In comparison to discrete descriptions of fracture process,the recently proposed phase field methodology averts the numerical tracking strategy of discontinuities in solids,which enables the numerical implement simpli...In comparison to discrete descriptions of fracture process,the recently proposed phase field methodology averts the numerical tracking strategy of discontinuities in solids,which enables the numerical implement simplification.An implicit finite element formulation based on the diffuse phase field is extended for stable and efficient analysis of complex dynamic fracture process in ductile solids.This exhibited formulation is shown to capture entire range of the characteristics of ductile material presenting J2-plasticity,embracing plasticization,cracks initiation,propagation,branching and merging while fulfilling the basic principle of thermodynamics.Herein,we implement a staggered time integration scheme of the dynamic elasto-plastic phase field method into the commercial finite element code.The numerical performance of the present advanced phase field model has been examined through several classic dynamic fracture benchmarks,and in all cases simulation results are in good agreement with the associated experimental data and other numerical results in previous literature.展开更多
The dynamical-wave routing model of the urban unsteady and non-pressure rain pipe flow was established by conservation of mass, momentum and energy, and it was solved by applying the four point implicit difference met...The dynamical-wave routing model of the urban unsteady and non-pressure rain pipe flow was established by conservation of mass, momentum and energy, and it was solved by applying the four point implicit difference method and the pursuit method. It was obtained from the experiment checking and comparative analysis that the dynamical-wave muting model can reflect influence like attenuate and backwater when flood peak propagate in pipeline with high calculation precision and vast application scope, and it can be applied in routing of urban rain pipe flow of different slopes and inflow conditions. The routing model supplies a scientific foundation for the town rainfall piping design or checking, disaster administration of storm runoff, and so on.展开更多
A memory reduction technique is proposed for solving stationary kinetic model equations. As implied by an integral solution of the stationary kinetic equation, a velocity distribution function can be reconstructed fro...A memory reduction technique is proposed for solving stationary kinetic model equations. As implied by an integral solution of the stationary kinetic equation, a velocity distribution function can be reconstructed from given macroscopic variables. Based on this fact, we propose a technique to reconstruct distribution function at discrete level, and employ it to develop an implicit numerical method for kinetic equations. The new implicit method only stores the macroscopic quantities which appear in the collision term, and does not store the distribution functions. As a result, enormous memory requirement for solving kinetic equations is totally relieved. Several boundary conditions, such as, inlet, outlet and isothermal boundaries, are discussed. Some numerical tests demonstrate the validity and efficiency of the technique.The new implicit solver provides nearly identical solution as the explicit kinetic solver, while the memory requirement is on the same order as the Navier–Stokes solver.展开更多
基金supported by the Na⁃tional Natural Science Foundation of China(No.12302176).
文摘In comparison to discrete descriptions of fracture process,the recently proposed phase field methodology averts the numerical tracking strategy of discontinuities in solids,which enables the numerical implement simplification.An implicit finite element formulation based on the diffuse phase field is extended for stable and efficient analysis of complex dynamic fracture process in ductile solids.This exhibited formulation is shown to capture entire range of the characteristics of ductile material presenting J2-plasticity,embracing plasticization,cracks initiation,propagation,branching and merging while fulfilling the basic principle of thermodynamics.Herein,we implement a staggered time integration scheme of the dynamic elasto-plastic phase field method into the commercial finite element code.The numerical performance of the present advanced phase field model has been examined through several classic dynamic fracture benchmarks,and in all cases simulation results are in good agreement with the associated experimental data and other numerical results in previous literature.
基金Hunan Provincial Education Department of Key Projects(No.08A019)Funded Projects in Hunan Science and Technology Department(No.2008SK4029)
文摘The dynamical-wave routing model of the urban unsteady and non-pressure rain pipe flow was established by conservation of mass, momentum and energy, and it was solved by applying the four point implicit difference method and the pursuit method. It was obtained from the experiment checking and comparative analysis that the dynamical-wave muting model can reflect influence like attenuate and backwater when flood peak propagate in pipeline with high calculation precision and vast application scope, and it can be applied in routing of urban rain pipe flow of different slopes and inflow conditions. The routing model supplies a scientific foundation for the town rainfall piping design or checking, disaster administration of storm runoff, and so on.
基金supported by the National Natural Science Foundation of China(11602091 and 91530319)the National Key Research and Development Plan(2016YFB0600805)
文摘A memory reduction technique is proposed for solving stationary kinetic model equations. As implied by an integral solution of the stationary kinetic equation, a velocity distribution function can be reconstructed from given macroscopic variables. Based on this fact, we propose a technique to reconstruct distribution function at discrete level, and employ it to develop an implicit numerical method for kinetic equations. The new implicit method only stores the macroscopic quantities which appear in the collision term, and does not store the distribution functions. As a result, enormous memory requirement for solving kinetic equations is totally relieved. Several boundary conditions, such as, inlet, outlet and isothermal boundaries, are discussed. Some numerical tests demonstrate the validity and efficiency of the technique.The new implicit solver provides nearly identical solution as the explicit kinetic solver, while the memory requirement is on the same order as the Navier–Stokes solver.
