that it reaches asymptotically to infinity at the solid boundary but still yields a finite value for the shear stress at the solid wall. Basic objective of this research is to show that certain combinations of higher order normal velocity gradients become zero at the solid boundary. Malled solutions for the Couette flow and Poiseuille flow between two parallel plates are obtained by modeling the coefficient of viscosity in a novel way. Also, viscous drag computed by our model is expected to yield higher values than the values predicted by the existing models, which matches closely to the experimental data.展开更多
The basic principle and numerical technique for simulating two three-dimensional bubbles near a free surface are studied in detail by using boundary element method. The singularities of influence coefficient matrix ar...The basic principle and numerical technique for simulating two three-dimensional bubbles near a free surface are studied in detail by using boundary element method. The singularities of influence coefficient matrix are eliminated using coordinate transformation and so-called 4π rule. The solid angle for the open surface is treated in direct method based on its definition. Several kinds of configurations for the bubbles and free surface have been investigated. The pressure contours during the evolution of bubbles are obtained in our model and can better illuminate the mechanism underlying the motions of bubbles and free surface. The bubble dynamics and their interactions have close relation with the standoff distances, buoyancy parameters and initial sizes of bubbles. Completely different bubble shapes, free surface motions, jetting patterns and pressure distributions under different parameters can be observed in our model, as demon- strated in our calculation results.展开更多
Smoothed particle hydrodynamics(SPH) method with numerical diffusive terms shows satisfactory stability and accuracy in some violent fluid–solid interaction problems. However, in most simulations, uniform particle ...Smoothed particle hydrodynamics(SPH) method with numerical diffusive terms shows satisfactory stability and accuracy in some violent fluid–solid interaction problems. However, in most simulations, uniform particle distributions are used and the multi-resolution, which can obviously improve the local accuracy and the overall computational efficiency, has seldom been applied. In this paper, a dynamic particle splitting method is applied and it allows for the simulation of both hydrostatic and hydrodynamic problems. The splitting algorithm is that, when a coarse(mother) particle enters the splitting region, it will be split into four daughter particles, which inherit the physical parameters of the mother particle. In the particle splitting process,conservations of mass, momentum and energy are ensured. Based on the error analysis, the splitting technique is designed to allow the optimal accuracy at the interface between the coarse and refined particles and this is particularly important in the simulation of hydrostatic cases. Finally, the scheme is validated by five basic cases, which demonstrate that the present SPH model with a particle splitting technique is of high accuracy and efficiency and is capable for the simulation of a wide range of hydrodynamic problems.Smoothed particle hydrodynamics(SPH)method with numerical diffusive terms shows satisfactory stability and accuracy in some violent fluid–solid interaction problems.However,in most simulations,uniform particle distributions are used and the multi-resolution,which can obviously improve the local accuracy and the overall computational efficiency,has seldom been applied.In this paper,a dynamic particle splitting method is applied and it allows for the simulation of both hydrostatic and hydrodynamic problems.The splitting algorithm is that,when a coarse(mother)particle enters the splitting region,it will be split into four daughter particles,which inherit the physical parameters of the mother particle.In the particle splitting process,conservations of mass,momentum and energy are ensured.Based on the error analysis,the splitting technique is designed to allow the optimal accuracy at the interface between the coarse and refined particles and this is particularly important in the simulation of hydrostatic cases.Finally,the scheme is validated by five basic cases,which demonstrate that the present SPH model with a particle splitting technique is of high accuracy and efficiency and is capable for the simulation of a wide range of hydrodynamic problems.展开更多
