The immersed boundary(IB)method is an approach to problems of fluid-structure interaction in which an elastic structure is immersed in a viscous incompressible fluid.The IB formulation of such problems uses a Lagrangi...The immersed boundary(IB)method is an approach to problems of fluid-structure interaction in which an elastic structure is immersed in a viscous incompressible fluid.The IB formulation of such problems uses a Lagrangian description of the structure and an Eulerian description of the fluid.It is well known that some versions of the IB method can suffer from poor volume conservation.Methods have been introduced to improve the volume-conservation properties of the IB method,but they either have been fairly specialized,or have used complex,nonstandard Eulerian finite-difference discretizations.In this paper,we use quasi-static and dynamic benchmark problems to investigate the effect of the choice of Eulerian discretization on the volume-conservation properties of a formally second-order accurate IB method.We consider both collocated and staggered-grid discretization methods.For the tests considered herein,the staggered-grid IB scheme generally yields at least a modest improvement in volume conservation when compared to cell-centered methods,and in many cases considered in this work,the spurious volume changes exhibited by the staggered-grid IB method are more than an order of magnitude smaller than those of the collocated schemes.We also compare the performance of cell-centered schemes that use either exact or approximate projection methods.We find that the volumeconservation properties of approximate projection IB methods depend strongly on the formulation of the projection method.When used with the IB method,we find that pressure-free approximate projection methods can yield extremely poor volume conservation,whereas pressure-increment approximate projection methods yield volume conservation that is nearly identical to that of a cell-centered exact projection method.展开更多
This paper presents a parallel method for simulating real-time 3D deformable objects using the volume preservation mass-spring system method on tetrahedron meshes.In general,the conventional mass-spring system is mani...This paper presents a parallel method for simulating real-time 3D deformable objects using the volume preservation mass-spring system method on tetrahedron meshes.In general,the conventional mass-spring system is manipulated as a force-driven method because it is fast,simple to implement,and the parameters can be controlled.However,the springs in traditional mass-spring system can be excessively elongated which cause severe stability and robustness issues that lead to shape restoring,simulation blow-up,and huge volume loss of the deformable object.In addition,traditional method that uses a serial process of the central processing unit(CPU)to solve the system in every frame cannot handle the complex structure of deformable object in real-time.Therefore,the first order implicit constraint enforcement for a mass-spring model is utilized to achieve accurate visual realism of deformable objects with tough constraint error.In this paper,we applied the distance constraint and volume conservation constraints for each tetrahedron element to improve the stability of deformable object simulation using the mass-spring system and behave the same as its real-world counterparts.To reduce the computational complexity while ensuring stable simulation,we applied a method that utilizes OpenGL compute shader,a part of OpenGL Shading Language(GLSL)that executes on the graphic processing unit(GPU)to solve the numerical problems effectively.We applied the proposed methods to experimental volumetric models,and volume percentages of all objects are compared.The average volume percentages of all models during the simulation using the mass-spring system,distance constraint,and the volume constraint method were 68.21%,89.64%,and 98.70%,respectively.The proposed approaches are successfully applied to improve the stability of mass-spring system and the performance comparison from our experimental tests also shows that the GPU-based method is faster than CPU-based implementation for all cases.展开更多
Re-initialization procedure in level-set interface capturing method were investigated. The algorithm accomplishes the re-initialization step through locking the interface positions. Better accuracy was obtained both o...Re-initialization procedure in level-set interface capturing method were investigated. The algorithm accomplishes the re-initialization step through locking the interface positions. Better accuracy was obtained both on the interface positions and the total fluid volume keeping. Though one more step of the interpolations is added in the procedure, there is no significant increase in total machine time spent.展开更多
To estimate the shape of tapered fibers using tapering machines with movable large-zone furnaces, a new calculation method is proposed based on the discrete deducing method and the principle of the volume conservation...To estimate the shape of tapered fibers using tapering machines with movable large-zone furnaces, a new calculation method is proposed based on the discrete deducing method and the principle of the volume conservation of the fiber materials. This method can estimate the tapering results, i.e., the shape of the tapered fibers, based on arbitrary moving parameters of the large-zone furnace and the fiber holders. The theoretical estimated results agree with the experimental measuring shape of the tapered fibers quite well.展开更多
This paper introduces the advanced MP-PIC-VOF model tailored for dense particle-laden flows with free surface,which has been developed and extensively tested across a set of validation cases found in literature and or...This paper introduces the advanced MP-PIC-VOF model tailored for dense particle-laden flows with free surface,which has been developed and extensively tested across a set of validation cases found in literature and original bulk particle water entry case.A distinctive feature of the MP-PIC method is its demonstrated ability to accurately capture the behavior of closely packed particles in a fluid,even in the absence of direct pairwise particle-particle interactions.At a closed packed limit,the MP-PIC method achieves the accurate representation of the state through the resolved mean particle velocity field and implementation of the velocity limiter in the inter-particle stress force.The new model integrates a trilinear interpolation technique,specifically adapted for unstructured hexahedral meshes,and a weighted least squares method for efficient gradient computation that operates at a sub-cell level,enabling more accurate calculation of inter-particle stress gradients.Other key contributions include the integration of hydrostatic pressure adaptation in the momentum equation and a volume-conservative alpha transport equation that ensures mass conservation during the transfer of the solid phase between distinct fluid phases.The coupling framework includes a range of coupled fluid-particle forces important for particles immersed in liquid,including a dense virtual mass force.The model's validation against experimental data and CFD-DEM-VOF results focuses on key flow parameters,specifically particle velocity,dispersion profile,and cavity evolution during bulk particle water entry.The model is shown to accurately simulate complex solid-liquid-gas interactions,demonstrating its potential for optimizing a wide range of complex industrial processes such as liquid fluidized beds,solid-liquid stirred tanks,and clarifiers.展开更多
