In the process of deep-sea mining,the liquid-solid flows in the vertical transportation pipeline are very complex.In the present work,an in-house solver MPSDEM-SJTU based on the improved MPS and DEM is developed for t...In the process of deep-sea mining,the liquid-solid flows in the vertical transportation pipeline are very complex.In the present work,an in-house solver MPSDEM-SJTU based on the improved MPS and DEM is developed for the simulation of hydraulic conveying.Firstly,three examples including the multilayer cylinder collapse,the Poiseuille flow and two-phase dam-break are used to validate the precision of the DEM model,the pipe flow model and MPS-DEM coupling model,respectively.Then,the hydraulic conveying with coarse particles in a vertical pipe is simulated.The solid particle distribution is presented and investigated in detail.Finally,the coupling method is successfully applied for the simulation of the liquid-solid flows in a vertical pipe with rotating blades,which shows the stability of the solver under rotating boundary conditions.This fully Lagrangian model is expected to be a new approach for analyzing hydraulic conveying.展开更多
The interaction between structure and wave is a typical phenomenon in naval architecture and ocean engineering.In this paper,numerical simulation is carried out to study the interaction between a two-dimensional subme...The interaction between structure and wave is a typical phenomenon in naval architecture and ocean engineering.In this paper,numerical simulation is carried out to study the interaction between a two-dimensional submerged,fixed,horizontal rigid plate and solitary wave with our in-house meshless particle CFD solver MLParticle-SJTU.First,the in-house CFD solver is verified by experimental results conducted at the State Key Laboratory of Coastal and Offshore Engineering,Dalian University of Technology.During the verification,the plate is submerged under water and the solitary wave with a given amplitude is generated by a piston-type wave maker.Free surface elevation of the wave and the pressure impacting on the plate is recorded and compared with experimental data respectively.The predicted pressure and surface elevation agree well with the experimental results.Then in order to further investigate factors affecting wave-structure interaction,wave height,submerged depth and plate length are analyzed.展开更多
In order to account for rigid-flexible coupling effects of floating offshore wind turbines, a nonlinear rigid-flexible coupled dynamic model is proposed in this paper. The proposed nonlinear coupled model takes the hi...In order to account for rigid-flexible coupling effects of floating offshore wind turbines, a nonlinear rigid-flexible coupled dynamic model is proposed in this paper. The proposed nonlinear coupled model takes the higher-order axial displacements into account, which are usually neglected in the conventional linear dynamic model. Subsequently,investigations on the dynamic differences between the proposed nonlinear dynamic model and the linear one are conducted. The results demonstrate that the stiffness of the turbine blades in the proposed nonlinear dynamic model increases with larger overall motions but that in the linear dynamic model declines with larger overall motions.Deformation of the blades in the nonlinear dynamic model is more reasonable than that in the linear model as well.Additionally, more distinct coupling effects are observed in the proposed nonlinear model than those in the linear model. Finally, it shows that the aerodynamic loads, the structural loads and global dynamic responses of floating offshore wind turbines using the nonlinear dynamic model are slightly smaller than those using the linear dynamic model. In summary, compared with the conventional linear dynamic model, the proposed nonlinear coupling dynamic model is a higher-order dynamic model in consideration of the rigid-flexible coupling effects of floating offshore wind turbines, and accord more perfectly with the engineering facts.展开更多
In this paper, an efficient multigrid fictitious boundary method （MFBM） coupled with the FEM solver package FEATFLOW was used for the detailed simulation of incompressible viscous flows around one or more moving NAC...In this paper, an efficient multigrid fictitious boundary method （MFBM） coupled with the FEM solver package FEATFLOW was used for the detailed simulation of incompressible viscous flows around one or more moving NACA0012 airfoils. The calculations were carded on a fixed multigrid finite element mesh on which fluid equations were satisfied everywhere, and the airfoils were allowed to move freely through the mesh. The MFBM was employed to treat interactions between the fluid and the airfoils The motion of the airfoils was modeled by Newton-Euler equations. Numerical results of experiments verify that this method provides an efficient way to simulate incompressible viscous flows around moving airfoils.展开更多
