Up to now, there are no satisfactory numerical methods for simulating wave resistance of trimarans, mainly due to the difficulty related with the strong nonlinear features of the piece hull wave making and their inter...Up to now, there are no satisfactory numerical methods for simulating wave resistance of trimarans, mainly due to the difficulty related with the strong nonlinear features of the piece hull wave making and their interference. This article proposes a numerical method for quick and effective calculation of wave resistance of trimarans to be used in engineering applications. Based on Wyatt＇s work, the nonlinear free surface boundary condition, the time domain concept, and the full nonlinear wave making theory, using the Rankine source Green function, the 3-D surface panel method is expanded to solve the trimaran wave making problems, with high order nonlinear factors being taken into account, such as the influence of the sinking and trim, transom, and ship wave immersed hull surface. And the software is successfully developed to implement the method, which is validated. Several trimaran models, including a practical trimaran with a sonar dome and the transom, are used as numerical calculation samples, their wave making resistance is calculated both by the present method and some other methods such as linear （Dawson） methods. Moreover, sample model resistance tests were carried out to provide data for comparison, validation and analysis. Through the validation by model experiments, it is concluded that present method can well predict the wave making resistance, sinking and trim, and the accuracy of wave making resistance calculation is significantly improved by taking the trim and sinking into account, especially at high speeds.展开更多
A method is presented to calculate the resistance of a high-speed displacement ship taking the effect of sinkage and trim and viscosity of fluid into account.A free surface flow field is evaluated by solving Reynolds ...A method is presented to calculate the resistance of a high-speed displacement ship taking the effect of sinkage and trim and viscosity of fluid into account.A free surface flow field is evaluated by solving Reynolds averaged Navier-Stokes(RANS) equations with volume of fluid(VoF) method.The sinkage and trim are computed by equating the vertical force and pitching moment to the hydrostatic restoring force and moment.The software Fluent,Maxsurf and MATLAB are used to implement this method.With dynamic mesh being used,the position of a ship is updated by the motion of "ship plus boundary layer" grid zone.The hull factors are introduced for fast calculating the running attitude of a ship.The method has been applied to the ship model INSEAN2340 for different Froude numbers and is found to be efficient for evaluating the flow field,resistance,sinkage and trim.展开更多
Environmental issues and rising fuel prices necessitate better energy-etlicwncy in all sectors, The shipping industry is one of the major stakeholders, responsible for 3% of global CO2 emissions, 14%-15% of global NOx...Environmental issues and rising fuel prices necessitate better energy-etlicwncy in all sectors, The shipping industry is one of the major stakeholders, responsible for 3% of global CO2 emissions, 14%-15% of global NOx emissions, and 16% of global SOx emissions. In addition, continuously rising fuel prices are also an incentive to focus on new ways for better energy-effectiveness. The green ship concept requires exploring and implementing technology on ships to increase energy-efficiency and reduce emissions. Ship operation is an important topic with large potential to increase cost-and-energy-effectiveness. This paper provided a comprehensive review of basic concepts, principles, and potential of operational options for green ships. The key challenges pertaining to ship crew i.e. academic qualifications prior to induction, in-service training and motivation were discussed. The author also deliberated on remedies to these challenges.展开更多
根据散货船特点探讨了一种面向工程应用的船舶自由浮态计算简化方法.在矩阵法的基础上,将7个水线面要素简化到4个,简化雅克比矩阵求解.采用全选主元高斯消去法求解线性方程组,以船舶浮态平衡方程组作为迭代终止条件,保证计算精度.以散货...根据散货船特点探讨了一种面向工程应用的船舶自由浮态计算简化方法.在矩阵法的基础上,将7个水线面要素简化到4个,简化雅克比矩阵求解.采用全选主元高斯消去法求解线性方程组,以船舶浮态平衡方程组作为迭代终止条件,保证计算精度.以散货船"DOLCE VITA"及"RUI AN CHENG"为例进行了实例计算,对20个压载舱进行了20万次随机装载实验,验证了算法在有横倾下的收敛性和稳定性;对5个货舱进行了20万次随机装载实验,验证了算法在有纵倾下的收敛性和稳定性;对典型载况进行计算,和装载手册给定值相比,吃水差误差都在0.01m以下.结果表明:该算法只需计算任意倾斜水线面下的排水体积和浮心坐标,计算量较小,程序实现简单,实时性、鲁棒性较好,具有一定的工程实用价值.展开更多
The shipping industry is one of the biggest industries throughout the ages. Maritime transport plays a vital role in world economy; whereas competition between maritime companies is fierce [1], at the same time agreem...The shipping industry is one of the biggest industries throughout the ages. Maritime transport plays a vital role in world economy; whereas competition between maritime companies is fierce [1], at the same time agreements of co-operation have taken different forms including alliances and mergers between companies to increase their market share. But competitions still stand despite all alliances even in same market. This intense competition drives companies to attain high level of competitiveness, by monitoring ship＇s operating performance and operating cost, emphasis on improving performance and reduce cost. On other hand new environmental regulations come to light, expansion of ECA （emission control areas）, which lead to significant higher fuel cost when using low sulfur fuel. Since the fuel cost is the largest portion of the operating cost of the vessel, a saving in fuel usage can result in considerable saving in operational costs. Furthermore, fuel saving has environmental benefits in the reduction of greenhouse gas emissions. The aim of this paper is to investigate the role of trim optimization which considers one of the easiest and cheapest methods for ship performance optimization and fuel consumption reduction trim optimization.展开更多