La(0.4)Sr(0.6)Co(0.2)Fe(0.7)Nb(0.1)O(3-δ)(LSCFN)was applied as both anode and cathode for symmetrical solid oxide fuel cells(SSOFCs)with zirconia based electrolyte.The cell with LSCFN electrode was fa...La(0.4)Sr(0.6)Co(0.2)Fe(0.7)Nb(0.1)O(3-δ)(LSCFN)was applied as both anode and cathode for symmetrical solid oxide fuel cells(SSOFCs)with zirconia based electrolyte.The cell with LSCFN electrode was fabricated by tape-casting and screen printing.Fabrication process was optimized firstly by comparing co-sintering and separate-sintering of electrode and electrolyte.To further improve the LSCFN electrode properties,oxygen ionic conductor of Gd(0.1)Ce(0.9)O(2-δ)(GDC)was added into the LSCFN electrode.The preferred composition of LSCFN-GDC composite electrode was found to be 1:1 in weight ratio with polarization resistance of 0.16Ωcm^2at 800~℃.The maximum power densities of LSCFN-GDC||GDC/YSZ/GDC||LSCFN-GDC tested in H2and CH4with 3%H2O were 395 m W cm^(-2)and 124 m W cm^(-2)at 850~?C,respectively,which were much higher than that of LSCFN||GDC/YSZ/GDC||LSCFN cells at same condition,possibly due to the extension of the triple phase boundary induced by the addition of GDC.The cell showed reasonable stability using H2and CH4with 3%H2O as fuels and no significant power output degradation was observed after total 200 h operation.展开更多
An advanced geometric modeler GEMS4.0 has been developed, in whichfeature representation is used at the highest level abstraction of a productmodel. Boundary representation is used at the bottom level, while CSG model...An advanced geometric modeler GEMS4.0 has been developed, in whichfeature representation is used at the highest level abstraction of a productmodel. Boundary representation is used at the bottom level, while CSG modelis adopted at the median level. A BRep data structure capable of modelingnon-manifold is adopted. NURBS representation is used for all curved surfaces.Quadric surfaces have dual representations consisting of their geometric datasuch as radius, center point, and center tals. Boundary representation of freeform surfaces is easily built by sweeping and skinning method with NURBSgeometry Set operations on curved solids with boundary representation areperformed by an evaluation process consisting of four steps. A file exchangefacility is provided for the conversion between product data described by STEPand product information generated by GEMS4.0展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 11275156,11547304 and 11505261
文摘Reflections of a Korteweg-de Vries (KdV) solitary wave and an envelope solitary wave are studied by using the particle-in-cell simulation method. Defining the phase shift of the reflected solitary wave, we notice that there is a phase shift of the reflected KdV solitary wave, while there is no phase shift for an envelope solitary wave. It is also noted that the reflection of a KdV solitary wave at a solid boundary is equivalent to the head-on collision between two identical amplitude solitary waves.
文摘A new approach to model viscosity in the conservation of momentum equations is presented and discussed. Coefficient of viscosity is modeled in such a way that it reaches asymptotically to infinity at the solid boundary but still yields a finite value for the shear stress at the solid wall. Basic objective of this research is to show that certain combinations of higher order normal velocity gradients become zero at the solid boundary. Malled solutions for the Couette flow and Poiseuille flow between two parallel plates are obtained by modeling the coefficient of viscosity in a novel way. Also, viscous drag computed by our model is expected to yield higher values than the values predicted by the existing models, which matches closely to the experimental data.
基金supported by the Funds for Creative Research Groups of China (50921001)the State Key Development Program for Basic Research of China (2010CB832704)
文摘The basic principle and numerical technique for simulating two three-dimensional bubbles near a free surface are studied in detail by using boundary element method. The singularities of influence coefficient matrix are eliminated using coordinate transformation and so-called 4π rule. The solid angle for the open surface is treated in direct method based on its definition. Several kinds of configurations for the bubbles and free surface have been investigated. The pressure contours during the evolution of bubbles are obtained in our model and can better illuminate the mechanism underlying the motions of bubbles and free surface. The bubble dynamics and their interactions have close relation with the standoff distances, buoyancy parameters and initial sizes of bubbles. Completely different bubble shapes, free surface motions, jetting patterns and pressure distributions under different parameters can be observed in our model, as demon- strated in our calculation results.
