水下爆炸作用下船底液舱动态响应的仿真分析

针对水下爆炸作用下舰船底部液舱的动态响应,采用数值方法进行研究。借助有限元程序ABAQUS对1个简单液舱板架结构模型的动态响应进行数值仿真分析,比较了空舱、满载液舱、半载液舱和单层底这4种情况,分析了各层板中点处的压强、应力及加速度等动态参数。结果表明,半载液舱的防护效果最好,能同时缓解水下爆炸对外底板和内底板的冲击作用。     

采用局部的微分求积法求解激波管问题

The localized differential quadrature (LDQ) method is a numerical technique with high accuracy for solving most kinds of nonlinear problems in engineering and can overcome the difficulties of other methods (such as difference method) to numerically evaluate the derivatives of the functions.Its high efficiency and accuracy attract many engineers to apply the method to solve most of the numerical problems in engineering.However,difficulties can still be found in some particular problems.In the following study,the LDQ was applied to solve the Sod shock tube problem.This problem is a very particular kind of problem,which challenges many common numerical methods.Three different examples were given for testing the robustness and accuracy of the LDQ.In the first example,in which common initial conditions and solving methods were given,the numerical oscillations could be found dramatically;in the second example,the initial conditions were adjusted appropriately and the numerical oscillations were less dramatic than that in the first example;in the third example,the momentum equation of the Sod shock tube problem was corrected by adding artificial viscosity,causing the numerical oscillations to nearly disappear in the process of calculation.The numerical results presented demonstrate the detailed difficulties encountered in the calculations,which need to be improved in future work.However,in summary,the localized differential quadrature is shown to be a trustworthy method for solving most of the nonlinear problems in engineering.     

铝合金舰艇在水下冲击波作用下动态响应的数值研究

使用ABAQUS中内嵌的声 - 固耦合法计算了圆板模型遭受水下冲击波载荷作用的响应,并将计算结果与实验值进行比较,数值结果与实验值吻合良好,验证了声 - 固耦合法模拟水下爆炸的准确性;对铝合金圆板和钢板进行了比较,考虑了结构质量,材料应变率和屈服极限,药量和爆距的影响;建立了1艘小型铝合金艇的有限元模型,使用同样的方法分析了铝合金艇遭受水下冲击波载荷的动力响应特性.得出了铝合金艇典型位置的加速度、速度和位移等响应量的时间历程曲线.此外,还得出了塑性变形区域和塑性变形曲线.这些计算结果对铝合金舰艇的抗冲击特性具有一定参考价值.     

“发展之路”号自航半潜船船体改装设计研究

半潜船是专门运输无法分割的大型整体设备的高技术含量、高附加值船舶,在世界上为数不多。特别是改装半潜船,受到的限制较多,加之船型特殊,国内外可供参考资料缺乏。＂发展之路＂号是世界首艘由液化石油气船改装而成的自航半潜船。概述了该船的主要技术性能和特点,从总布置、结构强度、稳性等方面介绍了该船在改装设计中的难点和要点,为此类船舶的改装设计提供了新的思路。     

分析水中结构自由振动的三维附加质量矩阵法

船舶总体振动分析需考虑对船体外部水的影响。通过建立水域三维有限元模型进行计算或者先计算出附加质量后,加入到结构质量中进行计算。随着有限元技术的发展,船舶大都采用三维有限元建模。传统方法,例如刘易斯附加水质量法,虽然考虑到纵向变形,但确没有忽略船体横剖面的变形,因而不够准确。采用三维边界元方法,考虑水中结构振动的三维效应,计算三维附加质量矩阵,并对水中结构振动进行分析。结果表明,水中结构振动是三维变形,应该采用三维附加质量矩阵进行振动分析。     

二维边界层流动转捩过程的数值计算(英文)

As a basic problem in many engineering applications, transition from laminar to turbulence still remains a difficult problem in computational fluid dynamics(CFD). A numerical study of one transitional flow in two-dimensional is conducted by Reynolds averaged numerical simulation(RANS) in this paper. Turbulence model plays a significant role in the complex flows' simulation, and four advanced turbulence models are evaluated. Numerical solution of frictional resistance coefficient is compared with the measured one in the transitional zone, which indicates that Wilcox(2006) k-ω model with correction is the best candidate. Comparisons of numerical and analytical solutions for dimensionless velocity show that averaged streamwise dimensionless velocity profiles correct the shape rapidly in transitional region. Furthermore, turbulence quantities such as turbulence kinetic energy, eddy viscosity, and Reynolds stress are also studied, which are helpful to learn the transition's behavior.     

结构物出水过程中的自由液面变形研究

利用有限体积法( FVM)研究了圆柱形物体垂直出水的问题.物体以恒定速度垂直出水时,初始自由液面会受到物体的抬升作用而发生变形.自由液面的峰值变化与物体的初始深度有关,但当初始深度Y＞5R时其对液面变形的影响不变.研究还发现液面变形的峰值与物体的长度无关,与物体的头、尾部形状及宽度关系较大.头部平整的物体出水时的液面峰值很大,而头部尖锐的物体出水时液面峰值较小,在双30°锥角形下,液面可以看到明显的波纹.     

三体船随浪中的破舱稳性研究

以一三体船型为例,研究了三体船型在波浪中的破舱稳性。对不同的破舱位置和侧体位置的多种方案进行了计算,结果表明:侧体位置不同时,最危险的破舱位置亦不同,并且破舱位置对稳性损失的影响随着侧体横向位置的增大而减小;侧体位置位于船舯时破舱稳性较好,侧体横向距离越大破舱稳性越好。     

深海立管涡激损伤的虚拟激励法计算

针对深海立管长细比非常大的结构特性,使用索模型单元计算结构的非线性刚度阵,并验证了模型的有效性;在立管离散点处的平面上考虑结构与流体的耦合作用,采用离散涡方法计算了立管二维模型在均匀海流下的涡激升力载荷,为随机振动分析提供载荷谱,用于构造虚拟激励。最终将立管的涡激振动看作平稳随机过程,采用随机振动理论中的虚拟激励法求解立管在涡激力激励下的响应。基于P-M准则,对响应进行计算得到立管的年损伤率,实现了深海立管的疲劳损伤预报。     

两自由度运动圆柱绕流的离散涡方法模拟

应用离散涡数值方法(Discrete Vortex Method,DVM)对弹性支承的二维圆柱绕流的涡激振动(VIV)问题进行数值模拟,研究单自由度横向运动系统、两自由度系统横向和流向耦合运动这两种模型的计算结果,得到了不同质量比、不同折合速度下的尾涡形状、受力系数和圆柱响应曲线,并分别提取了单自由度和两自由度两种模型所得到的横向振幅进行对比.总结出受质量比和自由度数影响的圆柱响应的变化规律,证实了锁定lock-in现象的发生过程.通过与实验结果的对比,验证了计算结果较为合理和可靠,说明离散涡方法是研究涡激振动问题的有效手段,并且它能够适应高雷诺数下的计算,并且认为圆柱的流向运动对涡激振动起着促进作用,在数值模拟中是应当予以重视的.计算过程采用FORTRAN语言编程实现.