The purpose of the present paper is to introduce a simple two-part multi-phase model for the sediment transport problems based on the incompressible smoothed particle hydrodynamics（ISPH） method. The proposed model s...The purpose of the present paper is to introduce a simple two-part multi-phase model for the sediment transport problems based on the incompressible smoothed particle hydrodynamics（ISPH） method. The proposed model simulates the movement of sediment particles in two parts. The sediment particles are classified into three categories, including the motionless particles, moving particles behave like a rigid body, and moving particles with a pseudo fluid behavior. The criterion for the classification of sediment particles is the Bingham rheological model. Verification of the present model is performed by simulation of the dam break waves on movable beds with different conditions and the bed scouring under steady flow condition. Comparison of the present model results, the experimental data and available numerical results show that it has good ability to simulate flow pattern and sediment transport.展开更多
Smoothed particle hydrodynamics （SPH） is a Lagrangian, meshfree particle method and has been widely applied to diffe- rent areas in engineering and science. Since its original extension to modeling free surface flow...Smoothed particle hydrodynamics （SPH） is a Lagrangian, meshfree particle method and has been widely applied to diffe- rent areas in engineering and science. Since its original extension to modeling free surface flows by Monaghan in 1994, SPH has been gradually developed into an attractive approach for modeling viscous incompressible fluid flows. This paper presents an overview on the recent progresses of SPH in modeling viscous incompressible flows in four major aspects which are closely related to the computational accuracy of SPH simulations. The advantages and disadvantages of different SPH particle approximation sche- mes, pressure field solution approaches, solid boundary treatment algorithms and particle adapting algorithms are described and analyzed. Some new perspectives and fuRtre trends in SPH modeling of viscous incompressible flows are discussed.展开更多
In order to capture stable and realistic microscopic features of fluid surface, a surface tension and adhesion method based on implicit incompressible SPH （smoothed particle hydrodynamics） is presented in this paper...In order to capture stable and realistic microscopic features of fluid surface, a surface tension and adhesion method based on implicit incompressible SPH （smoothed particle hydrodynamics） is presented in this paper. It gives a steady and fast tension model and can solve the problem of not considering adhesion. Molecular cohesion and surface minimization are considered for surface tension, and adhesion is added to show the microscopic characteristics of the surface. To simulate surface tension and adhesion stably and efficiently, the surface tension and adhesion model is integrated to an implicit incompressible SPH method. The experimental results show that the method can better simulate surface features in a variety of scenarios compared with previous methods and meanwhile ensure stability and efficiency.展开更多
Predictive-corrective incompressible smoothed particle hydrodynamics (PCISPH) is an efficient SPH variation originally developed for computer graphics. Its application in modeling physics-focused fluid flows has not y...Predictive-corrective incompressible smoothed particle hydrodynamics (PCISPH) is an efficient SPH variation originally developed for computer graphics. Its application in modeling physics-focused fluid flows has not yet been reported. In this work, an improved PCISPH method is presented for physics-focused fluid flow modeling. Different from traditional weakly-compressible SPH (WCSPH) and incompressible SPH (ISPH), PCISPH satisfies the incompressibility requirement at the particle level without a predefined equation of state. The pressure is obtained using an iterative predictive-corrective scheme at each individual particle. The presented PCISPH allows much larger time steps compared with WCSPH. It also avoids the time-consuming solution of Pressure Poisson Equation (PPE) in ISPH. Consequently, the PCISPH has high computational efficiency even with millions of computational particles. To ensure physically correct modeling of fluid flows, we employ several techniques to enhance the accuracy and stability of the PCISPH:(1) the continuity equation is used to predict density, replacing the mass summation approach used in the original PCISPH,(2) numerical diffusion and pressure smoothing are introduced to improve the pressure computation,(3) a generalized boundary treatment approach which can handle arbitrarily complex geometries is employed,(4) an adaptive time-stepping algorithm is used, allowing efficient simulation as well as ensuring stability. The performance of the improved PCISPH is systematically investigated using three standard SPH validation cases. Comparisons between the improved PCISPH and the state-of-the-art 5 - SPH are presented. It is found that the improved PCISPH gives numerical results as accurate as J - SPH, except for having moderate temporal pressure oscillations. However, the numerical results show that the improved PCISPH is approximately five times faster than 8 -SPH. The improved PCISPH method shows to be a promising tool for large-scale three-dimensional fluid flow modeling.展开更多
