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141.
文章将船舶进水时域过程作为拟静态处理,计算出每个时刻的内外液体交换量,然后使用损失浮力法求解浮态方程计算该时刻的船舶浮态,直到进水过程终止.提出了一种适用于破口内外液体密度不同且互不相溶时计算液体交换的方法,给出了不同粘度液体的流量系数回归方程,并且针对一艘液货船破损后内外液体的交换情况进行了计算.提出的方法可以为破损船舶的救援以及防污染工作提供很大帮助. 相似文献
142.
通过充分利用DNV的Sesam软件和MSC.patran以及MSC.Nastran几个软件的优势,对一艘88m超规范甲板驳船进行了横向强度分析,找出船舶在不同工况下所对应的承载规律。并在频域内采用三维线性势流理论的波浪载荷计算方法对甲板驳船进行了波浪载荷直接计算,分析了不同工况先载荷分布的特点,并将计算结果与CCS规范和DNV规范中的结果进行了比较,为合理选取波浪载荷提供依据。 相似文献
143.
This paper is concerned with the hydroelastic problem of a pontoon-type, very large floating structure (VLFS) edged with the perforated plates, non-perforated plates or their combination anti-motion device both numerically and experimentally. A direct time domain modal expansion method, taking amount of the time domain Kelvin sources in hydrodynamic forces, in which the fluid flows across the perforated anti-motion plate by applying the Darcy's law, is applied to the fluid–structure interaction problem. A quarter of numerical model is built based on the symmetry of flow field and structure in hydrodynamic forces, and special care is paid to the rapid and accurate evaluation of time domain free-surface Green functions and its spatial derivatives in finite water depth by using interpolation–tabulation method. Using the developed numerical tools and the model tests conducted in a wave basin, the response-reduction efficiency of the perforated plates is systematically assessed for various wave and anti-motion plate parameters, such as plate width, porosity and submergence depth. As a result of the parametric study, the porosity 0.11 is selected as the optimal porosity, and the relationship between the porosity and the porous parameter is developed by using the least-squares fitting scheme. After simulation and verification, the dual anti-motion plates which are the perforated-impermeable-plate combination attached to the fore-end and back-end of the VLFS, are designed for more wave energy dissipation and added damping. Considering variation of the water depths in offshore, discussion on the effectiveness of these anti-motion devices at different water depths is highlighted. 相似文献
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在梳理流噪声数值预报方法的基础上,采用流场大涡模拟(large eddy simulation,LES)和声学边界元(boundary element method,BEM)方法在频域内计算预报了船体流噪声谱曲线,求取了其等效声中心.LES计算时选用动力学Smagorinsky-Lilly(dynamic Smagorinsky-Lilly,DSM)亚格子应力模型,流噪声由船体壁面脉动压力和法向速度特性决定,声源节点和声节点变量传递采用一对一的守恒传递方式.结果表明:某型船在航速14 kn时,裸船体流噪声在20 Hz~2 kHz频段内总声源级为133dB;当计算有效频段扩展到20 kHz时,总声源级达143.3 dB.流噪声主要来源于兴波引起的涡量,且主要集中于100 Hz~10 kHz频段.球首尾流区和船体尾涡区对流噪声辐射量贡献明显,特别是球首尾流区,对全频段都有明显的贡献,为水面舰艇流噪声研究提供了一条新的途径. 相似文献
148.
Riser long-term fatigue performance is an important design consideration. Although extensive application of irregular sea analysis in time domain with the rainflow counting technique for post-processing is regarded as the most accurate of the approaches for fatigue analysis, it does suffer from some limitations, such as the computational effort. For this reason, two computationally efficient approaches are employed to perform the fatigue analysis of a deepwater top-tensioned riser, based on the Longuet-Higgins distribution and time domain scaling respectively. With Longuet-Higgins distribution irregular wave sea states are expanded into their individual wave bins. These regular wave simulations are of short duration and consequently run quickly. Using the time domain scaling technique, the number of irregular wave runs can be performed for a comparatively small number of load cases and hence reduces the calculation time. The results showed a reasonable accuracy and significant efficiency for both approaches, compared with those from the equivalent rainflow analysis. With much less computational effort and disk storage requirement, the approaches outlined in this paper can therefore be used for the fatigue assessment of deepwater risers in industry practice. 相似文献
149.
基于切片法建立物体在静水中浮体上纵向运动时浮体的水动力特征及运动微分方程。物体对浮体的垂向作用力考虑为瞬时压力,采用4阶龙格库塔法求解浮体运动微分方程,并将计算值与试验数据进行比较。 相似文献
150.