To solve the problem of inaccurate boundary identification and to eliminate the spurious pressure oscillation in the previously developed immersed smoothed point interpolation method(IS-PIM),a new sharp-interface IS-P...To solve the problem of inaccurate boundary identification and to eliminate the spurious pressure oscillation in the previously developed immersed smoothed point interpolation method(IS-PIM),a new sharp-interface IS-PIM combining mass conservation algorithm,called Sharp-ISPIM-Mass,is proposed in this work.Based on the so called sharp-interface method,the technique of quadratic local velocity reconstruction has been developed by combining with the mass conservation algorithm,which enables the present method improve the accuracy of the velocity field and satisfy the mass conservation condition near the boundary field.So the proposed method would not encounter the problem of spurious mass flux.In addition,a new form of FSI force evaluation considering pressure and viscous force to perform a whole function from the fluid domain to fictitious fluid domain is introduced,which makes the present method obtain more accurate results of FSI force than the original one.Through the numerical studies of a number of benchmark examples,the performance of the Sharp-ISPIM-Mass has been examined and illustrated.展开更多
The ghost fluid method(GFM)provides a simple way to simulate the interaction of immiscible materials.Especially,the modified GFM(MGFM)and its variants,based on the solutions of multi-material Riemann problems,are capa...The ghost fluid method(GFM)provides a simple way to simulate the interaction of immiscible materials.Especially,the modified GFM(MGFM)and its variants,based on the solutions of multi-material Riemann problems,are capable of faithfully taking into account the effects of nonlinear wave interaction and material property near the interface.Reasonable treatments for ghost fluid states or interface conditions have been shown to be crucial when applied to various interfacial phenomena involving large discontinuity and strong nonlinearity.These methods,therefore,have great potential in engineering applications.In this paper,we review the development of such methods.The methodologies of representative GFM-based algorithms for definition of interface conditions are illustrated and compared to each other.The research progresses in design principle and accuracy analysis are briefly described.Some steps and techniques for multi-dimensional extension are also summarized.In addition,we present some progresses in more challenging scientific problems,including a variety of fluid/solid-fluid/solid interactions with complex physical properties.Of course the challenges faced by researchers in this field are also discussed.展开更多
isoAdvector是一种新的几何VOF(Volume of Fluid)方法,虽然克服了传统几何VOF方法难以适用于三维空间任意多面体网格的缺点,但不能直接用来模拟涉及动网格技术的液舱晃荡.为此,引入了运动通量修正,并提出了面-界面交线运动修正,使得修...isoAdvector是一种新的几何VOF(Volume of Fluid)方法,虽然克服了传统几何VOF方法难以适用于三维空间任意多面体网格的缺点,但不能直接用来模拟涉及动网格技术的液舱晃荡.为此,引入了运动通量修正,并提出了面-界面交线运动修正,使得修正后的isoAdvector方法可以应用到液舱晃荡的模拟中.基于不同的VOF方法对非共振、共振受迫晃荡和单次冲击波面进行数值模拟,并将模拟结果与试验结果以及解析解进行了比较.结果表明:相对于代数VOF方法,采用修正后的isoAdvector方法获得的自由液面位置和整体水动力载荷精度更高;捕捉的波面没有褶皱,能够较好地模拟波面的翻卷和破碎.此外,提出了界面厚度的估计方法,分析了自由液面波高精度提高的原因.展开更多
Polycrystalline gallium nitride(GaN) thin films were deposited on Si(100) substrates via plasma-enhanced atomic layer deposition(PEALD) under optimal deposition parameters. In this work, we focus on the research of th...Polycrystalline gallium nitride(GaN) thin films were deposited on Si(100) substrates via plasma-enhanced atomic layer deposition(PEALD) under optimal deposition parameters. In this work, we focus on the research of the GaN/Si(100)interfacial properties. The x-ray reflectivity measurements show the clearly-resolved fringes for all the as-grown GaN films, which reveals a perfectly smooth interface between the GaN film and Si(100), and this feature of sharp interface is further confirmed by high resolution transmission electron microscopy(HRTEM). However, an amorphous interfacial layer(~ 2 nm) can be observed from the HRTEM images, and is determined to be mixture of Ga_xO_y and GaN by xray photoelectron spectroscopy. To investigate the effect of this interlayer on the GaN growth, an AlN buffer layer was employed for GaN deposition. No interlayer is observed between GaN and AlN, and GaN shows better crystallization and lower oxygen impurity during the initial growth stage than the GaN with an interlayer.展开更多
The salt intrusion phenomenon is caused by </span><u><span style="font-family:Verdana;">overexploitation</span></u><span style="font-family:Verdana;"> of aquifer...The salt intrusion phenomenon is caused by </span><u><span style="font-family:Verdana;">overexploitation</span></u><span style="font-family:Verdana;"> of aquifers in coastal areas. This physical phenomenon has been the subject of numerous </span><span style="font-family:Verdana;">studies and numerous methods have been proposed, with the aim of protecting the quality of the water in these aquifers. This work proposes a two-dimensional</span><span style="font-family:Verdana;"> saline intrusion model using the sharp interface approach and the level set method. It consists of a parabolic equation modeling the underground flow and a hyperbolic Equation (the level set equation) which makes it possible to track the evolution of the interface. High</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">-</span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">order numerical