A fully Lagrangian algorithm for numerical simulation of fluid-elastic structure interaction(FSI)problems is developed based on the Smoothed Particle Hydrodynamics(SPH)method.The developed method corresponds to incomp...A fully Lagrangian algorithm for numerical simulation of fluid-elastic structure interaction(FSI)problems is developed based on the Smoothed Particle Hydrodynamics(SPH)method.The developed method corresponds to incompressible fluid flows and elastic structures.Divergence-free(projection based)incompressible SPH(ISPH)is used for the fluid phase,while the equations of motion for structural dynamics are solved using Total Lagrangian SPH(TLSPH)method.The temporal pressure noise can occur at the free surface and fluid-solid interfaces due to errors associated with the truncated kernels.A FSI particle shifting scheme is implemented to produce sufficiently homogeneous particle distributions to enable stable,accurate,converged solutions without noise in the pressure field.The coupled algorithm,with the addition of proposed particle shifting scheme,is able to provide the possibility of simultaneous integration of governing equations for all particles,regardless of their material type.This remedy without need for tuning a new parameter,resolves the unphysical discontinuity beneath the interface of fluid-solid media.The coupled ISPH-TLSPH scheme is used to simulate several benchmark test cases of hydro-elastic problems.The method is validated by comparison of the presented results with experiments and numerical simulations from other researchers.展开更多
While Eulerian smoothed particle hydrodynamics(SPH)method has received increasing attention in scientific and industrial communities owing to its high spatial accuracy,it exhibits excessive numerical dissipation due t...While Eulerian smoothed particle hydrodynamics(SPH)method has received increasing attention in scientific and industrial communities owing to its high spatial accuracy,it exhibits excessive numerical dissipation due to the fact that the flux is derived in particle pair pattern.In this paper,we adopt a one-dimensional weighted essentially non-oscillatory(WENO)reconstruction to reduce the numerical dissipation and improve the overall accuracy particularly in capturing the contact discontinuity.The underlying principle is to construct a 4-point stencil along the interacting line of each particle pair and then the WENO scheme is applied to reconstruct the initial states of the Riemann problem which determines the flow flux.A set of benchmark tests for both compressible and incompressible flows are studied to investigate the accuracy,robustness and versatility of the proposed Eulerian SPH method with the WENO reconstruction(ESPH-WENO).展开更多
A numerical model was established for simulating wave impact on a horizontal deck by an improved incompressible smoothed particle hydrodynamics (ISPH). As a grid-less particle method, the ISPH method has been widely u...A numerical model was established for simulating wave impact on a horizontal deck by an improved incompressible smoothed particle hydrodynamics (ISPH). As a grid-less particle method, the ISPH method has been widely used in the free-surface hydrodynamic flows with good accuracy. The improvement includes the employment of a corrective function for enhancement of angular momentum conservation in a particle-based calculation and a new estimation method to predict the pressure on the horizontal deck. The simulation results show a good agreement with the experiment. The present numerical model can be used to study wave impact load on the horizontal deck.展开更多
An improved three-dimensional incompressible smooth particle hydrodynamics(ISPH)model is developed to simulate the impact of regular wave on a horizontal plate.The improvement is the employment of a corrective functio...An improved three-dimensional incompressible smooth particle hydrodynamics(ISPH)model is developed to simulate the impact of regular wave on a horizontal plate.The improvement is the employment of a corrective function to enhance angular momentum conservation in a particle-based calculation.And a new estimation method is proposed to predict the pressure on the horizontal plate.Then,the model simulates the variation characteristics of impact pressures generated by regular wave slamming.The main features of velocity field and pressure field near the plate are presented.The present numerical model can be used to study wave impact load on the horizontal plate.展开更多
Wave propagation on uniformly sloped beaches is a canonical coastal engineering topic that has been studied extensively in the past few decades.However,most of these studies treat beaches as solid boundaries even thou...Wave propagation on uniformly sloped beaches is a canonical coastal engineering topic that has been studied extensively in the past few decades.However,most of these studies treat beaches as solid boundaries even though they are often made of porous materials,such as sediment and vegetation.Permeable beaches struck by tsunami-like waves have not been adequately investigated.It is expected that the degree of penneability plays a crucial role in mitigating the impact of the wave.This study examines solitary wave run-ups on sandy beaches using an incompressible smoothed particle hydrodynamics(ISPH)model.The permeability of the beach is considered to be directly related to the diameter of its constituent sand particles.To obtain a satisfactory pressure field,which cannot be achieved using the original ISPH algorithm,the source term of the pressure Poisson equation has been modified based on a higher-order source-term expression.Flows within the porous medium are computed in the same framework as those outside the porous medium.In the current model,no transition zone is needed at the boundary of the porous structure.The wave-attenuation effect of the porous medium is discussed,with a particular focus on the relationship between the mn-up height and grainsize.展开更多