This paper presents the development and validation of a fully coupled computational fluid dynamics—discrete element method—volume of fluid(CFD-DEM-VOF)model to simulate the complex behavior of particle-laden flows w...This paper presents the development and validation of a fully coupled computational fluid dynamics—discrete element method—volume of fluid(CFD-DEM-VOF)model to simulate the complex behavior of particle-laden flows with free surfaces.The coupling between the fluid and particle phases is established through the implemented continuity,momentum,and alpha transport equation.The coupled particle forces such as drag,pressure gradient,dense virtual mass,viscous,and interface forces are also integrated,with drag and dense virtual mass forces being dependent on local porosity.The integrated conservative alpha transport equation ensures phase volume conservation during interactions between particles and water.Additionally,we have implemented a trilinear interpolation method designed to operate on unstructured hexahedral meshes.This method has been tested for its ability to properly resolve the coupling effects in the numerical simulations,particularly in cases with a relatively low cell-size ratio.The model is validated through three distinct test cases:single particle water entry,dam break with particles,and water entry of a group of particles case.The experimental setup is built to study the dynamics of the water entry of a group of particles,where three key flow features are analyzed:the evolution of average particle velocity,cavity shape,and particle dispersion cloud profiles in water.The tests involve four different scenarios,including two different water levels(16.1 and 20.1 cm)and two different particle densities(2650 and 4000 kg/m3).High-speed videometry and particle tracking velocimetry(using ImageJ/TrackMate)methods are employed for experimental data acquisition.It is demonstrated that numerical results are in excellent agreement with theoretical predictions and experimental data.The study highlights the significance of vortices in cavity shaping and particle dispersion.The validated CFD-DEM-VOF model constitutes a robust tool for simulating particle-laden flows,contributing valuable insights into the complex interplay between particles and fluids.展开更多
基金support from American Heart Association grant 10SDG4320049National Science Foundation grants DMS 1016554 and OCI 1047734.
文摘The immersed boundary(IB)method is an approach to problems of fluid-structure interaction in which an elastic structure is immersed in a viscous incompressible fluid.The IB formulation of such problems uses a Lagrangian description of the structure and an Eulerian description of the fluid.It is well known that some versions of the IB method can suffer from poor volume conservation.Methods have been introduced to improve the volume-conservation properties of the IB method,but they either have been fairly specialized,or have used complex,nonstandard Eulerian finite-difference discretizations.In this paper,we use quasi-static and dynamic benchmark problems to investigate the effect of the choice of Eulerian discretization on the volume-conservation properties of a formally second-order accurate IB method.We consider both collocated and staggered-grid discretization methods.For the tests considered herein,the staggered-grid IB scheme generally yields at least a modest improvement in volume conservation when compared to cell-centered methods,and in many cases considered in this work,the spurious volume changes exhibited by the staggered-grid IB method are more than an order of magnitude smaller than those of the collocated schemes.We also compare the performance of cell-centered schemes that use either exact or approximate projection methods.We find that the volumeconservation properties of approximate projection IB methods depend strongly on the formulation of the projection method.When used with the IB method,we find that pressure-free approximate projection methods can yield extremely poor volume conservation,whereas pressure-increment approximate projection methods yield volume conservation that is nearly identical to that of a cell-centered exact projection method.
基金This work was supported by the Basic Science Research Program through the National Research Foundation of Korea(NRF-2019R1F1A1062752)funded by the Ministry of Education+1 种基金was funded by BK21 FOUR(Fostering Outstanding Universities for Research)(No.:5199990914048)and was also supported by the Soonchunhyang University Research Fund.
文摘This paper presents a parallel method for simulating real-time 3D deformable objects using the volume preservation mass-spring system method on tetrahedron meshes.In general,the conventional mass-spring system is manipulated as a force-driven method because it is fast,simple to implement,and the parameters can be controlled.However,the springs in traditional mass-spring system can be excessively elongated which cause severe stability and robustness issues that lead to shape restoring,simulation blow-up,and huge volume loss of the deformable object.In addition,traditional method that uses a serial process of the central processing unit(CPU)to solve the system in every frame cannot handle the complex structure of deformable object in real-time.Therefore,the first order implicit constraint enforcement for a mass-spring model is utilized to achieve accurate visual realism of deformable objects with tough constraint error.In this paper,we applied the distance constraint and volume conservation constraints for each tetrahedron element to improve the stability of deformable object simulation using the mass-spring system and behave the same as its real-world counterparts.To reduce the computational complexity while ensuring stable simulation,we applied a method that utilizes OpenGL compute shader,a part of OpenGL Shading Language(GLSL)that executes on the graphic processing unit(GPU)to solve the numerical problems effectively.We applied the proposed methods to experimental volumetric models,and volume percentages of all objects are compared.The average volume percentages of all models during the simulation using the mass-spring system,distance constraint,and the volume constraint method were 68.21%,89.64%,and 98.70%,respectively.The proposed approaches are successfully applied to improve the stability of mass-spring system and the performance comparison from our experimental tests also shows that the GPU-based method is faster than CPU-based implementation for all cases.