A numerical simulation model based on an open source Computational Fluid Dynamics （CFD） package-Open Field Operation and Manipulation （OpenFOAM） has been developed to study highly nonlinear steady and unsteady fre...A numerical simulation model based on an open source Computational Fluid Dynamics （CFD） package-Open Field Operation and Manipulation （OpenFOAM） has been developed to study highly nonlinear steady and unsteady free surface flows. A two-fluid formulation is used in this model and the free surface is captured using the classical Volume Of Fluid （VOF） method. The incompressible Euler/Navier-Stokes equations are solved using a finite volume method on unstructured polyhedral cells. Both steady and unsteady free surface flows are simulated, which include： （1） a submerged NACA0012 2-D hydrofoil moving at a constant speed, （2） the Wigley hull moving at a constant speed, （3） numerical wave tank, （4） green water overtopping a fixed 2-D deck, （5） green water impact on a fixed 3-D body without or with a vertical wall on the deck. The numerical results obtained have been compared with the experimental measurements and other CFD results, and the agreements are satisfactory. The present numerical model can thus be used to simulate highly nonlinear steady and unsteady free surface flows.展开更多
The bow wave generated by a ship hull that advances at constant speed in calm water is considered. The bow wave only depends on the shape of the ship bow （not on the hull geometry aft of the bow wave）. This basic pr...The bow wave generated by a ship hull that advances at constant speed in calm water is considered. The bow wave only depends on the shape of the ship bow （not on the hull geometry aft of the bow wave）. This basic property makes it possible to de- termine the bow waves generated by a canonical family of ship bows defined in terms of relatively few parameters. Fast ships with fine bows generate overturning bow waves that consist of detached thin sheets of water, which are mostly steady until they hit the main free surface and undergo turbulent breaking up and diffusion. However, slow ships with blunt bows create highly unsteady and turbulent breaking bow waves. These two alternative flow regimes are due to a nonlinear constraint related to the Bernoulli relation at the free surface. Recent results about the ove^urning and breaking bow wave regimes, and the boundary that divides these two basic flow regimes, are reviewed. Questions and conjectures about the energy of breaking ship bow waves, and free-surface effects on flow circulation, are also noted.展开更多
The numerical simulation of the self-propelled motion of a fish with a pair of rigid pectoral fins is presented.A Navier-Stokes equation solver incorporating with the multi-block and overset grid method is developed t...The numerical simulation of the self-propelled motion of a fish with a pair of rigid pectoral fins is presented.A Navier-Stokes equation solver incorporating with the multi-block and overset grid method is developed to deal with the multi-body and moving body problems.The lift-based swimming mode is selected for the fin motion.In the lift-based swimming mode,the fin can generate great thrust and at the same time have no generation of lift force.It can be found when a pair of rigid pectoral fins generates the hydrodynamic moment,it may also generate a lateral force opposite to the centripetal direction,which has adverse effect on the turn motion of the fish.Furthermore,the periodic vortex structure generation and shedding,and their effects on the generation of hydrodynamic force are also demonstrated in this article.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51879159 and 52131102)the National Key Research and Development Program of China(Grant No.2019YFB1704200)。
文摘In the process of deep-sea mining,the liquid-solid flows in the vertical transportation pipeline are very complex.In the present work,an in-house solver MPSDEM-SJTU based on the improved MPS and DEM is developed for the simulation of hydraulic conveying.Firstly,three examples including the multilayer cylinder collapse,the Poiseuille flow and two-phase dam-break are used to validate the precision of the DEM model,the pipe flow model and MPS-DEM coupling model,respectively.Then,the hydraulic conveying with coarse particles in a vertical pipe is simulated.The solid particle distribution is presented and investigated in detail.Finally,the coupling method is successfully applied for the simulation of the liquid-solid flows in a vertical pipe with rotating blades,which shows the stability of the solver under rotating boundary conditions.This fully Lagrangian model is expected to be a new approach for analyzing hydraulic conveying.
基金the National Natural Science Foundation of China(Grant Nos.51909160 and 51879159)the National Key Research and Development Program of China(Grant Nos.2019YFB1704200 and 2019YFC0312400)+2 种基金Chang Jiang Scholars Program(Grant No.T2014099)Shanghai Excellent Academic Leaders Program(Grant No.17XD1402300)Innovative Special Project of Numerical Tank of Ministry of Industry and Information Technology of China(Grant No.2016-23/09).
文摘The interaction between structure and wave is a typical phenomenon in naval architecture and ocean engineering.In this paper,numerical simulation is carried out to study the interaction between a two-dimensional submerged,fixed,horizontal rigid plate and solitary wave with our in-house meshless particle CFD solver MLParticle-SJTU.First,the in-house CFD solver is verified by experimental results conducted at the State Key Laboratory of Coastal and Offshore Engineering,Dalian University of Technology.During the verification,the plate is submerged under water and the solitary wave with a given amplitude is generated by a piston-type wave maker.Free surface elevation of the wave and the pressure impacting on the plate is recorded and compared with experimental data respectively.The predicted pressure and surface elevation agree well with the experimental results.Then in order to further investigate factors affecting wave-structure interaction,wave height,submerged depth and plate length are analyzed.
