A simple method is proposed, for incremental static analysis of a set of inter-colliding particles, simulating 2D flow. Within each step of proposed algorithm, the particles perform small displacements, proportional t...A simple method is proposed, for incremental static analysis of a set of inter-colliding particles, simulating 2D flow. Within each step of proposed algorithm, the particles perform small displacements, proportional to the out-of-balance forces, acting on them. Numerical experiments show that if the liquid is confined within boundaries of a set of inter-communicating vessels, then the proposed method converges to a final equilibrium state. This incremental static analysis approximates dynamic behavior with strong damping and can provide information, as a first approximation to 2D movement of a liquid. In the initial arrangement of particles, a rhombic element is proposed, which assures satisfactory incompressibility of the fluid. Based on the proposed algorithm, a simple and short computer program (a “pocket” program) has been developed, with only about 120 Fortran instructions. This program is first applied to an amount of liquid, contained in a single vessel. A coarse and refined discretization is tried. In final equilibrium state of liquid, the distribution on hydro-static pressure on vessel boundaries, obtained by proposed computational model, is found in satisfactory approximation with corresponding theoretical data. Then, an opening is formed, at the bottom of a vertical boundary of initial vessel, and the liquid is allowed to flow gradually to an adjacent vessel. Almost whole amount of liquid is transferred, from first to second vessel, except of few drops-particles, which remain, in equilibrium, at the bottom of initial vessel. In the final equilibrium state of liquid, in the second vessel, the free surface level of the liquid confirms that the proposed rhombing element assures a satisfactory incompressibility of the fluid.展开更多
Coupled effects on a single point mooring(SPM) system subjected to the combined action of wind,waves and current are studied in this paper. Due to the complicatedness of the sea state and the huge size of the vessel,p...Coupled effects on a single point mooring(SPM) system subjected to the combined action of wind,waves and current are studied in this paper. Due to the complicatedness of the sea state and the huge size of the vessel,physical experimental study is both time consuming and uneconomical,whereas the numerical study is cost-effective and DNV software provides powerful SESAM software in solving the issues. This paper focuses on the modeling process of the SPM system,catenary equilibrium calculation,static analysis of the vessel in three different scenarios,and dynamic response simulation of the SPM system under environmental excitations. The three scenarios in study are as follows:the SPM is under the combined function of(a) wind,waves and current,(b) wind and waves,(c) current and waves. They are so set that one can compare the contributions of different types of loads in both static and dynamic studies. Numerical study shows that wind and current are the two major factors contributing to the mooring line tension,and surge and sway are the two dominant motions of the moored vessel subjected to environmental excitations.展开更多
针对修复浮点程序中的精度缺陷的问题,从精度缺陷修复的基础理论和表达式变换方向,提出一种浮点程序精度缺陷修复方法,用以提升浮点计算的准确性。所提方法以浮点程序作为输入,首先,提出一种取样-替换-分类的方法,对特定精度的操作进行...针对修复浮点程序中的精度缺陷的问题,从精度缺陷修复的基础理论和表达式变换方向,提出一种浮点程序精度缺陷修复方法,用以提升浮点计算的准确性。所提方法以浮点程序作为输入,首先,提出一种取样-替换-分类的方法,对特定精度的操作进行筛选隔离;然后,进行函数之间的嵌入,再通过一组表达式间的转换规则以及变量间的映射方法重组表达式,生成具有更多重写可能性的表达式;其次,使用FPtool处理生成的表达式,再使用Herbie重写处理后的浮点表达式;最后,经过多次迭代生成比初始程序浮点计算精度更高的目标程序。在GSL(GNU Scientific Library)的10个函数上进行实验,实验结果表明,以误差小于1 ULP(Unit at the Last Place)的比例为指标,所提方法优化后的平均占比提升了5.20%。展开更多
Static stability analysis of the two-point mooring autonomous underwater vehicle(AUV) is presented.The mathematic model is a set of equilibrium equations describing the attitude of the AUV.The mooring lines are regard...Static stability analysis of the two-point mooring autonomous underwater vehicle(AUV) is presented.The mathematic model is a set of equilibrium equations describing the attitude of the AUV.The mooring lines are regarded as inelastic catenaries,and five degrees of freedom of AUV are considered.The stability of the system is represented by inequality conditions between several physical quantities and the corresponding limitations.We analyze stability of the prime AUV and find that the AUV has a flow-following tendency,which makes the swing angle big.The result shows that the two-point mooring AUV can remain stable under 2.5 kn ocean current speed,and it will weigh anchor when the speed is greater than 3 kn.Subsequent parametric study reveals the influence of the designing parameters on the stability.展开更多
