The consolidation of soft foundations is a problem that commonly appears in harbor construction engineering on muddy coasts. Introduced in this paper is the experimental study on underwater explosion treatment of soft...The consolidation of soft foundations is a problem that commonly appears in harbor construction engineering on muddy coasts. Introduced in this paper is the experimental study on underwater explosion treatment of soft foundations, including the regulation of explosion hollow development and medium movement, the law of similarity of densification and settlement of filled stone mass by shock wave pressure and explosion energy and their construction technologies, etc. A number of projects have been completed by applying this new technique, and the technique itself has been proved practicable.展开更多
The problem is solved by use of the boundary integral equation method and the high order finite element discretization on the assumption that the flow of water is inviscid, incompressible and irrotational, and the bub...The problem is solved by use of the boundary integral equation method and the high order finite element discretization on the assumption that the flow of water is inviscid, incompressible and irrotational, and the bubble gas obeys the isoentropic rule. The evolution of bubble is simulated by means of mixed Euler-Lagrangian method. The comparison of the numerical results with the 'exact solution' of a spheric bub ble and experimental data shows that the mathematical model is reasonable and the 3-D numerical method has high accuracy. Important behaviour of bubble, such as immigration and jetting, and dynamic load on an ellipsoid near explosion are derived.展开更多
Despite the non-contact underwater explosion phenomena(UNDEX)have been studied for decades and several numerical methods have been proposed in literature,its effects on military structures,especially composite ones,ar...Despite the non-contact underwater explosion phenomena(UNDEX)have been studied for decades and several numerical methods have been proposed in literature,its effects on military structures,especially composite ones,are even nowadays matter of research.In early design phases,it is not always possible to verify the shock resistance of hull structures modelling the whole phenomenon,in which fluid,gas and solid properties must be properly set in a fully coupled fluid-structure interaction(FSI)numerical model.These ones are extremely complex to set,computationally demanding and certainly not suitable for everyday design practice.In this paper,a simplified finite element(FE)model,easy to use in an early design phase,is proposed.Both,the structure and the fluid are simulated.In this approximation,the fluid behaviour is simplified,using special finite elements,available in a commercial software environment.This choice reduces the computational time and numerical efforts avoiding the problem of combining computational fluid dynamics(CFD)and FE domains and equations in a fully coupled fluid-structure interaction model.A typical parallel body block of a minesweeper is modelled,using two-dimensional multi-layered shell elements to properly account for the composite materials behaviour.For the fluid instead,three dimensional volumetric elements,directly coupled to the structural elements,are placed.In addition,the same calculation is performed,modelling separately fluid in the CFD environment and structures in the finite element one.Thus,realizing a fully coupled fluid-structure interaction model.The results obtained by applying both numerical models are compared with the structural response measured on board of a composite ship during a full-scale shock test.The simplified proposed procedure provides results in satisfactory agreement with experiments,allowing the validation of the model.Approximations are discussed and differences with the real phenomenon and fully coupled CFD+FE method are shown,providing a better understan展开更多
文摘The consolidation of soft foundations is a problem that commonly appears in harbor construction engineering on muddy coasts. Introduced in this paper is the experimental study on underwater explosion treatment of soft foundations, including the regulation of explosion hollow development and medium movement, the law of similarity of densification and settlement of filled stone mass by shock wave pressure and explosion energy and their construction technologies, etc. A number of projects have been completed by applying this new technique, and the technique itself has been proved practicable.
文摘The problem is solved by use of the boundary integral equation method and the high order finite element discretization on the assumption that the flow of water is inviscid, incompressible and irrotational, and the bubble gas obeys the isoentropic rule. The evolution of bubble is simulated by means of mixed Euler-Lagrangian method. The comparison of the numerical results with the 'exact solution' of a spheric bub ble and experimental data shows that the mathematical model is reasonable and the 3-D numerical method has high accuracy. Important behaviour of bubble, such as immigration and jetting, and dynamic load on an ellipsoid near explosion are derived.
文摘Despite the non-contact underwater explosion phenomena(UNDEX)have been studied for decades and several numerical methods have been proposed in literature,its effects on military structures,especially composite ones,are even nowadays matter of research.In early design phases,it is not always possible to verify the shock resistance of hull structures modelling the whole phenomenon,in which fluid,gas and solid properties must be properly set in a fully coupled fluid-structure interaction(FSI)numerical model.These ones are extremely complex to set,computationally demanding and certainly not suitable for everyday design practice.In this paper,a simplified finite element(FE)model,easy to use in an early design phase,is proposed.Both,the structure and the fluid are simulated.In this approximation,the fluid behaviour is simplified,using special finite elements,available in a commercial software environment.This choice reduces the computational time and numerical efforts avoiding the problem of combining computational fluid dynamics(CFD)and FE domains and equations in a fully coupled fluid-structure interaction model.A typical parallel body block of a minesweeper is modelled,using two-dimensional multi-layered shell elements to properly account for the composite materials behaviour.For the fluid instead,three dimensional volumetric elements,directly coupled to the structural elements,are placed.In addition,the same calculation is performed,modelling separately fluid in the CFD environment and structures in the finite element one.Thus,realizing a fully coupled fluid-structure interaction model.The results obtained by applying both numerical models are compared with the structural response measured on board of a composite ship during a full-scale shock test.The simplified proposed procedure provides results in satisfactory agreement with experiments,allowing the validation of the model.Approximations are discussed and differences with the real phenomenon and fully coupled CFD+FE method are shown,providing a better understan