基金financially supported by the Ministry of Industry and Information Technology of China(Grant No.[2016]546)
文摘In order to account for rigid-flexible coupling effects of floating offshore wind turbines, a nonlinear rigid-flexible coupled dynamic model is proposed in this paper. The proposed nonlinear coupled model takes the higher-order axial displacements into account, which are usually neglected in the conventional linear dynamic model. Subsequently,investigations on the dynamic differences between the proposed nonlinear dynamic model and the linear one are conducted. The results demonstrate that the stiffness of the turbine blades in the proposed nonlinear dynamic model increases with larger overall motions but that in the linear dynamic model declines with larger overall motions.Deformation of the blades in the nonlinear dynamic model is more reasonable than that in the linear model as well.Additionally, more distinct coupling effects are observed in the proposed nonlinear model than those in the linear model. Finally, it shows that the aerodynamic loads, the structural loads and global dynamic responses of floating offshore wind turbines using the nonlinear dynamic model are slightly smaller than those using the linear dynamic model. In summary, compared with the conventional linear dynamic model, the proposed nonlinear coupling dynamic model is a higher-order dynamic model in consideration of the rigid-flexible coupling effects of floating offshore wind turbines, and accord more perfectly with the engineering facts.
基金Supported by National 863 Plan Project of Ministry of Science and Technology of China under Grant No. 2006AA09Z354National Natural Science Foundation of China under Grant No. 10672101.
文摘In this paper, an efficient multigrid fictitious boundary method （MFBM） coupled with the FEM solver package FEATFLOW was used for the detailed simulation of incompressible viscous flows around one or more moving NACA0012 airfoils. The calculations were carded on a fixed multigrid finite element mesh on which fluid equations were satisfied everywhere, and the airfoils were allowed to move freely through the mesh. The MFBM was employed to treat interactions between the fluid and the airfoils The motion of the airfoils was modeled by Newton-Euler equations. Numerical results of experiments verify that this method provides an efficient way to simulate incompressible viscous flows around moving airfoils.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50739004, 11072154)the Foundation of State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University (Grant No. GKZD 010053-11)
文摘A numerical simulation model based on an open source Computational Fluid Dynamics （CFD） package-Open Field Operation and Manipulation （OpenFOAM） has been developed to study highly nonlinear steady and unsteady free surface flows. A two-fluid formulation is used in this model and the free surface is captured using the classical Volume Of Fluid （VOF） method. The incompressible Euler/Navier-Stokes equations are solved using a finite volume method on unstructured polyhedral cells. Both steady and unsteady free surface flows are simulated, which include： （1） a submerged NACA0012 2-D hydrofoil moving at a constant speed, （2） the Wigley hull moving at a constant speed, （3） numerical wave tank, （4） green water overtopping a fixed 2-D deck, （5） green water impact on a fixed 3-D body without or with a vertical wall on the deck. The numerical results obtained have been compared with the experimental measurements and other CFD results, and the agreements are satisfactory. The present numerical model can thus be used to simulate highly nonlinear steady and unsteady free surface flows.
文摘The bow wave generated by a ship hull that advances at constant speed in calm water is considered. The bow wave only depends on the shape of the ship bow （not on the hull geometry aft of the bow wave）. This basic property makes it possible to de- termine the bow waves generated by a canonical family of ship bows defined in terms of relatively few parameters. Fast ships with fine bows generate overturning bow waves that consist of detached thin sheets of water, which are mostly steady until they hit the main free surface and undergo turbulent breaking up and diffusion. However, slow ships with blunt bows create highly unsteady and turbulent breaking bow waves. These two alternative flow regimes are due to a nonlinear constraint related to the Bernoulli relation at the free surface. Recent results about the ove^urning and breaking bow wave regimes, and the boundary that divides these two basic flow regimes, are reviewed. Questions and conjectures about the energy of breaking ship bow waves, and free-surface effects on flow circulation, are also noted.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.50739004,11072154)the Foundation of State Key Laboratory of Ocean Engineering,Shanghai Jiao Tong University (Grant No.GKZD 010053-11)supported by the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning (Grant No.2008007)
文摘The numerical simulation of the self-propelled motion of a fish with a pair of rigid pectoral fins is presented.A Navier-Stokes equation solver incorporating with the multi-block and overset grid method is developed to deal with the multi-body and moving body problems.The lift-based swimming mode is selected for the fin motion.In the lift-based swimming mode,the fin can generate great thrust and at the same time have no generation of lift force.It can be found when a pair of rigid pectoral fins generates the hydrodynamic moment,it may also generate a lateral force opposite to the centripetal direction,which has adverse effect on the turn motion of the fish.Furthermore,the periodic vortex structure generation and shedding,and their effects on the generation of hydrodynamic force are also demonstrated in this article.
