【作者】 王化明；

【导师】 邹早建；

【作者基本信息】 上海交通大学 ， 船舶与海洋结构物设计制造， 2009， 博士

【摘要】 船舶操纵性是船舶重要的水动力性能之一,和船舶的航行安全性密切相关。近二十年来,随着现代船舶向高速化、大型化、专业化方向发展,船舶操纵变得更加困难,发生海难事故造成的后果更为严重;特别是由于船舶的大型化,以前显得宽阔的水域,如近岸、入海口、港湾和内河航道等船舶航行的水域,随着船舶吃水、船宽尺度的增加,水深相对变浅,宽度相对变窄,成为所谓的限制水域。相对于无限水域的航行环境,一方面,船舶面临着更多的障碍物,致使发生碰撞、触礁、搁浅的可能性大大增加,从而对船舶操纵性有着更高的要求;另一方面,由于浅底、岸壁及其它障碍物的存在而使船舶受到的水动力和力矩更加复杂,从而使船舶操纵变得更加困难。正因为如此,限制水域中船舶操纵性研究已变得非常迫切,成为当前船舶水动力学领域的前沿热点课题。最近十多年来,随着计算机科学技术的飞速发展,计算机的容量和速度得到了极大提高,为船舶计算流体动力学(Computational Fluid Dynamics, CFD)技术的发展和实用化提供了必要的硬件条件,也使得计算复杂的船舶操纵运动流场和水动力成为可能。本文基于CFD通用软件FLUENT平台并利用其UDF(用户自定义函数)功能进行二次开发,通过求解雷诺平均N-S方程(简称RANS方程)对限制水域中船舶操纵运动粘性绕流场进行数值模拟,并计算作用于船体上的操纵水动力。在采用RANS方法计算操纵运动船舶水动力的过程中,合适的湍流模型和高质量的计算网格是成功进行数值模拟的关键。本文对目前在船舶粘性水动力计算中应用最广泛的5种两方程湍流模型进行比较研究,通过其计算结果与试验值的比较验证,确定了适合于限制水域中操纵运动船舶粘性绕流数值模拟的湍流模型。同时,对计算区域分别采用结构化网格、非结构化网格和带近壁面层的混合网格进行网格划分,并以这3类网格进行船舶操纵水动力的计算,通过与试验值的比较,分析了不同网格类型在船舶操纵运动粘性流求解中的模拟精度。综合考虑目前的计算效率与网格生成耗费的时间,本文通过数值实验,确认在限制水域实际船型操纵运动粘性流计算中,带近壁面层的混合网格是一种实用性和可靠性俱优的网格类型。对于不同几何形状的实际船型,本文给出了一些便捷有效的高质量近壁面层混合网格划分的建议。本文针对如下几种典型的限制水域中的船舶操纵运动,通过求解RANS方程,对其粘性流场和水动力进行了数值研究:(1)浅水域船舶斜航运动的粘性绕流场及水动力数值计算研究。以KVLCC2大型油轮为研究对象,首先对船舶深水斜航运动粘性流计算中计算区域的确定、网格依赖性的检验以及湍流模型的选取等问题进行研究,通过将本文数值计算结果与他人的试验结果和在上海交通大学拖曳水池进行的船模斜拖试验结果相比较,验证了本文数值方法的有效性。在此基础上,采用本文的数值方法对不同水深情况下船舶以不同漂角斜航时所受的阻力、横向力和转首力矩进行预报,并分析了水深和漂角对斜航运动船舶水动力的影响。(2)浅水域船舶回转运动的粘性绕流场及水动力数值计算研究。以大阪号油轮(Esso Osaka tanker)为研究对象,通过求解旋转坐标系中的控制方程,对船舶在不同水深情况下的回转运动绕流场进行数值模拟。首先对深水情况下船模的定常回转进行了计算,并与试验值进行比较,验证了本文数值方法的有效性;然后对船模在7种不同的水深情况下的粘性流场和水动力进行计算,得到了水深对回转运动船舶所受的粘性水动力及力矩的影响。(3)近岸航行船舶的粘性绕流场及水动力数值计算研究。以系列60(Cb=0.6)船型为研究对象,首先对系列60这一类船体首尾部尖廋、中间底部平坦的船型的计算域网格划分进行了探讨,提出了一种有效的高质量近壁面层网格生成方法;然后对系列60船模在不同的水深情况下以不同的离岸距离近岸航行时的粘性流场和水动力进行了计算研究。通过对计算结果的分析,得出了近岸航行船舶所受的水动力随岸壁距离和水深的变化规律。(4)浅水域船舶非定常横向停靠运动粘性绕流场及水动力数值计算研究。通过求解非定常RANS方程,对船舶非定常横向停靠运动的瞬时流场进行数值模拟,并预报在停靠过程中作用于船体上的粘性水动力随时间的变化情况。首先,以标准Wigley数学船型为例,对船舶非定常横向停靠运动瞬态问题数值模拟的关键技术,包括时间步长、压力-速度耦合算法以及适用于船舶横向运动的湍流模型进行了研究,并将标准Wigley模型在不同水深情况下作非定常横向停靠运动所受的横向水动力计算结果与试验值进行了比较,验证了本文数值方法的有效性。然后,以KVLCC2大型油轮为例,对实际船舶的非定常横向停靠运动的粘性绕流场进行了数值模拟,并对作用于船体上的纵向和横向水动力以及转首力矩的时历变化情况进行了预报。本文采用基于RANS方程求解的粘性流数值方法对多种限制水域中的船舶操纵运动粘性绕流场进行了数值模拟,捕捉到了操纵运动船舶周围的流场特征,通过观察和分析这些流场信息,人们可以深入理解操纵运动船舶在限制水域中所受水动力的变化机理。本文数值方法能较准确地预报作用于限制水域操纵运动船体上的粘性水动力,揭示操纵运动水动力随水深、岸壁距离等因素的变化规律以及船舶非定常操纵运动水动力的时历变化情况,这对于研究限制水域中的船舶操纵与控制问题具有重要的理论意义和实用价值。更多还原

【Abstract】 Manoeuvrability is one of the most important hydrodynamic performances of ships, which has a close relationship with navigation safety. In the last two decades, with the development of modern ships towards higher speed, large-sized and specialized ones, ship manoeuvring is becoming more and more difficult, and the results of marine accident would be more serious once it happens. Especially with the ship size becoming lager, waters such as the water area near bank, the estuary region, the gulf and the inland channel are becoming shallower and narrower relatively, which are the so-called restricted waters. Compared with the case of unrestricted waters, ships navigating in restricted waters face more obstacles, which increases the possibility of collision and grounding accidents. This requires ships to possess better manoeuvring performance. On the other hand, the shallow bottom, the bank and other obstacles make the hydrodynamic forces and moments acting on the hull more complicated, which makes the ship manoeuvring more difficult. Therefore, it