In this paper,the lattice-Boltzmann method is used to investigate the droplet dynamics after impact on horizontal and inclined solid surface. The two-phase interparticle potential model is employed. The model is found...In this paper,the lattice-Boltzmann method is used to investigate the droplet dynamics after impact on horizontal and inclined solid surface. The two-phase interparticle potential model is employed. The model is found to possess a linear relation between the macroscopic properties( surface tension σ and contact angle α)and microscopic parameters( G,G t). The flow state of the droplet on the surface is analyzed in detail,and the effects of surface characteristic,impact velocity,impact angle,the viscosity and surface tension of the liquid are investigated,respectively. It is shown that the lattice-Boltzmann method can not only track exactly and automatically the interface,but also the simulation results have a good qualitative agreement with ones of the previous experimental and numerical studies.展开更多
The Lattice-Boltzmann method is an effective tool for solving fluid mechanics problems, but there isn't still a good scheme to determinate some parameters in Boltzmann equations. In this paper, a technique using e...The Lattice-Boltzmann method is an effective tool for solving fluid mechanics problems, but there isn't still a good scheme to determinate some parameters in Boltzmann equations. In this paper, a technique using evolutionary algorithm to automatically model Boltzmann equations is introduced. Numerical simulation shows that the designed scheme is fast and efficient.展开更多
Melt flow can significantly change the transport of heat and solute,dendrite growth.In this work,a phase-field lattice-Boltzmann model was developed to studyα-Mg dendrite growth of Mg-5wt%Zn alloy with forced convect...Melt flow can significantly change the transport of heat and solute,dendrite growth.In this work,a phase-field lattice-Boltzmann model was developed to studyα-Mg dendrite growth of Mg-5wt%Zn alloy with forced convection.Results show that the existence of forced convection and overlap of thermal and solute fields makes thermal and solute fields distribution nonuniform.Thus,the symmetry of dendrite morphology is destroyed.The solid temperature and concentration of the downstream dendrite tip front with forced convection are higher than that without forced convection,while the concentration of the upstream dendrite tip front is lower.The solute transport through melt flow will be hindered by developed sidebranching.With flow velocity increase,the upstream temperature gradient and thickness of the downstream solute enrichment layer increase gradually,while the downstream temperature gradient and thickness of the upstream solute enrichment layer decrease gradually.Meanwhile,the upstream dendrite tip velocity will increase gradually,while the downstream dendrite tip velocity will decrease at first and then unchanged.This study is helpful to establish the relationship betweenα-Mg dendrite growth and melt flow,which is beneficial to understand the role of melt flow on dendrite morphologies.展开更多
Nano-porous materials have excellent thermal insulation performance,whose microstructure and physical properties,however,have great influence on the thermal conductivity.To accurately describe the stochastic phase dis...Nano-porous materials have excellent thermal insulation performance,whose microstructure and physical properties,however,have great influence on the thermal conductivity.To accurately describe the stochastic phase distribution,a random internal morphology and structure generation-growth method,called the quartet structure generation set(QSGS),has been proposed in the present paper.The model was then imported into lattice Boltzmann algorithm as a fully resolved geometry and used to investigate the effects on heat transfer at the nanoscale.Furthermore,a three-dimensional Lattice Boltzmann method(LBM)D3Q15 was adopted to predict the nano-granule porous material effective thermal conductivity.This ideal method provided a significant advantage over similar porous media methods by directly controlling and adjusting of granule characteristics such as granule size,porosity and pore size distributions and studying their influence directly on thermal conductivity.To verify the accuracy of the proposed model,some experiments based on guarded hot plate meter(GHPM)were conducted.The results indicated that the simulation results agreed well with the experimental data and references values,which illustrated that this method was reliable to generate the microstructure of nano-granule.What’s more,the effects of pressure,core distribution probability,cd and density were investigated.There existed an optimal density(about 120 kg·m^(-3))making the effective thermal conductivity being minimum and an optimal core distribution probability about cd=0.1 making the uniformity being the best.In addition,the present approach is applicable in dealing with other porous materials as well.展开更多
Fully resolved numerical simulations of a micron-sized spherical particle residing on a surface with large-scale roughness are performed by using the Lattice-Boltzmann method.The aim is to investigate the influence of...Fully resolved numerical simulations of a micron-sized spherical particle residing on a surface with large-scale roughness are performed by using the Lattice-Boltzmann method.The aim is to investigate the influence of surface roughness on the detachment of fine drug particles from larger carrier particles for transporting fine drug particles in a DPI(dry powder inhaler).Often the carrier surface is modified by mechanical treatments for modifying the surface roughness in order to reduce the adhesion force of drug particles.Therefore,drug particle removal from the carrier surface is equivalent to the detachment of a sphere from a rough plane surface.Here a sphere with a diameter of 5μm at a particle