文摘A simple method is proposed, for incremental static analysis of a set of inter-colliding particles, simulating 2D flow. Within each step of proposed algorithm, the particles perform small displacements, proportional to the out-of-balance forces, acting on them. Numerical experiments show that if the liquid is confined within boundaries of a set of inter-communicating vessels, then the proposed method converges to a final equilibrium state. This incremental static analysis approximates dynamic behavior with strong damping and can provide information, as a first approximation to 2D movement of a liquid. In the initial arrangement of particles, a rhombic element is proposed, which assures satisfactory incompressibility of the fluid. Based on the proposed algorithm, a simple and short computer program (a “pocket” program) has been developed, with only about 120 Fortran instructions. This program is first applied to an amount of liquid, contained in a single vessel. A coarse and refined discretization is tried. In final equilibrium state of liquid, the distribution on hydro-static pressure on vessel boundaries, obtained by proposed computational model, is found in satisfactory approximation with corresponding theoretical data. Then, an opening is formed, at the bottom of a vertical boundary of initial vessel, and the liquid is allowed to flow gradually to an adjacent vessel. Almost whole amount of liquid is transferred, from first to second vessel, except of few drops-particles, which remain, in equilibrium, at the bottom of initial vessel. In the final equilibrium state of liquid, in the second vessel, the free surface level of the liquid confirms that the proposed rhombing element assures a satisfactory incompressibility of the fluid.
基金This work has been financially supported by the Cultivation Fund of the Key Scientific and Technical Innovation Project,Ministry of Education of China under Grant No.704031by the Natural Science Foundation of Qingdao,Grant No.05-2-JC-88.
文摘Coupled effects on a single point mooring(SPM) system subjected to the combined action of wind,waves and current are studied in this paper. Due to the complicatedness of the sea state and the huge size of the vessel,physical experimental study is both time consuming and uneconomical,whereas the numerical study is cost-effective and DNV software provides powerful SESAM software in solving the issues. This paper focuses on the modeling process of the SPM system,catenary equilibrium calculation,static analysis of the vessel in three different scenarios,and dynamic response simulation of the SPM system under environmental excitations. The three scenarios in study are as follows:the SPM is under the combined function of(a) wind,waves and current,(b) wind and waves,(c) current and waves. They are so set that one can compare the contributions of different types of loads in both static and dynamic studies. Numerical study shows that wind and current are the two major factors contributing to the mooring line tension,and surge and sway are the two dominant motions of the moored vessel subjected to environmental excitations.
文摘针对修复浮点程序中的精度缺陷的问题,从精度缺陷修复的基础理论和表达式变换方向,提出一种浮点程序精度缺陷修复方法,用以提升浮点计算的准确性。所提方法以浮点程序作为输入,首先,提出一种取样-替换-分类的方法,对特定精度的操作进行筛选隔离;然后,进行函数之间的嵌入,再通过一组表达式间的转换规则以及变量间的映射方法重组表达式,生成具有更多重写可能性的表达式;其次,使用FPtool处理生成的表达式,再使用Herbie重写处理后的浮点表达式;最后,经过多次迭代生成比初始程序浮点计算精度更高的目标程序。在GSL(GNU Scientific Library)的10个函数上进行实验,实验结果表明,以误差小于1 ULP(Unit at the Last Place)的比例为指标,所提方法优化后的平均占比提升了5.20%。
基金the National Natural Science Foundation of China(No.11302176)the Special Research Fund for the Doctoral Program of Higher Education of China(No.20126102120021)
文摘Static stability analysis of the two-point mooring autonomous underwater vehicle(AUV) is presented.The mathematic model is a set of equilibrium equations describing the attitude of the AUV.The mooring lines are regarded as inelastic catenaries,and five degrees of freedom of AUV are considered.The stability of the system is represented by inequality conditions between several physical quantities and the corresponding limitations.We analyze stability of the prime AUV and find that the AUV has a flow-following tendency,which makes the swing angle big.The result shows that the two-point mooring AUV can remain stable under 2.5 kn ocean current speed,and it will weigh anchor when the speed is greater than 3 kn.Subsequent parametric study reveals the influence of the designing parameters on the stability.