is urgent to study the ship manoeuvrability in restricted waters. At present, this research is becoming one of the hot topics in the field of ship hydrodynamics.During the last decade, with the rapid development of computer science and technology, the performance of computer has been improved greatly. This has provided the necessary hardware condition for the development and practical application of Computational Fluid Dynamics (CFD) in ship hydrodynamics, and made it possible to simulate the complicated flow around a manoeuvring ship and to calculate the hydrodynamic forces on the ship. In this thesis, a general purpose CFD code, FLUENT, and its UDF (User Defined Functions) are used for simulating the viscous flows around a manoeuvring ship in restricted waters and calculating the hydrodynamic forces acting on the hull by solving the Reynolds-Averaged Navier-Stokes (RANS) equations. In the process of numerical calculation of the hydrodynamic forces, suitable turbulence model and high qualified grid are the keys to a successful simulation. The numerical results of viscous hydrodynamic forces on a ship in restricted waters obtained with five two-equation turbulence models, which are widely used in computation of ship viscous hydrodynamic forces, are compared with measurements to determine the suitable model. Structured grids, unstructured grids and hybrid grids with the layer near the boundary are adopted to divide the computational region, and computation of the hydrodynamic forces is conducted with these three grids. The accuracy of the numerical results with these grids is analyzed by comparing the numerical results with experimental ones. By comprehensively considering both the computational efficiency and the time consumed in the grids generation, it is found by numerical experiments that the hybrid grids with the layer near the boundary is a convenient and effective one. For some real ships with different ship form, suggestions are put forward for a fast and efficient grid generation of high-qualified hybrid grids.For some typical ship manoeuvring motions in restricted waters, numerical study on simulation of the viscous flow and calculation of the hydrodynamic forces is carried out by solving the RANS equations: (1) Numerical study on the viscous flow and the hydrodynamic forces on a ship in oblique motion in shallow water. The numerical study is carried out for a KVLCC2 tanker. Firstly, for the ship in oblique motion in deep water, determination of the computational domain, check of the grid dependence and selection of the turbulence model in numerical simulation are investigated. The effectivity of the numerical method is validated by comparing the numerical results with experimental data published in literature and the experimental results obtained by oblique towing test in the towing tank of Shanghai Jiao Tong University. Then the numerical method is applied to predict the resistance, the lateral force and yaw moment on the ship at different drift angles in shallow water with different water depths, and the influences of the water depth and drift angle on the hydrodynamic forces are analyzed.