Reynolds number of 1.0,3.5 and 10 are considered.The surface roughness is described as regularly spaced semi-cylindrical asperities(with the axes oriented normal to the flow direction)on a smooth surface.The influence of asperity distance and size ratio(i.e.the radius of the semi-cylinder to the particle radius,Rc/Rd)on particle adhesion and detachment are studied.The asperity distance is varied in the range 1.2<L/Rd<2 and the semi-cylinder radius between 0.5<Rc/Rd<0.75.The required particle resolution and domain size are appropriately selected based on numerical studies,and a parametric analysis is performed to investigate the relationship between the contact distance(i.e.half the distance between the particle contact points on two neighbouring semi-cylinders),the asperity distance,the size ratio,and the height of the particle centroid from the plane wall.The drag,lift and torque acting on the spherical particle are measured for different particle Reynolds numbers,asperity distances and sizes or diameters.The detachment of particles from rough surfaces can occur through lift-off,sliding and rolling,and the corresponding detachment models are constructed for the case of rough surfaces.These studies will be the basis for developing Lagrangian detachment models that eventually should allow the optimisation of dry powder inhaler performance through computational fluid dynamics.展开更多
Lattice-Boltzmann methods are versatile numerical modeling techniques capable of reproducing a wide variety of fluid-mechanical behavior.These methods are well suited to parallel implementation,particularly on the sin...Lattice-Boltzmann methods are versatile numerical modeling techniques capable of reproducing a wide variety of fluid-mechanical behavior.These methods are well suited to parallel implementation,particularly on the single-instruction multiple data(SIMD)parallel processing environments found in computer graphics processing units(GPUs).Although recent programming tools dramatically improve the ease with which GPUbased applications can be written,the programming environment still lacks the flexibility available to more traditional CPU programs.In particular,it may be difficult to develop modular and extensible programs that require variable on-device functionality with current GPU architectures.This paper describes a process of automatic code generation that overcomes these difficulties for lattice-Boltzmann simulations.It details the development of GPU-based modules for an extensible lattice-Boltzmann simulation package-LBHydra.The performance of the automatically generated code is compared to equivalent purpose written codes for both single-phase,multiphase,and multicomponent flows.The flexibility of the new method is demonstrated by simulating a rising,dissolving droplet moving through a porous medium with user generated lattice-Boltzmann models and subroutines.展开更多
基金Sponsored by the National Nature Science Foundation of China(Grant No.51276030,51176017)
文摘In this paper,the lattice-Boltzmann method is used to investigate the droplet dynamics after impact on horizontal and inclined solid surface. The two-phase interparticle potential model is employed. The model is found to possess a linear relation between the macroscopic properties( surface tension σ and contact angle α)and microscopic parameters( G,G t). The flow state of the droplet on the surface is analyzed in detail,and the effects of surface characteristic,impact velocity,impact angle,the viscosity and surface tension of the liquid are investigated,respectively. It is shown that the lattice-Boltzmann method can not only track exactly and automatically the interface,but also the simulation results have a good qualitative agreement with ones of the previous experimental and numerical studies.
文摘The Lattice-Boltzmann method is an effective tool for solving fluid mechanics problems, but there isn't still a good scheme to determinate some parameters in Boltzmann equations. In this paper, a technique using evolutionary algorithm to automatically model Boltzmann equations is introduced. Numerical simulation shows that the designed scheme is fast and efficient.
基金the National Natural Science Foundation of China(Nos.52074246,52275390,52205429,52201146)the National Defense Basic Scientific Research Program of China(Nos.JCKY2020408B002,WDZC2022-12)+2 种基金the Key Research and Development Program of Shanxi Province(Nos.202102050201011,202202050201014)the Science and Technology Major Project of Shanxi Province(Nos.20191102008,20191102007)the Guiding Local Science and Technology Development Projects by the Central Government(Nos.YDZJSX2022A025,YDZJSX2021A027).
文摘Melt flow can significantly change the transport of heat and solute,dendrite growth.In this work,a phase-field lattice-Boltzmann model was developed to studyα-Mg dendrite growth of Mg-5wt%Zn alloy with forced convection.Results show that the existence of forced convection and overlap of thermal and solute fields makes thermal and solute fields distribution nonuniform.Thus,the symmetry of dendrite morphology is destroyed.The solid temperature and concentration of the downstream dendrite tip front with forced convection are higher than that without forced convection,while the concentration of the upstream dendrite tip front is lower.The solute transport through melt flow will be hindered by developed sidebranching.With flow velocity increase,the upstream temperature gradient and thickness of the downstream solute enrichment layer increase gradually,while the downstream temperature gradient and thickness of the upstream solute enrichment layer decrease gradually.Meanwhile,the upstream dendrite tip velocity will increase gradually,while the downstream dendrite tip velocity will decrease at first and then unchanged.This study is helpful to establish the relationship betweenα-Mg dendrite growth and melt flow,which is beneficial to understand the role of melt flow on dendrite morphologies.
