【作者】 冯大奎；

【导师】 叶恒奎；

【作者基本信息】 华中科技大学 ， 船舶与海洋结构物设计与制造， 2008， 博士

【摘要】 如何利用数值计算方法来准确预报船舶兴波阻力与兴波波形,并为船舶设计服务,一直都是船舶阻力理论研究中的重要内容与难点之一,同时也是船型优化等工程问题的关键。本文首先回顾了绕船舶自由面流动的势流和粘性流理论,介绍了自由面兴波模拟的数值方法。回顾了定常间接边界元兴波计算的两种方法:基于Havelock源的格林函数法,非奇异的Rankine源方法,在所有边界面上布置Rankine源。以Wigley船为例,提供了非奇异Rankine源方法的兴波波形和兴波阻力系数。利用了时域线性直接边界元法计算船舶兴波。边界积分方程由格林第二定理获得,奇点的速度势由边界上未知强度的源和偶极积分表示,影响系数通过解析的方法求解,物面上的法向速度由物面边界条件决定,自由面上的速度势由线性时域自由面边界条件更新。辐射条件不需要特别给定。自由面计算域边界不随时间变化。提出了船体割划水面的动网格技术。本文以Wigley船为例,讨论了自由面、船体表面网格划分和时间步长对计算结果的影响,并给出了稳定时刻自由面波形和线性兴波阻力计算结果。采用开式尾—静力修正和虚长度的方法分别计算方尾船舶兴波波形和兴波阻力,计算结果与试验结果一致。发展了强非线性时域直接边界元方法,提出了满足自由面移动计算域辐射条件的方法。每个时步自由面上的速度势和节点漂移量通过全非线性Lagrange型自由面边界条件求解,重新进行网格划分得到下一个时步的自由面形状。本文以Wigley单体船为例,比较了自由面固定计算域和移动计算域兴波波形。给出了近水面潜体和双体船的非线性兴波计算结果,并讨论了双体船片体间距变化对兴波阻力的影响。建立了考虑双体船片体两侧非对称流动的兴波计算方法,片体作为升力体考虑,尾涡面上施加压力Kutta条件。文中给出了考虑片体两侧流动不对称性Wigley双体船的计算结果,并与不考虑尾涡效应双体船兴波计算结果进行了比较。这种方法可以用来求解近水面水翼绕流水动力性能。尝试采用有限体积法离散求解标准k—ε湍流方程,运用VOF的方法模拟绕船体自由面粘性流动。并以Wigley船为例,给出了船体表面的压力分布和兴波波形及阻力结果,并与试验结果比较证明了粘性绕流计算的可靠性。更多还原

【Abstract】 Using numerical method to predict the ship resistance and wave pattern generated by ship motion is one of important work for scientists whose research interest is ship hydrodynamics. It is also a very important tool for the ship design and ship hull optimization. The objective of this thesis is to develop the numerical scheme to simulate the free surface flow around the ship hull.First the developments of using potential method and viscous fluid flow simulate the free surface flow around the ship hull were reviewed carefully. The numerical method of simulation the free surface flow was presented.Two undirected boundary element methods under steady state were presented in second chapter: Green function method based on Havelock Source and Non-singular Ranking Source method. The Green function method based on Havelock Source set the Havelock Source on the hull surface and the boundary condition of free surface satisfy the linear condition. Non-singular Ranking Source method fixed the Ranking Source on the hull surface and raised panels above the free surface combined with collocation-points to avoid high order singularity with shifting up-stream to satisfy the radiation condition. The Wigley hull was selected to validate these two methods and the wave pattern and wave resistance were presented in this chapter.The linear direct boundary element method in time domain was used to simulate the wave generated by ship hull motion. Wigley hull was used to study the influence of the free surface, grid structure along the hull surface and time domain on the simulation results. The simulation results of free surface wave pattern and linear wave resistance were also presented. The open stern-static pressure mended and virtual appendage were used to computed wave pattern and wave resistance of ship hull, the simulation results matched with the experimental results.The strong non-linear directed boundary element method was presented which was used to simulate the flow around Wigley hull. To save the computation time, the dimension of simulation domain was set which increase the dimension of simulation domain had no effect on the simulation results. The grid regeneration technology was adopted during simulation procedure while the ship hull moving forward inside the simulation domain. The Wigley hull was used to test the numerical scheme developed in this thesis. The comparison of wave pattern between fixing and moving simulation domain was made and the non-linear wave generation simulation results for submerge body near the free surface and catamaran were presented.The influence on the wave making resistance of the distance between the twin hulls for catamaran was discussed also. Chapter five studied the influence of asymmetry flow of twin hulls. The hull body was considered as the lifted body because of the difference of the flow between the hulls. The simulation results of wave pattern for catamaran using Wigley hull as the submerge body with the consideration of the asymmetry effects of the hulls were presented. This simulation result was compared with the simulation result which trailing vortex was not considered.Finally the viscous flow around the Wigley hull with free surface was studied. The numerical technologies include finite volume method and volume of free surface method. The standard k-εturbulent model was employed in viscous simulation. The simulation results of wave profile along ship hull and wave contour on free surface were presented. The simulation results matched well with the results using potential method and available experimental data.更多还原