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.     

不同海况下小侧体三体船的艏部结构砰击特性

本文运用CFD软件STAR-CCM+建立三体船在波浪条件下的三维砰击模型,采用重叠网格技术结合船舶六自由度系统模拟船体的砰击运动,对不同波高、波长以及不同航速下的船体砰击进行数值模拟,对比分析各工况下船体结构的运动响应和砰击特征。数值模拟结果表明：航速变化对船体砰击压力有显著影响,而波高和波长的变化对砰击压力影响较小但也不可忽视。     

深水铺管船技术研究

海底管道在海洋石油天然气的运输方面起到越来越重要的作用,但随着铺管海域水深的增加,对海底管道的铺设方法和主要铺设工具——铺管船也提出了更高的要求.文章介绍了目前普遍使用的几种深水铺管船的船型特点及铺管方法,并以ABS规范为基准,详细说明了深水铺管船入级在总体、结构、舾装等方面应达到的各项要求.     

长江上海段圆圆沙警戒区航行规则的思考

通过对长江上海段圆圆沙警戒区通航现状和船舶流向的分析，结合定线制规则、海员通常航行习惯和船舶操纵等相关知识，给航经此水域船舶的安全航行和船舶间的避碰提出一些可行性的建议，这些建议对保障船舶在该水域安全航行具有重要意义。     

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.     

基于共同结构规范的46000t灵便型成品油船设计

针对灵便型成品油船，基于共同结构规范进行了较详细的全船结构设计分析，并探讨了共同结构规范的特点及其对该型船设计的影响。     

Numerical study on the dynamic response of a truncated ship-hull structure under asymmetrical slamming

Dynamic response of ship-hull structure under slamming has tracked widespread attention in the marine structural design. However, our understanding on the dynamic characteristics largely relies on the symmetrical slamming cases. This paper presented a preliminary numerical investigation on the dynamic response of a truncated ship-hull structure under asymmetrical slamming based on the uncoupled CFD-FE method. Asymmetrical slamming loads were predicted through combining the seakeeping analysis and CFD method. In there, three kinds of motions (vertical, horizontal and roll motions) of 2D ship sections were obtained through the seakeeping analysis and then the slamming pressure was predicted through simulating the water entry with various motions based on CFD method. The dynamic response was analyzed through finite element method. Numerical predictions including ship motions, slamming loads and dynamic analysis were validated against published experimental data and numerical calculations. The characteristics of asymmetrical slamming loads were analyzed showing obvious asymmetry in space, and the dynamic characteristic of the ship bow structure was further clarified through discussing the deformation and stress distribution. These results are useful for readers for better understanding the dynamic characteristics of the bow structure under slamming.     

Equivalent design pressure for ship plates subjected to moving slamming impact loads

When a ship navigates at sea, the slamming impact can generate significant load pulses which move up along the hull plating. The effect of the moving pressure has so far not been explicitly considered in the Rules and Regulations for the Classification of Ships. Based on a modal superposition method and the Lagrange equation, this paper derives analytical solutions to study the elastic dynamic responses of fully clamped rectangular plates under moving pressure impact loads. The spatial variation of the moving slamming impact pressure is simplified to three types of impact loads, i.e. a rectangular pulse, a linearly decaying pulse and an exponentially decaying pulse. The dynamic responses of fully clamped rectangular plates under the moving slamming impact pressure are calculated in order to investigate the influence of the load pulse shapes and moving speed on the plate structural behaviour. It is found that the structural response of the plate increases with the increase of the moving speed. The response of the plate subjected to a moving pressure impact load is smaller than the case when the plate is subjected to a spatially uniform distributed impact load with the same load amplitude and load duration. In order to quantify the effect of the moving speed on the dynamic load, a Dynamic Moving Load Coefficient (DMLC) is introduced as the ratio between the dynamic load factor for the moving impact load and that under the spatially uniform distributed impact load. An expression for DMLC is proposed based on analyses of various scenarios using the developed analytical model. Finally an empirical formula which transforms the moving impact loads to an equivalent static load is proposed.     

船舶砰击强度计算方法研究

船舶在航行时发生砰击是一种高度非线性的物理现象。本文基于势流理论Rankine源法,研究用时域非线性方法计算船舶运动响应,获得船波垂向相对运动速度;并选取合适的砰击压力系数,计算船舶砰击载荷。最后用该方法评估了一艘集装箱船艏部砰击强度,验证了该方法的合理性。     

基于新旧共同规范的主要支撑构件曲形面板结构强度对比分析

为明确共同规范对主要支撑构件曲形面板有效面积计算公式更新后主要支撑构件曲形面板有效系数的变化,通过实例分析规范修改对主要支撑构件曲形面板有效性的影响,认为规范修改对于非对称曲形面板的影响远大于对称曲形面板,可通过设置径向肘板、将非对称曲形面板改为对称曲形面板、改变面板尺度比,使得有效系数最大,可采用细网格进一步分析,进...