Numerical and experimental analysis of bow flare slamming on a Ro–Ro vessel in regular oblique waves

A method for the prediction of slamming loads on ship hulls is presented and validated for a 20-knot, 120-m car carrier. A nonlinear strip theory is used to calculate the relative motions of ship and wave. The relative vertical and roll velocities for a slamming event are given as input to the slamming calculation program, which is based on a generalized two-dimensional Wagner formulation and solved by the boundary element method. The method is fast and robust. Model tests of a car carrier have been carried out in regular head, bow, and bow quartering waves of various heights. Slamming on two panels in the upper part of the bow flare has been studied. It has been found that the water pile-up around the bow due to the forward speed of the vessel significantly increases the slamming pressures. A simplified way of including this effect is presented. When the calculated slamming pressures are corrected for 3D effects, they compare well with the measured data. Since the effect of the wave elevation due to the forward speed and the effect of three-dimensional flow act in opposite directions, excluding both of them produced results that also agreed quite well with the experiments, especially for the most severe slamming events.     

土体中应力分布基本规律的探讨

基于土体的颗粒结构和只有颗粒接触传递应力的特性，对不同姿态颗粒接触中应力传递的机理分析，揭示了土体在相对静态下存在主动力的应力扩散效应和强被动力的应力集中效应，及其形成的土体中应力分布基本规律。主动力的应力场是以其所在土层的应力扩散角θ向外扩散的园锥形应力范围，在应力场内应力扩散分布，主应力方向不变，且伴有与之垂直的法向应力，应力分布均衡了应力场内颗粒和支承面的位移趋势。强被动力的支承面上存在以θ角向外扩散倒锥台形的应力平衡范围，在此范围内反向应力集中作用到强支承面，强支承面主导了其所在应力场的应力分布。土拱效应是应力集中效应的衍生效应，是相邻的同向强支承反力的应力平衡范围发生重迭时产生的现象。     

Efficient calculation of slamming pressures on ships in irregular seas

An efficient method for calculation of the slamming pressures on ship hulls in irregular waves is presented and validated for a 290-m cruise ship. Nonlinear strip theory was used to calculate the ship–wave relative motions. The relative vertical and roll velocities for a slamming event were input to the slamming calculation program, which used a two-dimensional boundary element method (BEM) based on the generalized 2D Wagner formulation presented by Zhao et al. To improve the calculation efficiency, the method was divided into two separate steps. In the first step, the velocity potentials were calculated for unit relative velocities between the section and the water. In the next step, these precalculated velocity potentials were used together with the real relative velocities experienced in a seaway to calculate the slamming pressure and total slamming force on the section. This saved considerable computer time for slamming calculations in irregular waves, without significant loss of accuracy. The calculated slamming pressures on the bow flare of the cruise ship agreed quite well with the measured values, at least for time windows in which the calculated and experimental ship motions agreed well. A simplified method for calculation of the instantaneous peak pressure on each ship section in irregular waves is also presented. The method was used to identify slamming events to be analyzed with the more refined 2D BEM method, but comparisons with measured values indicate that the method may also be used for a quick quantitative assessment of the maximum slamming pressures.     

海洋平台火炬塔筒体结构应力分析

针对海洋平台火炬塔筒体结构强度设计问题,采用Ansys软件的静力学模块对单个火炬塔筒体和3个火炬塔筒体进行静力分析,得到不同工况条件下的结构应力值和变形位移值。结果表明,单个火炬塔筒体可承受的最大压力载荷大于3个火炬塔筒体可承受的最大压力载荷。火炬塔筒体的分析方法和结果对后续石油化工废气处理装置的设计和安装具有一定的指导意义。     

Radio Fiber Fine Structure During the Solar Flare on July 14，2000

Introduction　　AmongthefinestructuressuperposedonthecontinuumemissionofsolartypeIVradiobursts,oneofthemostfrequentlyobservedisfiber .Fibers,orintermediatedriftbursts ,werefirstobservedinsolartypeIVcontinuabyYoungetalin 196 1[1] .Thefiberstructuresinmetri…     

平湖八角亭平台的优化设计

作为平湖油气田整体开发的二期工程，通过利用已有生产综合平台的设施能力分析，研究了八角亭平台设计中的一些设备（包括火炬分液罐、阅排罐、海管等），优化了八角亭平台设计，降低了投资成本。     

大型集装箱船迎浪航行的外飘砰击压力研究

该文采用直接计算法研究一艘大型集装箱船迎浪航行时的外飘砰击压力特点。先基于三维势流理论Rankine面元法,应用DNV船级社的商业软件Wasim计算出该船在压载时不同海况下以不同航速航行时在非规则波中时域内的非线性运动响应时历,再根据Wagner型冲击理论计算得到该集装箱船艏外飘区域的外飘砰击压力。最后,依据概率随机理论,得到不同工况下的外飘砰击概率以及外飘砰击压力极值,并分析概率和极值特点。     

大型集装箱船加装混合式脱硫系统船体设计

基于多型超大型集装箱船加装镁基法混合式脱硫系统工程项目,从船体设计的角度分析总结了改装要点。根据混合式脱硫塔系统新增的设备和舱柜,以及布置和系统上的要求,重点研究了加装过程中烟囱外形和结构尺寸、舱柜布置、烟囱振动以及防沉淀等关键技术问题。本文为大型箱船或其它船型安装混合式废气脱硫提供了技术参考和设计经验。     

超大型集装箱船艏艉砰击强度直接计算方法

超大型集装箱船的船艏显著外飘、船艉宽平外悬,使其在恶劣海况下航行时容易发生严重的砰击。为确保船体艏艉部结构在砰击中不发生损坏,需要研究作用到艏艉外板上的砰击压力,并以此为设计载荷来校核外板和相连结构的强度。目前对集装箱船砰击局部强度的校核要求仍以经验公式为主,但是为提高对超大尺度船舶强度校核的可靠性,近年来推出了砰击的直接分析方法。本文初步分析了砰击直接分析方法的基本原理,并运用该方法对20,000 TEU集装箱船的艏、艉部砰击压力以及最小板厚要求进行了研讨,其结果可为超大型集装箱船的结构设计提供重要的参考。     

基于全船建模的航速对船首外飘砰击影响研究

建立二维楔形体入水模型,验证入水砰击仿真方法可靠性,对集装箱船体进行全船体建模,导入船体运动参数,增加船体的纵摇运动,采用一般耦合算法(General coupling),流体域用Euler单元模拟,船体设为刚体,划分为Lagrange有限元网格,对船体进行入水仿真.对比不同工况下的结果表明:全船模拟时船型纵向斜升角会发生变化,导致航速对船首入水砰击压力的影响较大,随着航速的增加,入水砰击压力变大,同时航速还会使砰击压力峰值位置发生变化.