Influence of scale effect on flow field offset for ships in confined waters

IF 3.9 4区 工程技术 Q1 ENGINEERING, MARINE Brodogradnja Pub Date : 2024-01-01 DOI:10.21278/brod75106
ZhongXin Ma
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Abstract

To investigate the flow field characteristics of full-scale ships advancing through confined waters, the international standard container ship (KRISO Container Ship) was considered as a research object in this study. Using the RANS equation, the volume of fluid method and the body force method were selected to investigate the hydrodynamic characteristics of a model-scale ship (the model-scale ratio λ=31.6) and a full-scale ship advancing through confined waters at low speed. A virtual disk was used in the full-scale model to determine the influence of the propeller on the ship’s flow field. First, the feasibility of the numerical calculations was verified. This proves the feasibility of the numerical and grid division methods. The self-propulsion point of the full-scale ship at Fr=0.108 is determined. The calculation cases of model-scale and full-scale ships (with or without virtual disks) at different water depths and distances between the ship and the shore were calculated, and the changes in the hull surface pressure, the flow field around the ship, and the wake fraction near the ship propeller disk in different calculation cases were determined and compared. The variations in the surge force, sway force, and yaw moment between the model- scale and full-scale ships were generally consistent. In very shallow water (H/T=1.3), the non-dimensional force and moment coefficients for model-scale ships increase more rapidly with decreasing distance from shore, suggesting that using model-scale ships to investigate the wall effect in very shallow water will result in predictions that are biased towards safety. By comparing full-scale ships with and without propellers, it was discovered that the surge force, sway force, and yaw moment were marginally greater in the propeller-equipped ship due to the suction effect, and the accompanying flow before and after the propeller was slightly smaller, with less asymmetry.
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尺度效应对封闭水域船舶流场偏移的影响
为研究全尺度船舶在封闭水域中前进时的流场特性,本研究以国际标准集装箱船(KRISO 集装箱船)为研究对象。利用 RANS 方程,选择流体体积法和体力法来研究模型比例船舶(模型比例比 λ=31.6)和低速通过封闭水域的全尺寸船舶的流体动力学特性。在全尺寸模型中使用了一个虚拟圆盘,以确定螺旋桨对船舶流场的影响。首先,验证了数值计算的可行性。这证明了数值计算和网格划分方法的可行性。确定了 Fr=0.108 时全尺寸船舶的自推进点。计算了不同水深和船岸距离下模型船和全尺寸船(有无虚拟盘)的计算情况,确定并比较了不同计算情况下船体表面压力、船周围流场和船螺旋桨盘附近尾流分量的变化。模型船和全尺寸船的涌浪力、摇摆力和偏航力矩的变化基本一致。在极浅水区(H/T=1.3),模型船的非尺寸力和力矩系数随着离岸距离的减小而增加得更快,这表明在极浅水区使用模型船研究船壁效应会导致预测结果偏向安全。通过对比有螺旋桨和无螺旋桨的全尺寸船舶发现,由于吸力效应,有螺旋桨的船舶的涌浪力、摇摆力和偏航力矩略大,螺旋桨前后的伴流略小,不对称性较小。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Brodogradnja
Brodogradnja ENGINEERING, MARINE-
CiteScore
4.30
自引率
38.90%
发文量
33
审稿时长
>12 weeks
期刊介绍: The journal is devoted to multidisciplinary researches in the fields of theoretical and experimental naval architecture and oceanology as well as to challenging problems in shipbuilding as well shipping, offshore and related shipbuilding industries worldwide. The aim of the journal is to integrate technical interests in shipbuilding, ocean engineering, sea and ocean shipping, inland navigation and intermodal transportation as well as environmental issues, overall safety, objects for wind, marine and hydrokinetic renewable energy production and sustainable transportation development at seas, oceans and inland waterways in relations to shipbuilding and naval architecture. The journal focuses on hydrodynamics, structures, reliability, materials, construction, design, optimization, production engineering, building and organization of building, project management, repair and maintenance planning, information systems in shipyards, quality assurance as well as outfitting, powering, autonomous marine vehicles, power plants and equipment onboard. Brodogradnja publishes original scientific papers, review papers, preliminary communications and important professional papers relevant in engineering and technology.
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