(2) Numerical study on the viscous flow and the hydrodynamic forces on a ship in turning motion in shallow water. The numerical study is carried out for the Esso Osaka tanker. By solving the control equations in the rotating coordinate system, numerical simulation of the viscous flow is conducted for the ship in turning motion at different water depths. Firstly, for the ship in turning motion in deep water, computations are performed and the numerical results of the hydrodynamic forces are compared with measurements to verify the numerical method. Then the viscous flow and the hydrodynamic forces are calculated for the ship model at seven water depths. The influence of the water depth on the hydrodynamic forces acting on the ship in turning motion is obtained.(3) Numerical study on the viscous flow and the hydrodynamic forces on a ship sailing along a bank. The numerical study is carried out for a Series 60 ship with Cb=0.6. Firstly, grid generation of computational domain is investigated for this ship form with thin bow and stern and a fat middle ship. An efficient grid generation of high-qualified hybrid grids with the layer near the boundary is proposed. Then the numerical study is conducted for the viscous flow and the hydrodynamic forces acting on the ship sailing at different water depths and different distances to the bank. By analyzing the numerical results, the changing tendence of the hydrodynamic forces with the water depth and the distance to the bank is obtained.(4) Numerical study on the viscous flow and the hydrodynamic forces acting on a ship undergoing unsteady lateral berthing motion in shallow water. By solving the unsteady RANS equations, numerical simulation of the transient viscous flow around a ship in unsteady lateral berthing motion is conducted, and the time history of the viscous force on the hull during the berthing process is predicted. Firstly, for a standard Wigley mathematical ship form, key techniques in numerical simulation of the transient viscous flow around a ship in unsteady lateral berthing motion, such as time step, pressure-velocity coupling algorithm and the turbulance model suitable for simulation, are investigated. The numerical results of the lateral forces on the Wigley model in unsteady lateral berthing motion at different water depths are compared with experimental data to verify the numerical method. Then for a real ship form, KVLCC2 tanker, numerical simulation of the viscous flow around the ship in unsteady lateral berthing motion is conducted, and the time histories of the hydrodynamic force and moment on the ship are predicted.In this thesis, numerical method for viscous flow by solving RANS equations is applied to simulate the viscous flow around ships in some typical manoeuvring motions in restricted waters. The characteristics of the viscous flow around the manoeuvring ships are captured. By analyzing the flow information, one can get deep insight into the changing mechanism of the hydrodynamic forces on a manoeuvring ship in restricted waters. Moreover, the numeircal method can accurately predict the viscous forces on a manoeuvring ship in restricted waters, demonstrate the changing tendence of the hydrodynamic forces with the factors including the water depth and the distance to bank, as well as the transient characteristics of the hydrodynamic forces. This is theoretically significant and practically useful for research on ship manoeuvring and control in restricted waters.更多还原