基金supported by the National Natural Science Foundation of China (Grant 51609049)the Science Foundation of Heilongjiang Province (Grant QC2016061)the Fundamental Research Funds for the Central Universities (Grants HEUGIP201701,HEUCFJ170109)
文摘Smoothed particle hydrodynamics(SPH) method with numerical diffusive terms shows satisfactory stability and accuracy in some violent fluid–solid interaction problems. However, in most simulations, uniform particle distributions are used and the multi-resolution, which can obviously improve the local accuracy and the overall computational efficiency, has seldom been applied. In this paper, a dynamic particle splitting method is applied and it allows for the simulation of both hydrostatic and hydrodynamic problems. The splitting algorithm is that, when a coarse(mother) particle enters the splitting region, it will be split into four daughter particles, which inherit the physical parameters of the mother particle. In the particle splitting process,conservations of mass, momentum and energy are ensured. Based on the error analysis, the splitting technique is designed to allow the optimal accuracy at the interface between the coarse and refined particles and this is particularly important in the simulation of hydrostatic cases. Finally, the scheme is validated by five basic cases, which demonstrate that the present SPH model with a particle splitting technique is of high accuracy and efficiency and is capable for the simulation of a wide range of hydrodynamic problems.Smoothed particle hydrodynamics(SPH)method with numerical diffusive terms shows satisfactory stability and accuracy in some violent fluid–solid interaction problems.However,in most simulations,uniform particle distributions are used and the multi-resolution,which can obviously improve the local accuracy and the overall computational efficiency,has seldom been applied.In this paper,a dynamic particle splitting method is applied and it allows for the simulation of both hydrostatic and hydrodynamic problems.The splitting algorithm is that,when a coarse(mother)particle enters the splitting region,it will be split into four daughter particles,which inherit the physical parameters of the mother particle.In the particle splitting process,conservations of mass,momentum and energy are ensured.Based on the error analysis,the splitting technique is designed to allow the optimal accuracy at the interface between the coarse and refined particles and this is particularly important in the simulation of hydrostatic cases.Finally,the scheme is validated by five basic cases,which demonstrate that the present SPH model with a particle splitting technique is of high accuracy and efficiency and is capable for the simulation of a wide range of hydrodynamic problems.
基金supported by the National Natural Science Foundation of China (No. 51402355)Natural Science Foundation of Beijing Project (Nos. LJ201531 and 2154056)+1 种基金Shanxi Province Project (No. MD2014-08)Guangdong Project (No. 201460720100025)
文摘La(0.4)Sr(0.6)Co(0.2)Fe(0.7)Nb(0.1)O(3-δ)(LSCFN)was applied as both anode and cathode for symmetrical solid oxide fuel cells(SSOFCs)with zirconia based electrolyte.The cell with LSCFN electrode was fabricated by tape-casting and screen printing.Fabrication process was optimized firstly by comparing co-sintering and separate-sintering of electrode and electrolyte.To further improve the LSCFN electrode properties,oxygen ionic conductor of Gd(0.1)Ce(0.9)O(2-δ)(GDC)was added into the LSCFN electrode.The preferred composition of LSCFN-GDC composite electrode was found to be 1:1 in weight ratio with polarization resistance of 0.16Ωcm^2at 800~℃.The maximum power densities of LSCFN-GDC||GDC/YSZ/GDC||LSCFN-GDC tested in H2and CH4with 3%H2O were 395 m W cm^(-2)and 124 m W cm^(-2)at 850~?C,respectively,which were much higher than that of LSCFN||GDC/YSZ/GDC||LSCFN cells at same condition,possibly due to the extension of the triple phase boundary induced by the addition of GDC.The cell showed reasonable stability using H2and CH4with 3%H2O as fuels and no significant power output degradation was observed after total 200 h operation.
文摘An advanced geometric modeler GEMS4.0 has been developed, in whichfeature representation is used at the highest level abstraction of a productmodel. Boundary representation is used at the bottom level, while CSG modelis adopted at the median level. A BRep data structure capable of modelingnon-manifold is adopted. NURBS representation is used for all curved surfaces.Quadric surfaces have dual representations consisting of their geometric datasuch as radius, center point, and center tals. Boundary representation of freeform surfaces is easily built by sweeping and skinning method with NURBSgeometry Set operations on curved solids with boundary representation areperformed by an evaluation process consisting of four steps. A file exchangefacility is provided for the conversion between product data described by STEPand product information generated by GEMS4.0