【作者】 倪崇本；

【导师】 缪国平； 朱仁传；

【作者基本信息】 上海交通大学 ， 船舶与海洋结构物设计制造， 2011， 博士

【摘要】 计算流体力学(CFD)在船舶设计中的应用发展迅速,它能够提高船舶设计的效率和能力,是富有价值的研究方向与热门课题,越来越多的学者从不同的角度对此展开进一步研究。船体绕流是一种高度复杂的三维流动现象,船体周围流场中近船体壁面的黏性流动已十分复杂,并且由于自由面的存在、船体自身受外力影响发生的运动,都大大增加了问题的复杂程度。因此在计入各项外界因素的影响下,对船体周围流场内流体流动的进行准确地数值模拟具有非常重要的意义。随着计算机与信息处理技术的发展、湍流模型的突破、非线性波浪数字模拟技术的发展以及动网格技术的运用,基于CFD的船舶阻力性能综合型研究,已经具有初步的可行性。本论文在对国内外学者对于船舶阻力计算预报的研究进行了较为系统的回顾与总结的基础上,基于商业CFD软件并经二次开发建立数值拖曳水池,可以对航行中的船舶周围流场流体流动进行了全面的数值模拟和阻力计算研究。通过数值拖曳水池中渔政船绕流模拟验证了数值水池在船舶模型尺度阻力预报方面的能力,计算结果与实验数据比较表明数值水池中的船体绕流流场模拟计算结果合理的,能够反映船体阻力变化。针对于模型尺度效应引起的层-湍流转换点位置不同和船体表面粗糙程度对阻力实验结果的影响论文进行了有益探讨。船模实验中由于模型与实船尺度不同,导致物理拖曳水池中模型船首需要加装激流丝,CFD模拟计算验证表明不需要另外考虑这一问题,另外CFD也很好地模拟了船体表面粗糙度增加对摩擦阻力的影响。通过对数值拖曳水池中“船模阻力试验”获得的航行船体黏性阻力和兴波阻力等成分分析、与物理试验的相应阻力成分比较以及阻力预报的分析和讨论,笔者将三因次船体阻力预报方法与CFD数值模拟手段进行了有效地结合,提出了基于CFD数值模拟计算的一种快速预报实船阻力的新预报方法。即在模型尺度下船体黏性阻力采用湍流黏性理论模拟计算叠模模型获得,并给出用于阻力预报的换算形状因子1+k,在理想流体理论范畴下直接求解Euler方程以获得船体的兴波阻力,并基于三因次船体阻力预报方法综合成为船体的总阻力。该方法合理地整合和利用了CFD理论和计算手段,综合考虑了自由表面的非线性、水的黏性以及船体复杂的三维曲面,可以捕捉到准确的自由面形状。无论是湍流黏性理论还是理想流体模型计算,其计算模拟时间都比较短,易于在普通PC机上实现。论文通过S60船型与KCS船型的理论计算与预报,以及和实验结果比较研究,表明该方法计算速度快,经济性好,预报精度满足工程需要,具有较强的工程实用性。对于高速航行的船舶,由于船体航行姿态变化明显,以该吃水下设计浮态为基准的阻力计算结果并不能准确预报其实际航行阻力。论文针对高速行驶下船舶的兴波问题,采用动网格技术实现了基于动力学平衡预报船体航行时姿态变化和阻力计算。在迭代过程中,CFD求解器通过实时计算每一时刻船体所受外力,对船体的下坐与纵倾运动进行更新,最终达到平衡状态。为了改善整个计算过程的稳定性与收敛性,本论文在船体运动响应计算中采用松弛法,对船体运动进行迭代修正。该方法在数值计算过程中经过验证,具有良好的收敛性与稳定性。实践证明,该方法适用的傅汝德数范围广泛,即使是在高航速时下仍然能够避免网格扭曲与计算发散等问题,证明其具有很好的实际工程价值。该方法充分考虑了船体姿态的影响,对高速船的兴波阻力计算预报更为准确。作为一种几年来备受关注的新船型,多体船的水动力性能独具特色,某些研究方法不能直接扩展至多体船的水动力性能研究。本论文利用动网格技术对某多体船进行数值模拟,通过对考虑船体姿态变化的自由模型与不考虑姿态变化的约束模型的压力、波形等方面的对比,探讨了多体船船体姿态对船体水动力性能的影响。在基于CFD动网格技术上建立的动态数值拖曳水池对多体船阻力的计算结果与实验结果比较表明,二者吻合良好,并且该方法计算耗时较少,可以为船体设计提供可靠的依据。更多还原

【Abstract】 Computational Fluid Dynamics (CFD) is applied widely in ship design for it can improve the capacity and efficiency of ship design. It is a hot research topic and more and more researchers focus on it and are studying on it in various academic, engineering and technology opinions. The viscous flow around ship is a complex 3-D phenomena which includes complex viscous flow near ship wall, free surface, ship body motions and so on. Thus numerical simulation of flow around ship which takes the external influence factors into consideration is a task of great challenge and importance. With the rapid development of computational methods and computer technology, now the comprehensive investigation of ship resistance prediction based on the CFD tools is possible.Recent developing and research progress of the ship resistance calculation is systematically reviewed here. The numerical towing tank applied to simulate the water flow around ship is established based on the secondary development of commercial CFD software. The capacity of resistance prediction for model ship voyaging in the numerical towing tank is verified by a physical test of fishery administration ship, the reasonable calculation results are obtained which agree well with the measured ones in physical model experiment. The different transition of laminar flow turning to turbulent flow due to model various scales and the ship hull roughness influence on resistance are discussed in the present paper. In order to solve the problem that the model and full ship are in different scale, boundary layer trip are set up around the model bow in physical model experiment, it is proved here that it is not necessary to do it while CFD simulation method is hired.A new method to predict full-scale ship resistance based on CFD approach is outlined here. The ship form factor is obtained by double-model theory in turbulent flow model, and the wave resistance is calculated by ideal fluid flow and multi-phase theory. Whatever the theory of turbulent flow or ideal fluid flow is used to simulate flow around ship, lesser calculation time is consumed. The simulation can easily be carried out on Personal Computer and it keeps good accuracy. Theoritical calculation and resistance prediction for Ship S60 and KCS are done as well as the comparison with experiment results. It shows the new method fits for engineering application.Since trim and sinkage are significant while vessels advancing forward with high speed, the predicted vessel resistance based on restrained model theory or experiment may not reflect resistance of vessels during voyage. It is necessary to take hull gesture influence into account for resistance prediction of high speed ship. Here the resistance problem of high speed ship is treated by the viscous flow theory regime, the dynamic mesh technique is adopted to coincide with variation of hull gesture of high speed vessel on voyage. The simulation of the models of S60 ship moving in towing tank with high speed are conducted by using the above theory and technique. The calculation results both of the resistance and hull gesture are in good agreement with the experimental data. It indicates the resistance prediction for high speed vessels should take hull gesture into consideration and the dynamic mesh method proposed here is useful to investigate the resistance calculation for high speed vessels.The trimaran ship is a new type ship with unique hydrodynamic characteristic. Some research methods of hydrodynamics for single-hull ship can not be applied to the trimaran ship. Here a numerical towing test of trimaran model is conducted with the aids of dynamic mesh techniques. The rapidity and influence of hull gesture is investigated and resistance of trimaran is forecasted. Compared with experimental data, it is proved that the comprehensive method of resistance prediction promoted here is reliable, and it will be a useful tool at the ship design stage.更多还原