基金financially supported by the Natural Sciences Foundation of Shanghai,China(Grant No.15ZR1419900)。
文摘Nano-porous materials have excellent thermal insulation performance,whose microstructure and physical properties,however,have great influence on the thermal conductivity.To accurately describe the stochastic phase distribution,a random internal morphology and structure generation-growth method,called the quartet structure generation set(QSGS),has been proposed in the present paper.The model was then imported into lattice Boltzmann algorithm as a fully resolved geometry and used to investigate the effects on heat transfer at the nanoscale.Furthermore,a three-dimensional Lattice Boltzmann method(LBM)D3Q15 was adopted to predict the nano-granule porous material effective thermal conductivity.This ideal method provided a significant advantage over similar porous media methods by directly controlling and adjusting of granule characteristics such as granule size,porosity and pore size distributions and studying their influence directly on thermal conductivity.To verify the accuracy of the proposed model,some experiments based on guarded hot plate meter(GHPM)were conducted.The results indicated that the simulation results agreed well with the experimental data and references values,which illustrated that this method was reliable to generate the microstructure of nano-granule.What’s more,the effects of pressure,core distribution probability,cd and density were investigated.There existed an optimal density(about 120 kg·m^(-3))making the effective thermal conductivity being minimum and an optimal core distribution probability about cd=0.1 making the uniformity being the best.In addition,the present approach is applicable in dealing with other porous materials as well.
基金supported by the Chinese Fundamental Research Funds for the Central Universities of the project No.2020kfyXJJS065.
文摘Fully resolved numerical simulations of a micron-sized spherical particle residing on a surface with large-scale roughness are performed by using the Lattice-Boltzmann method.The aim is to investigate the influence of surface roughness on the detachment of fine drug particles from larger carrier particles for transporting fine drug particles in a DPI(dry powder inhaler).Often the carrier surface is modified by mechanical treatments for modifying the surface roughness in order to reduce the adhesion force of drug particles.Therefore,drug particle removal from the carrier surface is equivalent to the detachment of a sphere from a rough plane surface.Here a sphere with a diameter of 5μm at a particle Reynolds number of 1.0,3.5 and 10 are considered.The surface roughness is described as regularly spaced semi-cylindrical asperities(with the axes oriented normal to the flow direction)on a smooth surface.The influence of asperity distance and size ratio(i.e.the radius of the semi-cylinder to the particle radius,Rc/Rd)on particle adhesion and detachment are studied.The asperity distance is varied in the range 1.2<L/Rd<2 and the semi-cylinder radius between 0.5<Rc/Rd<0.75.The required particle resolution and domain size are appropriately selected based on numerical studies,and a parametric analysis is performed to investigate the relationship between the contact distance(i.e.half the distance between the particle contact points on two neighbouring semi-cylinders),the asperity distance,the size ratio,and the height of the particle centroid from the plane wall.The drag,lift and torque acting on the spherical particle are measured for different particle Reynolds numbers,asperity distances and sizes or diameters.The detachment of particles from rough surfaces can occur through lift-off,sliding and rolling,and the corresponding detachment models are constructed for the case of rough surfaces.These studies will be the basis for developing Lagrangian detachment models that eventually should allow the optimisation of dry powder inhaler performance through computational fluid dynamics.
基金performed under the auspices of the U.S.Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344support by the National Science Foundation(NSF)under Grant No.DMS-0724560,Grant No.EAR-0838541,and Grant No.EAR-0941666the Department of Energy(DOE)under Grant No.DE-EE0002764.
文摘Lattice-Boltzmann methods are versatile numerical modeling techniques capable of reproducing a wide variety of fluid-mechanical behavior.These methods are well suited to parallel implementation,particularly on the single-instruction multiple data(SIMD)parallel processing environments found in computer graphics processing units(GPUs).Although recent programming tools dramatically improve the ease with which GPUbased applications can be written,the programming environment still lacks the flexibility available to more traditional CPU programs.In particular,it may be difficult to develop modular and extensible programs that require variable on-device functionality with current GPU architectures.This paper describes a process of automatic code generation that overcomes these difficulties for lattice-Boltzmann simulations.It details the development of GPU-based modules for an extensible lattice-Boltzmann simulation package-LBHydra.The performance of the automatically generated code is compared to equivalent purpose written codes for both single-phase,multiphase,and multicomponent flows.The flexibility of the new method is demonstrated by simulating a rising,dissolving droplet moving through a porous medium with user generated lattice-Boltzmann models and subroutines.
