A two-dimensional hybrid numerical model, FEM-LES-VOF, for free surface flows is proposed in this study, which is a combination of three-step Taylor-Galerkin finite element method, large eddy simulation with the Smago...A two-dimensional hybrid numerical model, FEM-LES-VOF, for free surface flows is proposed in this study, which is a combination of three-step Taylor-Galerkin finite element method, large eddy simulation with the Smagorinsky sub-grid model and Computational Lagrangian-Eulerian Advection Remap Volume of Fluid （CLEAR-VOF） method. The present FEM-LES-VOF model allows the fluid flows involving violent free surface and turbulence subject to complex boundary configuration to be simulated in a straightforward manner with unstructured grids in the context of finite element method. Numerical simulation of a benchmark problem of dam breaking is conducted to verify the present model. Comparisons with experimental data show that the proposed model works well and is capable of producing reliable predictions for free surface flows. Using the FEM-LES-VOF model, the free surface flow over a semi-circular obstruction is investigated. The simulation results are compared with available experimental and numerical results. Good performance of the FEM-LES-VOF model is demonstrated again. Moreover, the numerical studies show that the turbulence plays an important role in the evolution of free surface when the reflected wave propagates upstream during the fluid flow passing the submerged obstacle.展开更多
This paper is concerned with a mathematical model for two-dimensional strong turbulence flow with free surface including the effects of streamline curvature in orthogonal curvilinear coordinate system, with which the ...This paper is concerned with a mathematical model for two-dimensional strong turbulence flow with free surface including the effects of streamline curvature in orthogonal curvilinear coordinate system, with which the characteristics of the turbulence flow field on the ogee spillway was numerical simulated. In the numerical simulation, the flow control equations in orthogonal curvilinear coordinate system were discretized by the finite volume method, the physical parameters（ P, U,V,K,ε,γt , etc. ） were arranged on a staggered grid, the discretized equations were solved with the SIMPLEC method, and the complex free surface was dealt with VOF method. The computed results show that the velocity fields, pressure field, shear stress distribution and kinetic energy of turbulent flow on the ogee spillway are in agreement with experimental data. This confirms that the model can be used for numerieal simulation of the turbulence flow on ogee spillway.展开更多
The particle simulation method is used to solve free-surface slurry flow problems that may be encountered in several scientific and engineering fields.The main idea behind the use of the particle simulation method is ...The particle simulation method is used to solve free-surface slurry flow problems that may be encountered in several scientific and engineering fields.The main idea behind the use of the particle simulation method is to treat granular or other materials as an assembly of many particles.Compared with the continuum-mechanics-based numerical methods such as the finite element and finite volume methods,the movement of each particle is accurately described in the particle simulation method so that the free surface of a slurry flow problem can be automatically obtained.The major advantage of using the particle simulation method is that only a simple numerical algorithm is needed to solve the governing equation of a particle simulation system.For the purpose of illustrating how to use the particle simulation method to solve free-surface flow problems,three examples involving slurry flow on three different types of river beds have been considered.The related particle simulation results obtained from these three examples have demonstrated that:1) The particle simulation method is a promising and useful method for solving free-surface flow problems encountered in both the scientific and engineering fields;2) The shape and irregular roughness of a river bed can have a significant effect on the free surface morphologies of slurry flow when it passes through the river bed.展开更多
通过在界面标识方程中引入人工压缩项,采用基于非结构网格的高分辨率有界格式,编程实现了一类适合模拟复杂界面流问题的VOF(Volume of Fluid)方法.这类VOF方法可以自动处理界面的拓扑演化,无须进行实时的界面重构,提高了计算效率.应用...通过在界面标识方程中引入人工压缩项,采用基于非结构网格的高分辨率有界格式,编程实现了一类适合模拟复杂界面流问题的VOF(Volume of Fluid)方法.这类VOF方法可以自动处理界面的拓扑演化,无须进行实时的界面重构,提高了计算效率.应用这种基于有界压缩思想的界面流模拟方法,对三维Rayleigh-Taylor不稳定性问题进行了并行模拟.计算结果与相关文献的数据吻合较好,证明了算法的可靠性.研究了密度差和Reynolds数对界面演化的影响,分析了在不同Atwood数下鞍点结构演化规律的异同,对于Reynolds数小于282的界面流问题黏性起着很明显的作用,而Atwood数的影响限于低密度差的界面流动问题,即Atwood数小于0.90的情形.展开更多