schemes such as the space scheme </span><u><span style="font-family:Verdana;">WENO5</span></u><span style="font-family:Verdana;"> and the third</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">-</span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">order time scheme </span><u><span style="font-family:Verdana;">TVD</span></u><span style="font-family:Verdana;">-</span><u><span style="font-family:Verdana;">RK</span></u><span style="font-family:Verdana;"> were used for the numerical resolution of the hyperbolic equation. To limit the tightening of the contour curves of the level set function, the </span><u><span style="font-family:Verdana;">redistanciation</span></u><span style="font-family:Verdana;"> or </span><u><span style="font-family:Verdana;">reinitialization</span></u><span style="font-family:Verdana;"> algorithm proposed by </span><u><span style="font-family:Verdana;">Sussma </span><i><span style="font-family:Verdana;展开更多
Body-fitted mesh generation has long been the bottleneck of simulating fluid flows involving complex geometries. Immersed boundary methods are non-boundary-conforming methods that have gained great popularity in the l...Body-fitted mesh generation has long been the bottleneck of simulating fluid flows involving complex geometries. Immersed boundary methods are non-boundary-conforming methods that have gained great popularity in the last two decades for their simplicity and flexibility, as well as their non-compromised accuracy. This paper presents a summary of some numerical algori- thms along the line of sharp interface direct forcing approaches and their applications in some practical problems. The algorithms include basic Navier-Stokes solvers, immersed boundary setup procedures, treatments of stationary and moving immersed bounda- ries, and fluid-structure coupling schemes. Applications of these algorithms in particulate flows, flow-induced vibrations, biofluid dynamics, and free-surface hydrodynamics are demonstrated. Some concluding remarks are made, including several future research directions that can further expand the application regime of immersed boundary methods.展开更多
This paper describes a novel sharp interface approach for modeling the cavitation phenomena in incompressible viscous flows. A one-field formulation is adopted for the vapor-liquid two-phase flow and the interface is ...This paper describes a novel sharp interface approach for modeling the cavitation phenomena in incompressible viscous flows. A one-field formulation is adopted for the vapor-liquid two-phase flow and the interface is tracked using a volume of fluid（VOF） method. Phase change at the interface is modeled using a simplification of the Rayleigh-Plesset equation. Interface jump conditions in velocity and pressure field are treated using a level set based ghost fluid method. The level set function is constructed from the volume fraction function. A marching cubes method is used to compute the interface area at the interface grid cells. A parallel fast marching method is employed to propagate interface information into the field. A description of the equations and numerical methods is presented. Results for a cavitating hydrofoil are compared with experimental data.展开更多
We propose a non-traditional finite element method with non-body-fitting grids to solve the matrix coefficient elliptic equations with sharp-edged interfaces. All possible situations that the interface cuts the grid a...We propose a non-traditional finite element method with non-body-fitting grids to solve the matrix coefficient elliptic equations with sharp-edged interfaces. All possible situations that the interface cuts the grid are considered. Both Diriehlet and Neumann boundary conditions are discussed. The coefficient matrix data can be given only on the grids, rather than an analytical function. Extensive numerical experiments show that this method is second order accurate in the L∞ norm.展开更多
In this paper, we combine the direct-forcing fictitious domain （DF/FD） method and the sharp interface method to resolve the problem of particle dielectrophoresis in two dimensions. The flow field and the motion of p...In this paper, we combine the direct-forcing fictitious domain （DF/FD） method and the sharp interface method to resolve the problem of particle dielectrophoresis in two dimensions. The flow field and the motion of particles are solved with the DF/FD method, the electric field is solved with the sharp inter- face method, and the electrostatic force on the particles is computed using the Maxwell stress tensor method. The proposed method is validated via three problems： effective conductivity of particle compos- ite between two planar plates, cell trapping in a channel, and motion of particles due to both conventional and traveling wave dielectrophoretic forces.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51639003,51809035)This work was supported by the High-technology ship research project of Ministry of Industry and Information Technology of China(Grant No.2017-614)+3 种基金the Joint Found for Equipment Pre Research and China Shipbuilding Industry Corporation(Grant No.614B042802-28)the Fundamental Research Funds for the Central Universities(Grant No.DUT2017TB05),the China Postdoctoral Science Foundation(Grant No.2018M641693)the Liaoning Revitalization Talents Program(Grant No.XLYC1908027)the Science Foundation of Hunan Province(Grant No.2019JJ50790)and the computation support of the Supercomputing Center of Dalian University of Technology.