Free surface flows are of significant interest in Computational Fluid Dynamics（CFD）. However, violent water wave impact simulation especially when free surface breaks or impacts on solid wall can be a big challenge ...Free surface flows are of significant interest in Computational Fluid Dynamics（CFD）. However, violent water wave impact simulation especially when free surface breaks or impacts on solid wall can be a big challenge for many CFD techniques. Smoothed Particle Hydrodynamics（SPH） has been reported as a robust and reliable method for simulating violent free surface flows. Weakly compressible SPH（WCSPH） uses an equation of state with a large sound speed, and the results of the WCSPH can induce a noisy pressure field and spurious oscillation of pressure in time history for wave impact problem simulation. As a remedy, the truly incompressible SPH（ISPH） technique was introduced, which uses a pressure Poisson equation to calculate the pressure. Although the pressure distribution in the whole field obtained by ISPH is smooth, the stability of the techniques is still an open discussion. In this paper, a new free surface identification scheme and solid boundary handling method are introduced to improve the accuracy of ISPH. This modified ISPH is used to study dam breaking flow and violent tank sloshing flows. On the comparative study of WCSPH and ISPH, the accuracy and efficiency are assessed and the results are compared with the experimental data.展开更多
In this paper,a novel unconditionally energy stable Smoothed Particle Hydrodynamics(SPH)method is proposed and implemented for incompressible fluid flows.In this method,we apply operator splitting to break the momentu...In this paper,a novel unconditionally energy stable Smoothed Particle Hydrodynamics(SPH)method is proposed and implemented for incompressible fluid flows.In this method,we apply operator splitting to break the momentum equation into equations involving the non-pressure term and pressure term separately.The idea behind the splitting is to simplify the calculation while still maintaining energy stability,and the resulted algorithm,a type of improved pressure correction scheme,is both efficient and energy stable.We show in detail that energy stability is preserved at each full-time step,ensuring unconditionally numerical stability.Numerical examples are presented and compared to the analytical solutions,suggesting that the proposed method has better accuracy and stability.Moreover,we observe that if we are interested in steady-state solutions only,our method has good performance as it can achieve the steady-state solutions rapidly and accurately.展开更多
文摘The purpose of the present paper is to introduce a simple two-part multi-phase model for the sediment transport problems based on the incompressible smoothed particle hydrodynamics（ISPH） method. The proposed model simulates the movement of sediment particles in two parts. The sediment particles are classified into three categories, including the motionless particles, moving particles behave like a rigid body, and moving particles with a pseudo fluid behavior. The criterion for the classification of sediment particles is the Bingham rheological model. Verification of the present model is performed by simulation of the dam break waves on movable beds with different conditions and the bed scouring under steady flow condition. Comparison of the present model results, the experimental data and available numerical results show that it has good ability to simulate flow pattern and sediment transport.
基金Project supported by the National Natural Science Foun-dation of China(Grant Nos.11172306,U1530110)the Institu-te of Systems Engineering,China Academy of Engineering Physics(Grant No.2013KJZ01)
文摘Smoothed particle hydrodynamics （SPH） is a Lagrangian, meshfree particle method and has been widely applied to diffe- rent areas in engineering and science. Since its original extension to modeling free surface flows by Monaghan in 1994, SPH has been gradually developed into an attractive approach for modeling viscous incompressible fluid flows. This paper presents an overview on the recent progresses of SPH in modeling viscous incompressible flows in four major aspects which are closely related to the computational accuracy of SPH simulations. The advantages and disadvantages of different SPH particle approximation sche- mes, pressure field solution approaches, solid boundary treatment algorithms and particle adapting algorithms are described and analyzed. Some new perspectives and fuRtre trends in SPH modeling of viscous incompressible flows are discussed.
基金This work was supported by the National Natural Science Foundation of China under Grant Nos. 61572075 and 61702036, the National Key Research and Development Program of China under Grant Nos. 2016YFB0700502 and 2016YFB1001404, and the Fun- damental Research Funds for the Central Universities of China under Grant No. 2302017FRF-TP-17-012A1.
文摘In order to capture stable and realistic microscopic features of fluid surface, a surface tension and adhesion method based on implicit incompressible SPH （smoothed particle hydrodynamics） is presented in this paper. It gives a steady and fast tension model and can solve the problem of not considering adhesion. Molecular cohesion and surface minimization are considered for surface tension, and adhesion is added to show the microscopic characteristics of the surface. To simulate surface tension and adhesion stably and efficiently, the surface tension and adhesion model is integrated to an implicit incompressible SPH method. The experimental results show that the method can better simulate surface features in a variety of scenarios compared with previous methods and meanwhile ensure stability and efficiency.