A practical numerical tool is developed to evaluate ship waves of high speed displacement ships on the basis of potential flow theory, in which high order boundary element method (HOBEM) based on biquadratic shape fun...A practical numerical tool is developed to evaluate ship waves of high speed displacement ships on the basis of potential flow theory, in which high order boundary element method (HOBEM) based on biquadratic shape functions is applied to solve the boundary value problem. Since the sinkage and trim of ship at high speeds are notable, influences of ship attitude on wave drag are investigated and three kinds of models are used to evaluate them. To make the numerical approach highly efficient, an incomplete LU factorization preconditioner is adopted and incorporated with the restarted generalized minimal residual method GMRES (m) to solve the boundary integral equation. A corresponding Fortran code is developed and applied to evaluate ship waves of the Wigley hull and 4a model, a transom stem ship. Computations are performed for both monohulls and catamarans over a wide range of Froude numbers (Fr= 0.10-l.00). Numerical issues including mesh convergence and computational efficiency are investigated at first. Computed results of the wave drag, sinkage and trim show generally good agreement with experimental data. Reasonable wave patterns are obtained and physical phenomena that wake angle max, where the largest waves occur, would become narrow at high speeds is also captured by the present computations. Numerical results indicate the proposed method would be accurate and efficient to evaluate resistance for hull design of high speed displacement ship.展开更多
Centrifugal forces are commonly created when ships turn, which may cause a ship to capsize in a critical situation. A mathematical model has been developed to optimize the stability coefficients for ship, with the aim...Centrifugal forces are commonly created when ships turn, which may cause a ship to capsize in a critical situation. A mathematical model has been developed to optimize the stability coefficients for ship, with the aim to prevent capsizing and to increase ship maneuverability in high-speed water craft. This model can be used to develop algorithms for control system improvement. The mathematical model presented in this paper optimized the use of multipurpose hydrofoils to reduce heeling and the trimming moment, maintaining an upright ship’s position and lessening the resistance via transverse force. Conventionally, the trimming and heeling of a ship are controlled using ballast water;however, under variable sea conditions it is sometimes difficult to control a ship’s motion using ballast water. In this case, a hydrofoil would be more stable and maneuverable than a ballast tank controlled vessel. A movable hydrofoil could theoretically be adapted from moveable aerofoil technology. This study proves the merit of further investigation into this possibility.展开更多
基金Project supported by the National Defense Science Foundation Program (Grant No. 9140A14070306JB1114)
文摘Up to now, there are no satisfactory numerical methods for simulating wave resistance of trimarans, mainly due to the difficulty related with the strong nonlinear features of the piece hull wave making and their interference. This article proposes a numerical method for quick and effective calculation of wave resistance of trimarans to be used in engineering applications. Based on Wyatt＇s work, the nonlinear free surface boundary condition, the time domain concept, and the full nonlinear wave making theory, using the Rankine source Green function, the 3-D surface panel method is expanded to solve the trimaran wave making problems, with high order nonlinear factors being taken into account, such as the influence of the sinking and trim, transom, and ship wave immersed hull surface. And the software is successfully developed to implement the method, which is validated. Several trimaran models, including a practical trimaran with a sonar dome and the transom, are used as numerical calculation samples, their wave making resistance is calculated both by the present method and some other methods such as linear （Dawson） methods. Moreover, sample model resistance tests were carried out to provide data for comparison, validation and analysis. Through the validation by model experiments, it is concluded that present method can well predict the wave making resistance, sinking and trim, and the accuracy of wave making resistance calculation is significantly improved by taking the trim and sinking into account, especially at high speeds.
基金the National Natural Science Foundation of China (No.50879090)the Advanced Research Program of GAD of the P.L.A (No.7131005)
文摘A method is presented to calculate the resistance of a high-speed displacement ship taking the effect of sinkage and trim and viscosity of fluid into account.A free surface flow field is evaluated by solving Reynolds averaged Navier-Stokes(RANS) equations with volume of fluid(VoF) method.The sinkage and trim are computed by equating the vertical force and pitching moment to the hydrostatic restoring force and moment.The software Fluent,Maxsurf and MATLAB are used to implement this method.With dynamic mesh being used,the position of a ship is updated by the motion of "ship plus boundary layer" grid zone.The hull factors are introduced for fast calculating the running attitude of a ship.The method has been applied to the ship model INSEAN2340 for different Froude numbers and is found to be efficient for evaluating the flow field,resistance,sinkage and trim.