文摘To solve the problem of inaccurate boundary identification and to eliminate the spurious pressure oscillation in the previously developed immersed smoothed point interpolation method(IS-PIM),a new sharp-interface IS-PIM combining mass conservation algorithm,called Sharp-ISPIM-Mass,is proposed in this work.Based on the so called sharp-interface method,the technique of quadratic local velocity reconstruction has been developed by combining with the mass conservation algorithm,which enables the present method improve the accuracy of the velocity field and satisfy the mass conservation condition near the boundary field.So the proposed method would not encounter the problem of spurious mass flux.In addition,a new form of FSI force evaluation considering pressure and viscous force to perform a whole function from the fluid domain to fictitious fluid domain is introduced,which makes the present method obtain more accurate results of FSI force than the original one.Through the numerical studies of a number of benchmark examples,the performance of the Sharp-ISPIM-Mass has been examined and illustrated.
基金supported under the National Natural Science Foundation of China(Nos.11872351 and U1730118)Science Challenge Project(No.JCKY2016212A502).
文摘The ghost fluid method(GFM)provides a simple way to simulate the interaction of immiscible materials.Especially,the modified GFM(MGFM)and its variants,based on the solutions of multi-material Riemann problems,are capable of faithfully taking into account the effects of nonlinear wave interaction and material property near the interface.Reasonable treatments for ghost fluid states or interface conditions have been shown to be crucial when applied to various interfacial phenomena involving large discontinuity and strong nonlinearity.These methods,therefore,have great potential in engineering applications.In this paper,we review the development of such methods.The methodologies of representative GFM-based algorithms for definition of interface conditions are illustrated and compared to each other.The research progresses in design principle and accuracy analysis are briefly described.Some steps and techniques for multi-dimensional extension are also summarized.In addition,we present some progresses in more challenging scientific problems,including a variety of fluid/solid-fluid/solid interactions with complex physical properties.Of course the challenges faced by researchers in this field are also discussed.
文摘isoAdvector是一种新的几何VOF(Volume of Fluid)方法,虽然克服了传统几何VOF方法难以适用于三维空间任意多面体网格的缺点,但不能直接用来模拟涉及动网格技术的液舱晃荡.为此,引入了运动通量修正,并提出了面-界面交线运动修正,使得修正后的isoAdvector方法可以应用到液舱晃荡的模拟中.基于不同的VOF方法对非共振、共振受迫晃荡和单次冲击波面进行数值模拟,并将模拟结果与试验结果以及解析解进行了比较.结果表明:相对于代数VOF方法,采用修正后的isoAdvector方法获得的自由液面位置和整体水动力载荷精度更高;捕捉的波面没有褶皱,能够较好地模拟波面的翻卷和破碎.此外,提出了界面厚度的估计方法,分析了自由液面波高精度提高的原因.
基金Project supported by the Fundamental Research Funds for the Central Universities(Grant Nos.FRF-BR-16-018A,FRF-TP-17-022A1,and FRF-TP-17-069A1)the National Natural Science Foundation of China(Grant Nos.61274134 and 51402064)+4 种基金USTB Start-up Program(Grant No.06105033)China Postdoctoral Science Foundation(Grant No.2018M631333)Beijing Natural Science Foundation(Grant Nos.2184112 and 4173077)Beijing Innovation and Research Base Fund(Grant No.Z161100005016095)the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2015387)
文摘Polycrystalline gallium nitride(GaN) thin films were deposited on Si(100) substrates via plasma-enhanced atomic layer deposition(PEALD) under optimal deposition parameters. In this work, we focus on the research of the GaN/Si(100)interfacial properties. The x-ray reflectivity measurements show the clearly-resolved fringes for all the as-grown GaN films, which reveals a perfectly smooth interface between the GaN film and Si(100), and this feature of sharp interface is further confirmed by high resolution transmission electron microscopy(HRTEM). However, an amorphous interfacial layer(~ 2 nm) can be observed from the HRTEM images, and is determined to be mixture of Ga_xO_y and GaN by xray photoelectron spectroscopy. To investigate the effect of this interlayer on the GaN growth, an AlN buffer layer was employed for GaN deposition. No interlayer is observed between GaN and AlN, and GaN shows better crystallization and lower oxygen impurity during the initial growth stage than the GaN with an interlayer.