基金Project supported by the Austrian Research Promotion Agency (Grant No. 865963)the National Natural Science Foundation of China (Grant No. 51709230).
文摘Predictive-corrective incompressible smoothed particle hydrodynamics (PCISPH) is an efficient SPH variation originally developed for computer graphics. Its application in modeling physics-focused fluid flows has not yet been reported. In this work, an improved PCISPH method is presented for physics-focused fluid flow modeling. Different from traditional weakly-compressible SPH (WCSPH) and incompressible SPH (ISPH), PCISPH satisfies the incompressibility requirement at the particle level without a predefined equation of state. The pressure is obtained using an iterative predictive-corrective scheme at each individual particle. The presented PCISPH allows much larger time steps compared with WCSPH. It also avoids the time-consuming solution of Pressure Poisson Equation (PPE) in ISPH. Consequently, the PCISPH has high computational efficiency even with millions of computational particles. To ensure physically correct modeling of fluid flows, we employ several techniques to enhance the accuracy and stability of the PCISPH:(1) the continuity equation is used to predict density, replacing the mass summation approach used in the original PCISPH,(2) numerical diffusion and pressure smoothing are introduced to improve the pressure computation,(3) a generalized boundary treatment approach which can handle arbitrarily complex geometries is employed,(4) an adaptive time-stepping algorithm is used, allowing efficient simulation as well as ensuring stability. The performance of the improved PCISPH is systematically investigated using three standard SPH validation cases. Comparisons between the improved PCISPH and the state-of-the-art 5 - SPH are presented. It is found that the improved PCISPH gives numerical results as accurate as J - SPH, except for having moderate temporal pressure oscillations. However, the numerical results show that the improved PCISPH is approximately five times faster than 8 -SPH. The improved PCISPH method shows to be a promising tool for large-scale three-dimensional fluid flow modeling.
文摘A fully Lagrangian algorithm for numerical simulation of fluid-elastic structure interaction(FSI)problems is developed based on the Smoothed Particle Hydrodynamics(SPH)method.The developed method corresponds to incompressible fluid flows and elastic structures.Divergence-free(projection based)incompressible SPH(ISPH)is used for the fluid phase,while the equations of motion for structural dynamics are solved using Total Lagrangian SPH(TLSPH)method.The temporal pressure noise can occur at the free surface and fluid-solid interfaces due to errors associated with the truncated kernels.A FSI particle shifting scheme is implemented to produce sufficiently homogeneous particle distributions to enable stable,accurate,converged solutions without noise in the pressure field.The coupled algorithm,with the addition of proposed particle shifting scheme,is able to provide the possibility of simultaneous integration of governing equations for all particles,regardless of their material type.This remedy without need for tuning a new parameter,resolves the unphysical discontinuity beneath the interface of fluid-solid media.The coupled ISPH-TLSPH scheme is used to simulate several benchmark test cases of hydro-elastic problems.The method is validated by comparison of the presented results with experiments and numerical simulations from other researchers.
基金This work was supported by the China Scholarship Council(Grant No.No.201906120035)Chi Zhang and Xiangyu Hu would like to express their gratitude to Deutsche Forschungsgemeinschaft(DFG)for their sponsorship(Grant No.DFG HU1527/12-4).
文摘While Eulerian smoothed particle hydrodynamics(SPH)method has received increasing attention in scientific and industrial communities owing to its high spatial accuracy,it exhibits excessive numerical dissipation due to the fact that the flux is derived in particle pair pattern.In this paper,we adopt a one-dimensional weighted essentially non-oscillatory(WENO)reconstruction to reduce the numerical dissipation and improve the overall accuracy particularly in capturing the contact discontinuity.The underlying principle is to construct a 4-point stencil along the interacting line of each particle pair and then the WENO scheme is applied to reconstruct the initial states of the Riemann problem which determines the flow flux.A set of benchmark tests for both compressible and incompressible flows are studied to investigate the accuracy,robustness and versatility of the proposed Eulerian SPH method with the WENO reconstruction(ESPH-WENO).
基金the National High Technology Research and Development Program of China (863 Program,Grant No.2007AA11Z130)
文摘A numerical model was established for simulating wave impact on a horizontal deck by an improved incompressible smoothed particle hydrodynamics (ISPH). As a grid-less particle method, the ISPH method has been widely used in the free-surface hydrodynamic flows with good accuracy. The improvement includes the employment of a corrective function for enhancement of angular momentum conservation in a particle-based calculation and a new estimation method to predict the pressure on the horizontal deck. The simulation results show a good agreement with the experiment. The present numerical model can be used to study wave impact load on the horizontal deck.
