In this paper,a new fast and efficient algorithm,Chebyshev super spectral viscosity(SSV)method,is introduced to solve the water hammer equations.Compared with standard spectral method,the method's advantage essent...In this paper,a new fast and efficient algorithm,Chebyshev super spectral viscosity(SSV)method,is introduced to solve the water hammer equations.Compared with standard spectral method,the method's advantage essentially consists in adding a super spectral viscosity to the equations for the high wave numbers of the numerical solution.It can stabilize the numerical oscillation(Gibbs phenomenon)and improve the computational efficiency while discontinuities appear in the solution.Results obtained from the Chebyshev super spectral viscosity method exhibit greater consistency with conventional water hammer calculations.It shows that this new numerical method offers an altemative way to investigate the behavior of the water hammer in propellant pipelines.展开更多
Condensation induced water hammer is one kind of water hammer caused by cavity collapse, which occurs frequently in engineering pipelines and can bring about enormous damage. Due to the vapor condensation, the form...Condensation induced water hammer is one kind of water hammer caused by cavity collapse, which occurs frequently in engineering pipelines and can bring about enormous damage. Due to the vapor condensation, the formation and collapse of cavity are transient and of two phase character. In order to simulate the process of cavity formation and collapse, a physical model is suggested. In the model, the cavity boundary is treated as free surface of a calculating field. A numerical solution of the Navier Stokes equation is obtained by using a modified VOF (volume of fluid) method, in which the vapor condensation is considered. With the method, formation and collapse of the cavity are described, and the highest pressure is acquired. The numerical simulation results coincide with experimental results.展开更多
The water temperature stratification in large reservoirs might have serious ecological and environmental consequences. The modeling of the temperature distribution and its history is of great importance both for study...The water temperature stratification in large reservoirs might have serious ecological and environmental consequences. The modeling of the temperature distribution and its history is of great importance both for studying the underlying mechanisms and for controlling the adverse effects. To develop an effective and efficient method for simulation of temporal and spatial temperature variations, a lattice Boltzmann method（LBM） model for 3-D thermal buoyancy flows is proposed and validated by the temperature data measured in a model reservoir. This paper discusses important aspects of the LBM and its turbulence model, analyzes the gravity sinking mechanism of cold currents, and demonstrates the complexity of the temperature redistribution process. Good agreement between the simulated and measured results shows that the newly developed method is feasible and powerful, and it will be used for the water temperature prediction in actual reservoirs in a near future.展开更多
文摘In this paper,a new fast and efficient algorithm,Chebyshev super spectral viscosity(SSV)method,is introduced to solve the water hammer equations.Compared with standard spectral method,the method's advantage essentially consists in adding a super spectral viscosity to the equations for the high wave numbers of the numerical solution.It can stabilize the numerical oscillation(Gibbs phenomenon)and improve the computational efficiency while discontinuities appear in the solution.Results obtained from the Chebyshev super spectral viscosity method exhibit greater consistency with conventional water hammer calculations.It shows that this new numerical method offers an altemative way to investigate the behavior of the water hammer in propellant pipelines.
文摘Condensation induced water hammer is one kind of water hammer caused by cavity collapse, which occurs frequently in engineering pipelines and can bring about enormous damage. Due to the vapor condensation, the formation and collapse of cavity are transient and of two phase character. In order to simulate the process of cavity formation and collapse, a physical model is suggested. In the model, the cavity boundary is treated as free surface of a calculating field. A numerical solution of the Navier Stokes equation is obtained by using a modified VOF (volume of fluid) method, in which the vapor condensation is considered. With the method, formation and collapse of the cavity are described, and the highest pressure is acquired. The numerical simulation results coincide with experimental results.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10572106,10872153 and 11172219)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20130141110013)
文摘The water temperature stratification in large reservoirs might have serious ecological and environmental consequences. The modeling of the temperature distribution and its history is of great importance both for studying the underlying mechanisms and for controlling the adverse effects. To develop an effective and efficient method for simulation of temporal and spatial temperature variations, a lattice Boltzmann method（LBM） model for 3-D thermal buoyancy flows is proposed and validated by the temperature data measured in a model reservoir. This paper discusses important aspects of the LBM and its turbulence model, analyzes the gravity sinking mechanism of cold currents, and demonstrates the complexity of the temperature redistribution process. Good agreement between the simulated and measured results shows that the newly developed method is feasible and powerful, and it will be used for the water temperature prediction in actual reservoirs in a near future.