基金Foundation item： Supported by the National Natural Science Foundation of China under Grant No.51079032, and the Excellent Youth Foundation of Heilongjiang Province of China.
文摘Environmental issues and rising fuel prices necessitate better energy-etlicwncy in all sectors, The shipping industry is one of the major stakeholders, responsible for 3% of global CO2 emissions, 14%-15% of global NOx emissions, and 16% of global SOx emissions. In addition, continuously rising fuel prices are also an incentive to focus on new ways for better energy-effectiveness. The green ship concept requires exploring and implementing technology on ships to increase energy-efficiency and reduce emissions. Ship operation is an important topic with large potential to increase cost-and-energy-effectiveness. This paper provided a comprehensive review of basic concepts, principles, and potential of operational options for green ships. The key challenges pertaining to ship crew i.e. academic qualifications prior to induction, in-service training and motivation were discussed. The author also deliberated on remedies to these challenges.
文摘根据散货船特点探讨了一种面向工程应用的船舶自由浮态计算简化方法.在矩阵法的基础上,将7个水线面要素简化到4个,简化雅克比矩阵求解.采用全选主元高斯消去法求解线性方程组,以船舶浮态平衡方程组作为迭代终止条件,保证计算精度.以散货船"DOLCE VITA"及"RUI AN CHENG"为例进行了实例计算,对20个压载舱进行了20万次随机装载实验,验证了算法在有横倾下的收敛性和稳定性;对5个货舱进行了20万次随机装载实验,验证了算法在有纵倾下的收敛性和稳定性;对典型载况进行计算,和装载手册给定值相比,吃水差误差都在0.01m以下.结果表明:该算法只需计算任意倾斜水线面下的排水体积和浮心坐标,计算量较小,程序实现简单,实时性、鲁棒性较好,具有一定的工程实用价值.
文摘The shipping industry is one of the biggest industries throughout the ages. Maritime transport plays a vital role in world economy; whereas competition between maritime companies is fierce [1], at the same time agreements of co-operation have taken different forms including alliances and mergers between companies to increase their market share. But competitions still stand despite all alliances even in same market. This intense competition drives companies to attain high level of competitiveness, by monitoring ship＇s operating performance and operating cost, emphasis on improving performance and reduce cost. On other hand new environmental regulations come to light, expansion of ECA （emission control areas）, which lead to significant higher fuel cost when using low sulfur fuel. Since the fuel cost is the largest portion of the operating cost of the vessel, a saving in fuel usage can result in considerable saving in operational costs. Furthermore, fuel saving has environmental benefits in the reduction of greenhouse gas emissions. The aim of this paper is to investigate the role of trim optimization which considers one of the easiest and cheapest methods for ship performance optimization and fuel consumption reduction trim optimization.
基金National Natural Science Foundation of China(Grant Nos.51479117,51579147)the National Key Basic Research Development Program of China(973 Program,Grant No.2014CB046203).
文摘A practical numerical tool is developed to evaluate ship waves of high speed displacement ships on the basis of potential flow theory, in which high order boundary element method (HOBEM) based on biquadratic shape functions is applied to solve the boundary value problem. Since the sinkage and trim of ship at high speeds are notable, influences of ship attitude on wave drag are investigated and three kinds of models are used to evaluate them. To make the numerical approach highly efficient, an incomplete LU factorization preconditioner is adopted and incorporated with the restarted generalized minimal residual method GMRES (m) to solve the boundary integral equation. A corresponding Fortran code is developed and applied to evaluate ship waves of the Wigley hull and 4a model, a transom stem ship. Computations are performed for both monohulls and catamarans over a wide range of Froude numbers (Fr= 0.10-l.00). Numerical issues including mesh convergence and computational efficiency are investigated at first. Computed results of the wave drag, sinkage and trim show generally good agreement with experimental data. Reasonable wave patterns are obtained and physical phenomena that wake angle max, where the largest waves occur, would become narrow at high speeds is also captured by the present computations. Numerical results indicate the proposed method would be accurate and efficient to evaluate resistance for hull design of high speed displacement ship.
文摘Centrifugal forces are commonly created when ships turn, which may cause a ship to capsize in a critical situation. A mathematical model has been developed to optimize the stability coefficients for ship, with the aim to prevent capsizing and to increase ship maneuverability in high-speed water craft. This model can be used to develop algorithms for control system improvement. The mathematical model presented in this paper optimized the use of multipurpose hydrofoils to reduce heeling and the trimming moment, maintaining an upright ship’s position and lessening the resistance via transverse force. Conventionally, the trimming and heeling of a ship are controlled using ballast water;however, under variable sea conditions it is sometimes difficult to control a ship’s motion using ballast water. In this case, a hydrofoil would be more stable and maneuverable than a ballast tank controlled vessel. A movable hydrofoil could theoretically be adapted from moveable aerofoil technology. This study proves the merit of further investigation into this possibility.