基金Supported by the National Science Foundation of China(51109022)the National Science Foundation of Liaoning Province(201202020)the Key Laboratory Foundation of Dalian University of Technoloty(LP12005)
文摘An improved three-dimensional incompressible smooth particle hydrodynamics(ISPH)model is developed to simulate the impact of regular wave on a horizontal plate.The improvement is the employment of a corrective function to enhance angular momentum conservation in a particle-based calculation.And a new estimation method is proposed to predict the pressure on the horizontal plate.Then,the model simulates the variation characteristics of impact pressures generated by regular wave slamming.The main features of velocity field and pressure field near the plate are presented.The present numerical model can be used to study wave impact load on the horizontal plate.
基金Supported by the Royal Academy of Engineering UK-China Urban Flooding Research Impact Programme(Grant No.UUFRIP\100051)the Ministry of Education and State Administration of Foreign Experts Affairs 111 Project(Grant No.B17015)the Cambridge Tier-2 system operated by the University of Cambridge Research Computing Service(http://www.hpc.cam.ac.uk)funded by EPSRC Tier-2 capital(Grant No.EP/P020259/1).
文摘Wave propagation on uniformly sloped beaches is a canonical coastal engineering topic that has been studied extensively in the past few decades.However,most of these studies treat beaches as solid boundaries even though they are often made of porous materials,such as sediment and vegetation.Permeable beaches struck by tsunami-like waves have not been adequately investigated.It is expected that the degree of penneability plays a crucial role in mitigating the impact of the wave.This study examines solitary wave run-ups on sandy beaches using an incompressible smoothed particle hydrodynamics(ISPH)model.The permeability of the beach is considered to be directly related to the diameter of its constituent sand particles.To obtain a satisfactory pressure field,which cannot be achieved using the original ISPH algorithm,the source term of the pressure Poisson equation has been modified based on a higher-order source-term expression.Flows within the porous medium are computed in the same framework as those outside the porous medium.In the current model,no transition zone is needed at the boundary of the porous structure.The wave-attenuation effect of the porous medium is discussed,with a particular focus on the relationship between the mn-up height and grainsize.
基金supported by the National Natural Science Foundations of China(Grant Nos.51009034 and 51279041)Fundamental Research Funds for the Central Universities(Grant Nos.HEUCDZ1202 and HEUCF120113)Pre-Research Foundation of General Armament Department of China(Grant No.9140A14020712CB01158)
文摘Free surface flows are of significant interest in Computational Fluid Dynamics（CFD）. However, violent water wave impact simulation especially when free surface breaks or impacts on solid wall can be a big challenge for many CFD techniques. Smoothed Particle Hydrodynamics（SPH） has been reported as a robust and reliable method for simulating violent free surface flows. Weakly compressible SPH（WCSPH） uses an equation of state with a large sound speed, and the results of the WCSPH can induce a noisy pressure field and spurious oscillation of pressure in time history for wave impact problem simulation. As a remedy, the truly incompressible SPH（ISPH） technique was introduced, which uses a pressure Poisson equation to calculate the pressure. Although the pressure distribution in the whole field obtained by ISPH is smooth, the stability of the techniques is still an open discussion. In this paper, a new free surface identification scheme and solid boundary handling method are introduced to improve the accuracy of ISPH. This modified ISPH is used to study dam breaking flow and violent tank sloshing flows. On the comparative study of WCSPH and ISPH, the accuracy and efficiency are assessed and the results are compared with the experimental data.
基金This work is partially supported by King Abdullah University of Science and Technology(KAUST)through the grants BAS/1/1351-01,URF/1/4074-01,and URF/1/3769-01.
文摘In this paper,a novel unconditionally energy stable Smoothed Particle Hydrodynamics(SPH)method is proposed and implemented for incompressible fluid flows.In this method,we apply operator splitting to break the momentum equation into equations involving the non-pressure term and pressure term separately.The idea behind the splitting is to simplify the calculation while still maintaining energy stability,and the resulted algorithm,a type of improved pressure correction scheme,is both efficient and energy stable.We show in detail that energy stability is preserved at each full-time step,ensuring unconditionally numerical stability.Numerical examples are presented and compared to the analytical solutions,suggesting that the proposed method has better accuracy and stability.Moreover,we observe that if we are interested in steady-state solutions only,our method has good performance as it can achieve the steady-state solutions rapidly and accurately.