文摘Re-initialization procedure in level-set interface capturing method were investigated. The algorithm accomplishes the re-initialization step through locking the interface positions. Better accuracy was obtained both on the interface positions and the total fluid volume keeping. Though one more step of the interpolations is added in the procedure, there is no significant increase in total machine time spent.
基金supported by the National Natural Science Foundation of China (No.11078009)the Natural Science Foundation of Heilongjiang Province (No.A200914)
文摘To estimate the shape of tapered fibers using tapering machines with movable large-zone furnaces, a new calculation method is proposed based on the discrete deducing method and the principle of the volume conservation of the fiber materials. This method can estimate the tapering results, i.e., the shape of the tapered fibers, based on arbitrary moving parameters of the large-zone furnace and the fiber holders. The theoretical estimated results agree with the experimental measuring shape of the tapered fibers quite well.
基金supported by Sepro Mineral Systems through the Mitacs Accelerate project No:IT12396.
文摘This paper introduces the advanced MP-PIC-VOF model tailored for dense particle-laden flows with free surface,which has been developed and extensively tested across a set of validation cases found in literature and original bulk particle water entry case.A distinctive feature of the MP-PIC method is its demonstrated ability to accurately capture the behavior of closely packed particles in a fluid,even in the absence of direct pairwise particle-particle interactions.At a closed packed limit,the MP-PIC method achieves the accurate representation of the state through the resolved mean particle velocity field and implementation of the velocity limiter in the inter-particle stress force.The new model integrates a trilinear interpolation technique,specifically adapted for unstructured hexahedral meshes,and a weighted least squares method for efficient gradient computation that operates at a sub-cell level,enabling more accurate calculation of inter-particle stress gradients.Other key contributions include the integration of hydrostatic pressure adaptation in the momentum equation and a volume-conservative alpha transport equation that ensures mass conservation during the transfer of the solid phase between distinct fluid phases.The coupling framework includes a range of coupled fluid-particle forces important for particles immersed in liquid,including a dense virtual mass force.The model's validation against experimental data and CFD-DEM-VOF results focuses on key flow parameters,specifically particle velocity,dispersion profile,and cavity evolution during bulk particle water entry.The model is shown to accurately simulate complex solid-liquid-gas interactions,demonstrating its potential for optimizing a wide range of complex industrial processes such as liquid fluidized beds,solid-liquid stirred tanks,and clarifiers.
基金Sepro Mineral Systems through the Mitacs Accelerate project No:IT12396.We would also like to express our appreciation to Compute Canada and UBC ARC for supporting PIME Lab by granting us access to their high-performance computing platforms.The simulations presented in this work were conducted using the Compute Canada Beluga and UBC ARC Sockeye clusters,both of which contributed equally to the computational resources utilized.
文摘This paper presents the development and validation of a fully coupled computational fluid dynamics—discrete element method—volume of fluid(CFD-DEM-VOF)model to simulate the complex behavior of particle-laden flows with free surfaces.The coupling between the fluid and particle phases is established through the implemented continuity,momentum,and alpha transport equation.The coupled particle forces such as drag,pressure gradient,dense virtual mass,viscous,and interface forces are also integrated,with drag and dense virtual mass forces being dependent on local porosity.The integrated conservative alpha transport equation ensures phase volume conservation during interactions between particles and water.Additionally,we have implemented a trilinear interpolation method designed to operate on unstructured hexahedral meshes.This method has been tested for its ability to properly resolve the coupling effects in the numerical simulations,particularly in cases with a relatively low cell-size ratio.The model is validated through three distinct test cases:single particle water entry,dam break with particles,and water entry of a group of particles case.The experimental setup is built to study the dynamics of the water entry of a group of particles,where three key flow features are analyzed:the evolution of average particle velocity,cavity shape,and particle dispersion cloud profiles in water.The tests involve four different scenarios,including two different water levels(16.1 and 20.1 cm)and two different particle densities(2650 and 4000 kg/m3).High-speed videometry and particle tracking velocimetry(using ImageJ/TrackMate)methods are employed for experimental data acquisition.It is demonstrated that numerical results are in excellent agreement with theoretical predictions and experimental data.The study highlights the significance of vortices in cavity shaping and particle dispersion.The validated CFD-DEM-VOF model constitutes a robust tool for simulating particle-laden flows,contributing valuable insights into the complex interplay between particles and fluids.
