本文研究的目的在于,使用分段线性PLIC(Piecewise Linear Interface Construction)方式构造界面,推导三维空间中的VOF(Volume of Fluid)算法PLIC3D,给出详尽的计算公式和过程。然后,用球形流体匀速运动作为分析PLIC3D算法的数值算例,比...本文研究的目的在于,使用分段线性PLIC(Piecewise Linear Interface Construction)方式构造界面,推导三维空间中的VOF(Volume of Fluid)算法PLIC3D,给出详尽的计算公式和过程。然后,用球形流体匀速运动作为分析PLIC3D算法的数值算例,比较了PLIC3D和分段常数PCIC(Piecewise Constant Interface Construction)构造法中DA3D(Donor-Acceptor in 3-Dimension)在三维空间计算界面的差别。结果显示PLIC3D优于DA3D,它能够更好地保持流体在平移运动中的形状,证实了PLIC方式的空间构造精度高于PCIC的结论。最后,利用PLIC3D计算自由面,模拟容器中流体泄漏问题,得到了其液面形状变化和速度场。展开更多
The PLIC/SN method that combines the second-order volume tracking method (PLIC-VOF) with the equation of surface normal (SN) vector was recently proposed (M. Sun, “Volume Tracking of Subgrid Particles,” Internationa...The PLIC/SN method that combines the second-order volume tracking method (PLIC-VOF) with the equation of surface normal (SN) vector was recently proposed (M. Sun, “Volume Tracking of Subgrid Particles,” International Journal for Numerical Methods in Fluids, Vol. 66, No. 12, 2011, pp. 1530-1554). The method is able to track the motion of a subgrid particle, but the accuracy is not as good as expected on high resolution grids for vortical flows. In this paper, a simple unsplit multidimensional advection algorithm is coupled with the equation of SN vector. The advection algorithm is formulated as the finite volume method, so that it can be used readily for both structured and unstructured grids while maintaining the exact mass conservation. The new method improves the accuracy significantly for high resolution grids. In the well-known test of the time-resolved vortex problem of T = 2, the circular interface is resolved with an accuracy better than ever using the equation of SN vector.展开更多
Investigating the wave field near structures in coastal and offshore engineering is of increasing significance. In the present study, simulation is done of the wave profile and flow field for waves propagating over su...Investigating the wave field near structures in coastal and offshore engineering is of increasing significance. In the present study, simulation is done of the wave profile and flow field for waves propagating over submerged bars, using PLIC-VOF （Pieeewise Linear Interface Construction） to trace the free surface of wave and finite difference method to solve vertical 2D Navier-Stokes （N-S） equations. A comparison of the numerical results for two kinds of submerged bars with the experimental ones shows that the PLIC-VOF model used in this study is effective and can compute the wave field precisely.展开更多
To simulate two-dimensional free-surface flows with complex boundaries directly and accurately, a novel VOF (Volume-of-fluid) method based on unstructured quadrilateral mesh is presented. Without introducing any compl...To simulate two-dimensional free-surface flows with complex boundaries directly and accurately, a novel VOF (Volume-of-fluid) method based on unstructured quadrilateral mesh is presented. Without introducing any complicated boundary treatment or artificial diffusion, this method treated curved boundaries directly by utilizing the inherent merit of unstructured mesh in fitting curves. The PLIC (Piecewise Linear Interface Calculation) method was adopted to obtain a second-order accurate linearized reconstruction approximation and the MLER (Modified Lagrangian-Eulerian Re-map) method was introduced to advect fluid volumes on unstructured mesh. Moreover, an analytical relation for the interface’s line constant vs. the volume clipped by the interface was developed so as to improve the method’s efficiency. To validate this method, a comprehensive series of large straining advection tests were performed. Numerical results provide convincing evidences for the method’s high volume conservative accuracy and second-order shape error convergence rate. Also, a dramatic improvement on computational accuracy over its unstructured triangular mesh counterpart is checked.展开更多
该文采用VOF(Volume-of-Fluid)中的PLIC(Piecewise Linear Interface Calculation)界面重构方法模拟研究了不同放置方式气泡之间的相互作用,重点分析了外围流体黏性及气泡间距对其影响。结果表明,外围流体黏性及气泡间距对气泡的融合及...该文采用VOF(Volume-of-Fluid)中的PLIC(Piecewise Linear Interface Calculation)界面重构方法模拟研究了不同放置方式气泡之间的相互作用,重点分析了外围流体黏性及气泡间距对其影响。结果表明,外围流体黏性及气泡间距对气泡的融合及上升速度都具有不同程度的影响,气泡水平放置时,泡间距较小时,气泡上升速度比单个要大。在气泡开始融合到此过程结束的同时,上升速度出现了先降低后反弹的现象,且随着雷诺数的增加速度降低开始时间滞后。展开更多