文摘The salt intrusion phenomenon is caused by </span><u><span style="font-family:Verdana;">overexploitation</span></u><span style="font-family:Verdana;"> of aquifers in coastal areas. This physical phenomenon has been the subject of numerous </span><span style="font-family:Verdana;">studies and numerous methods have been proposed, with the aim of protecting the quality of the water in these aquifers. This work proposes a two-dimensional</span><span style="font-family:Verdana;"> saline intrusion model using the sharp interface approach and the level set method. It consists of a parabolic equation modeling the underground flow and a hyperbolic Equation (the level set equation) which makes it possible to track the evolution of the interface. High</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">-</span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">order numerical schemes such as the space scheme </span><u><span style="font-family:Verdana;">WENO5</span></u><span style="font-family:Verdana;"> and the third</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">-</span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">order time scheme </span><u><span style="font-family:Verdana;">TVD</span></u><span style="font-family:Verdana;">-</span><u><span style="font-family:Verdana;">RK</span></u><span style="font-family:Verdana;"> were used for the numerical resolution of the hyperbolic equation. To limit the tightening of the contour curves of the level set function, the </span><u><span style="font-family:Verdana;">redistanciation</span></u><span style="font-family:Verdana;"> or </span><u><span style="font-family:Verdana;">reinitialization</span></u><span style="font-family:Verdana;"> algorithm proposed by </span><u><span style="font-family:Verdana;">Sussma </span><i><span style="font-family:Verdana;
文摘Body-fitted mesh generation has long been the bottleneck of simulating fluid flows involving complex geometries. Immersed boundary methods are non-boundary-conforming methods that have gained great popularity in the last two decades for their simplicity and flexibility, as well as their non-compromised accuracy. This paper presents a summary of some numerical algori- thms along the line of sharp interface direct forcing approaches and their applications in some practical problems. The algorithms include basic Navier-Stokes solvers, immersed boundary setup procedures, treatments of stationary and moving immersed bounda- ries, and fluid-structure coupling schemes. Applications of these algorithms in particulate flows, flow-induced vibrations, biofluid dynamics, and free-surface hydrodynamics are demonstrated. Some concluding remarks are made, including several future research directions that can further expand the application regime of immersed boundary methods.
基金supported by the NSWC Carderock ILIR programby the US Office of Naval Research(Grant No.N000141-01-00-1-7)
文摘This paper describes a novel sharp interface approach for modeling the cavitation phenomena in incompressible viscous flows. A one-field formulation is adopted for the vapor-liquid two-phase flow and the interface is tracked using a volume of fluid（VOF） method. Phase change at the interface is modeled using a simplification of the Rayleigh-Plesset equation. Interface jump conditions in velocity and pressure field are treated using a level set based ghost fluid method. The level set function is constructed from the volume fraction function. A marching cubes method is used to compute the interface area at the interface grid cells. A parallel fast marching method is employed to propagate interface information into the field. A description of the equations and numerical methods is presented. Results for a cavitating hydrofoil are compared with experimental data.
文摘We propose a non-traditional finite element method with non-body-fitting grids to solve the matrix coefficient elliptic equations with sharp-edged interfaces. All possible situations that the interface cuts the grid are considered. Both Diriehlet and Neumann boundary conditions are discussed. The coefficient matrix data can be given only on the grids, rather than an analytical function. Extensive numerical experiments show that this method is second order accurate in the L∞ norm.
基金support from the National Natural Science Foundation of China(no.10872181)the National Basic Research Program of China(no.2006CB705400)+1 种基金Chinese Universities Scientific Fundthe Major Program of the National Natural Science Foundation of China(no.10632070)
文摘In this paper, we combine the direct-forcing fictitious domain （DF/FD） method and the sharp interface method to resolve the problem of particle dielectrophoresis in two dimensions. The flow field and the motion of particles are solved with the DF/FD method, the electric field is solved with the sharp inter- face method, and the electrostatic force on the particles is computed using the Maxwell stress tensor method. The proposed method is validated via three problems： effective conductivity of particle compos- ite between two planar plates, cell trapping in a channel, and motion of particles due to both conventional and traveling wave dielectrophoretic forces.