应用流体体积法(Volume of Fluid,VOF)模型跟踪稳定器近水面拖动时的自由液面的变化,利用计算流体动力学软件FLUENT对线列阵稳定器近水面的阻力性能进行数值模拟,分析研究了近水面兴波对其阻力性能的影响。分别计算了在不同水深的静水...应用流体体积法(Volume of Fluid,VOF)模型跟踪稳定器近水面拖动时的自由液面的变化,利用计算流体动力学软件FLUENT对线列阵稳定器近水面的阻力性能进行数值模拟,分析研究了近水面兴波对其阻力性能的影响。分别计算了在不同水深的静水和有波浪载荷工况下近水面拖动时不同种类的线列阵稳定器的阻力大小,并将数值模拟的结果与水池实验结果进行对比。结果表明,稳定器在近水面无波和有波情况下的阻力大小均比深水域静水的阻力要大,而且在有波情况与相对浸深为0.3时的阻力性能基本相等。展开更多
基金the National Natural Science Foundation of China (Grant No. 50409015)the Program forChangjiang Scholars and Innovative Research Team inUniversity (Grant No. IRT0420) the 40th ChinaPostdoctoral Science Foundation
文摘A two-dimensional hybrid numerical model, FEM-LES-VOF, for free surface flows is proposed in this study, which is a combination of three-step Taylor-Galerkin finite element method, large eddy simulation with the Smagorinsky sub-grid model and Computational Lagrangian-Eulerian Advection Remap Volume of Fluid （CLEAR-VOF） method. The present FEM-LES-VOF model allows the fluid flows involving violent free surface and turbulence subject to complex boundary configuration to be simulated in a straightforward manner with unstructured grids in the context of finite element method. Numerical simulation of a benchmark problem of dam breaking is conducted to verify the present model. Comparisons with experimental data show that the proposed model works well and is capable of producing reliable predictions for free surface flows. Using the FEM-LES-VOF model, the free surface flow over a semi-circular obstruction is investigated. The simulation results are compared with available experimental and numerical results. Good performance of the FEM-LES-VOF model is demonstrated again. Moreover, the numerical studies show that the turbulence plays an important role in the evolution of free surface when the reflected wave propagates upstream during the fluid flow passing the submerged obstacle.
文摘This paper is concerned with a mathematical model for two-dimensional strong turbulence flow with free surface including the effects of streamline curvature in orthogonal curvilinear coordinate system, with which the characteristics of the turbulence flow field on the ogee spillway was numerical simulated. In the numerical simulation, the flow control equations in orthogonal curvilinear coordinate system were discretized by the finite volume method, the physical parameters（ P, U,V,K,ε,γt , etc. ） were arranged on a staggered grid, the discretized equations were solved with the SIMPLEC method, and the complex free surface was dealt with VOF method. The computed results show that the velocity fields, pressure field, shear stress distribution and kinetic energy of turbulent flow on the ogee spillway are in agreement with experimental data. This confirms that the model can be used for numerieal simulation of the turbulence flow on ogee spillway.
基金Project(11272359)supported by the National Natural Science Foundation of China
文摘The particle simulation method is used to solve free-surface slurry flow problems that may be encountered in several scientific and engineering fields.The main idea behind the use of the particle simulation method is to treat granular or other materials as an assembly of many particles.Compared with the continuum-mechanics-based numerical methods such as the finite element and finite volume methods,the movement of each particle is accurately described in the particle simulation method so that the free surface of a slurry flow problem can be automatically obtained.The major advantage of using the particle simulation method is that only a simple numerical algorithm is needed to solve the governing equation of a particle simulation system.For the purpose of illustrating how to use the particle simulation method to solve free-surface flow problems,three examples involving slurry flow on three different types of river beds have been considered.The related particle simulation results obtained from these three examples have demonstrated that:1) The particle simulation method is a promising and useful method for solving free-surface flow problems encountered in both the scientific and engineering fields;2) The shape and irregular roughness of a river bed can have a significant effect on the free surface morphologies of slurry flow when it passes through the river bed.
文摘通过在界面标识方程中引入人工压缩项,采用基于非结构网格的高分辨率有界格式,编程实现了一类适合模拟复杂界面流问题的VOF(Volume of Fluid)方法.这类VOF方法可以自动处理界面的拓扑演化,无须进行实时的界面重构,提高了计算效率.应用这种基于有界压缩思想的界面流模拟方法,对三维Rayleigh-Taylor不稳定性问题进行了并行模拟.计算结果与相关文献的数据吻合较好,证明了算法的可靠性.研究了密度差和Reynolds数对界面演化的影响,分析了在不同Atwood数下鞍点结构演化规律的异同,对于Reynolds数小于282的界面流问题黏性起着很明显的作用,而Atwood数的影响限于低密度差的界面流动问题,即Atwood数小于0.90的情形.
文摘应用流体体积法(Volume of Fluid,VOF)模型跟踪稳定器近水面拖动时的自由液面的变化,利用计算流体动力学软件FLUENT对线列阵稳定器近水面的阻力性能进行数值模拟,分析研究了近水面兴波对其阻力性能的影响。分别计算了在不同水深的静水和有波浪载荷工况下近水面拖动时不同种类的线列阵稳定器的阻力大小,并将数值模拟的结果与水池实验结果进行对比。结果表明,稳定器在近水面无波和有波情况下的阻力大小均比深水域静水的阻力要大,而且在有波情况与相对浸深为0.3时的阻力性能基本相等。