In this study, characteristics of flow field and wave propagation near submerged breakwater on a sloping bed are investigated with numerical model. The governing equations of the vertical two-dimensional model are Rey...In this study, characteristics of flow field and wave propagation near submerged breakwater on a sloping bed are investigated with numerical model. The governing equations of the vertical two-dimensional model are Reynolds Averaged Navier Stokes equations. The Reynolds stress terms are closed by a nonlinear k - ε turbulence transportation model. The free surface is traced through the PILC-VOF method. The proposed numerical model is verified with experimental results. The numerical result shows that the wave profile may become more asymmetrical when wave propagates over breakwater. When wave crest propagates over breakwater, the anticlockwise vortex may generate. On the contrary, when wave hollow propagates over breakwater, the clockwise vortex may generate. Meanwhile, the influenced zone of vortex created by wave crest is larger than that created by wave hollow. All the maximum values of the turbulent kinetic energy, turbulent dissipation and eddy viscosity occur on the top of breakwater. Both the turbulent dissipation and eddy viscosity increase as the turbulent kinetic energy increases. Wave energy may rapidly decrease near the breakwater because turbulent dissipation increases and energy in lower harmonics is transferred into higher harmonics.展开更多
In the paper, a weak coupling numerical model is developed for the study of the nonlinear dynamic interaction between water waves and permeable sandy seabed. The wave field solveris based on the VOF （Volume of Fluid...In the paper, a weak coupling numerical model is developed for the study of the nonlinear dynamic interaction between water waves and permeable sandy seabed. The wave field solveris based on the VOF （Volume of Fluid） method for continuity equation and the two-dimensional Reynolds Averaged Navier Stokes （RANS） equations with a k-ε closure. The free surface of cnoidal wave is traced through the PLIC-VOF （P/ecewise Linear/nterface Construction）. Blot＇s equations have been applied to solve the sandy seabed, and the u-p fmite dement formulations are derived by the application of the Galerkin weighted-residual procedure. The continuity of the pressure on the interface between fluid and porous medium domains is considered. Laboratory tests were performed to verify the proposed numerical model, and it is shown that the pore-water pressures and the wave heights computed by the VOF-FEM models are in good agreement with the experimental results. It is found that the proposed model is effective in predicting the seabed-nonlinear wave interaction and is able to handle the wave-breakwater-seabed interaction problem.展开更多
文摘本文研究的目的在于,使用分段线性PLIC(Piecewise Linear Interface Construction)方式构造界面,推导三维空间中的VOF(Volume of Fluid)算法PLIC3D,给出详尽的计算公式和过程。然后,用球形流体匀速运动作为分析PLIC3D算法的数值算例,比较了PLIC3D和分段常数PCIC(Piecewise Constant Interface Construction)构造法中DA3D(Donor-Acceptor in 3-Dimension)在三维空间计算界面的差别。结果显示PLIC3D优于DA3D,它能够更好地保持流体在平移运动中的形状,证实了PLIC方式的空间构造精度高于PCIC的结论。最后,利用PLIC3D计算自由面,模拟容器中流体泄漏问题,得到了其液面形状变化和速度场。
文摘The PLIC/SN method that combines the second-order volume tracking method (PLIC-VOF) with the equation of surface normal (SN) vector was recently proposed (M. Sun, “Volume Tracking of Subgrid Particles,” International Journal for Numerical Methods in Fluids, Vol. 66, No. 12, 2011, pp. 1530-1554). The method is able to track the motion of a subgrid particle, but the accuracy is not as good as expected on high resolution grids for vortical flows. In this paper, a simple unsplit multidimensional advection algorithm is coupled with the equation of SN vector. The advection algorithm is formulated as the finite volume method, so that it can be used readily for both structured and unstructured grids while maintaining the exact mass conservation. The new method improves the accuracy significantly for high resolution grids. In the well-known test of the time-resolved vortex problem of T = 2, the circular interface is resolved with an accuracy better than ever using the equation of SN vector.
