对传统直角坐标网格进行改进,根据计算机图形学对与物面相交的正方形网格进行切割,使单元与物面贴体,并能根据流场的变化对网格区域进行局部加密。结合直角坐标网格与非结构网格的特点,编写了自适应直角坐标网格的生成程序,并发展了基...对传统直角坐标网格进行改进,根据计算机图形学对与物面相交的正方形网格进行切割,使单元与物面贴体,并能根据流场的变化对网格区域进行局部加密。结合直角坐标网格与非结构网格的特点,编写了自适应直角坐标网格的生成程序,并发展了基于切割单元直角坐标网格的直接模拟蒙特卡洛(Direct simulation Monte Carlo,DSMC)方法。同时通过当地模拟分子数、动态时间步长技术优化DSMC方法,提升计算效率。数值结果表明,本方法在计算过程中使搜索效率得到大大提升,同时也保证了物面网格单元的贴体性,提高了物面附近流场的计算精度,还易于实现网格自适应。展开更多
Examines the moving mesh methods for solving one-dimensional time dependent partial differential equations. Introduction of the differential-algebraic formulations based on geometrical variables; Investigation of the ...Examines the moving mesh methods for solving one-dimensional time dependent partial differential equations. Introduction of the differential-algebraic formulations based on geometrical variables; Investigation of the well-posedness of the numerical approach; Discussion of some detailed numerical procedures.展开更多
In this paper, integrating the Yangtze Estuary with the Hangzhou Bay, a 2-D velocity field model is established. In the model, fine self-adaptive grids are employed to adapt to the complicated coastal shape. The hydro...In this paper, integrating the Yangtze Estuary with the Hangzhou Bay, a 2-D velocity field model is established. In the model, fine self-adaptive grids are employed to adapt to the complicated coastal shape. The hydrodynamic equations satisfied by two contravariant components of velocity vector and surface elevation in non-orthogonal curvilinear coordinates are used. In each momentum equation the coefficients before the two partial derivatives of surface elevation with respect to variables of alternative direction coordinates have different orders of magnitude, i. e., the derivative with the larger coefficient may play a more important role than that with the smaller one. With this advantage, the ADI scheme can be easily employed. The hydrodynamic factors include tidal current, river runoff and wind-induced current. In terms of tidal current, seven main constituents in the area are considered in the open boundaries. The verifications of surface elevation process and current velocity process in the spring tide and in the neap tide show that the model can preferably reflect current fields in the area. Through the simulation of Lagrangian residual current fields in summer and in winter, the paths of the exchange of water and sediment between the Yangtze Estuary and the Hangzhou Bay are elementarily discussed.展开更多
The multi-resolution adaptive grids method is proposed to solve the problems of inefficiency in the previous grid-based methods,and it can be used in clouds simulation as well as the interactive simulation between obj...The multi-resolution adaptive grids method is proposed to solve the problems of inefficiency in the previous grid-based methods,and it can be used in clouds simulation as well as the interactive simulation between objects and clouds.Oriented bounding box(OBB)hierarchical trees of objects are established,and the resolutions of global and local grids can be selected automatically.The motion equations of fluid dynamics are simplified.Upwind difference is applied to ensure the stability of the simulation process during the discrete process of partial differential equations.To solve the speed problem of existed phase functions,the improved phase function is applied to the illumination calculation of clouds.Experimental results show that the proposed methods can promote the simulation efficiency and meet the need for the simulation of large-scale clouds scene.Real-time rendering of clouds and the interaction between clouds and objects have been realized without preprocessing stage.展开更多
文摘对传统直角坐标网格进行改进,根据计算机图形学对与物面相交的正方形网格进行切割,使单元与物面贴体,并能根据流场的变化对网格区域进行局部加密。结合直角坐标网格与非结构网格的特点,编写了自适应直角坐标网格的生成程序,并发展了基于切割单元直角坐标网格的直接模拟蒙特卡洛(Direct simulation Monte Carlo,DSMC)方法。同时通过当地模拟分子数、动态时间步长技术优化DSMC方法,提升计算效率。数值结果表明,本方法在计算过程中使搜索效率得到大大提升,同时也保证了物面网格单元的贴体性,提高了物面附近流场的计算精度,还易于实现网格自适应。
基金This research was supported by Hong Kong Baptist University, Hong Kong Research Grants Council,Special Funds for Major State B
文摘Examines the moving mesh methods for solving one-dimensional time dependent partial differential equations. Introduction of the differential-algebraic formulations based on geometrical variables; Investigation of the well-posedness of the numerical approach; Discussion of some detailed numerical procedures.
基金National Natural Science Foundation of China under contract No.49776279National Excellent Youth Foundation of China under contract No.49825161
文摘In this paper, integrating the Yangtze Estuary with the Hangzhou Bay, a 2-D velocity field model is established. In the model, fine self-adaptive grids are employed to adapt to the complicated coastal shape. The hydrodynamic equations satisfied by two contravariant components of velocity vector and surface elevation in non-orthogonal curvilinear coordinates are used. In each momentum equation the coefficients before the two partial derivatives of surface elevation with respect to variables of alternative direction coordinates have different orders of magnitude, i. e., the derivative with the larger coefficient may play a more important role than that with the smaller one. With this advantage, the ADI scheme can be easily employed. The hydrodynamic factors include tidal current, river runoff and wind-induced current. In terms of tidal current, seven main constituents in the area are considered in the open boundaries. The verifications of surface elevation process and current velocity process in the spring tide and in the neap tide show that the model can preferably reflect current fields in the area. Through the simulation of Lagrangian residual current fields in summer and in winter, the paths of the exchange of water and sediment between the Yangtze Estuary and the Hangzhou Bay are elementarily discussed.
基金supported by the National Natural Science Foundation of China(No.61102167)
文摘The multi-resolution adaptive grids method is proposed to solve the problems of inefficiency in the previous grid-based methods,and it can be used in clouds simulation as well as the interactive simulation between objects and clouds.Oriented bounding box(OBB)hierarchical trees of objects are established,and the resolutions of global and local grids can be selected automatically.The motion equations of fluid dynamics are simplified.Upwind difference is applied to ensure the stability of the simulation process during the discrete process of partial differential equations.To solve the speed problem of existed phase functions,the improved phase function is applied to the illumination calculation of clouds.Experimental results show that the proposed methods can promote the simulation efficiency and meet the need for the simulation of large-scale clouds scene.Real-time rendering of clouds and the interaction between clouds and objects have been realized without preprocessing stage.