文摘Investigating the wave field near structures in coastal and offshore engineering is of increasing significance. In the present study, simulation is done of the wave profile and flow field for waves propagating over submerged bars, using PLIC-VOF （Pieeewise Linear Interface Construction） to trace the free surface of wave and finite difference method to solve vertical 2D Navier-Stokes （N-S） equations. A comparison of the numerical results for two kinds of submerged bars with the experimental ones shows that the PLIC-VOF model used in this study is effective and can compute the wave field precisely.
基金the National Natural Science Foundation ofChina under Grant No. 50779043, 50779045
文摘To simulate two-dimensional free-surface flows with complex boundaries directly and accurately, a novel VOF (Volume-of-fluid) method based on unstructured quadrilateral mesh is presented. Without introducing any complicated boundary treatment or artificial diffusion, this method treated curved boundaries directly by utilizing the inherent merit of unstructured mesh in fitting curves. The PLIC (Piecewise Linear Interface Calculation) method was adopted to obtain a second-order accurate linearized reconstruction approximation and the MLER (Modified Lagrangian-Eulerian Re-map) method was introduced to advect fluid volumes on unstructured mesh. Moreover, an analytical relation for the interface’s line constant vs. the volume clipped by the interface was developed so as to improve the method’s efficiency. To validate this method, a comprehensive series of large straining advection tests were performed. Numerical results provide convincing evidences for the method’s high volume conservative accuracy and second-order shape error convergence rate. Also, a dramatic improvement on computational accuracy over its unstructured triangular mesh counterpart is checked.
文摘该文采用VOF(Volume-of-Fluid)中的PLIC(Piecewise Linear Interface Calculation)界面重构方法模拟研究了不同放置方式气泡之间的相互作用,重点分析了外围流体黏性及气泡间距对其影响。结果表明,外围流体黏性及气泡间距对气泡的融合及上升速度都具有不同程度的影响,气泡水平放置时,泡间距较小时,气泡上升速度比单个要大。在气泡开始融合到此过程结束的同时,上升速度出现了先降低后反弹的现象,且随着雷诺数的增加速度降低开始时间滞后。
基金the National Natural Science Foundation of China(Grant No.10472032,50879030,51179077)the Project Founded by Priority Academic Program Development of Jiangsu Higher Education Institutions
基金The National Natural Science Foundation of China under contract Nos 50979008 and 50909009Program for Hunan Province Key Laboratory of WaterSediment Sciences & Flood Hazard Prevention and Open Research Fund Program of State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering,Hohai University No.2008490911
文摘In this study, characteristics of flow field and wave propagation near submerged breakwater on a sloping bed are investigated with numerical model. The governing equations of the vertical two-dimensional model are Reynolds Averaged Navier Stokes equations. The Reynolds stress terms are closed by a nonlinear k - ε turbulence transportation model. The free surface is traced through the PILC-VOF method. The proposed numerical model is verified with experimental results. The numerical result shows that the wave profile may become more asymmetrical when wave propagates over breakwater. When wave crest propagates over breakwater, the anticlockwise vortex may generate. On the contrary, when wave hollow propagates over breakwater, the clockwise vortex may generate. Meanwhile, the influenced zone of vortex created by wave crest is larger than that created by wave hollow. All the maximum values of the turbulent kinetic energy, turbulent dissipation and eddy viscosity occur on the top of breakwater. Both the turbulent dissipation and eddy viscosity increase as the turbulent kinetic energy increases. Wave energy may rapidly decrease near the breakwater because turbulent dissipation increases and energy in lower harmonics is transferred into higher harmonics.
基金The study was financially supported by the National Natural Science Foundation of China(Grant Nos.10202003 and 50479015)Program for New Century Excellent Talents in University(NCET-05-0710)
文摘In the paper, a weak coupling numerical model is developed for the study of the nonlinear dynamic interaction between water waves and permeable sandy seabed. The wave field solveris based on the VOF （Volume of Fluid） method for continuity equation and the two-dimensional Reynolds Averaged Navier Stokes （RANS） equations with a k-ε closure. The free surface of cnoidal wave is traced through the PLIC-VOF （P/ecewise Linear/nterface Construction）. Blot＇s equations have been applied to solve the sandy seabed, and the u-p fmite dement formulations are derived by the application of the Galerkin weighted-residual procedure. The continuity of the pressure on the interface between fluid and porous medium domains is considered. Laboratory tests were performed to verify the proposed numerical model, and it is shown that the pore-water pressures and the wave heights computed by the VOF-FEM models are in good agreement with the experimental results. It is found that the proposed model is effective in predicting the seabed-nonlinear wave interaction and is able to handle the wave-breakwater-seabed interaction problem.
