船体阻力数值计算在肥大船型球首优化中的应用

以一艘低速肥大型油船为研究对象,设计了三型多参数共18个不同球首。采用荷兰MARIN水池开发的RAPID软件进行船体阻力数值计算,为肥大船型的球首优化提供了必要的基本信息。     

Geometric modelling of bulbous bows with the use of non-uniform rational B-spline surfaces

Nowadays, bulbous bow forms have become a common design feature in most conventional ship designs. The design of a bulbous bow is usually attempted with the use of certain form parameters that are imposed using the designer's experience or regression values that provide the optimum parameters based on experimental tests or computational fluid dynamics (CFD) calculations. In this article, the geometric modelling of a bulbous bow form that complies with a series of parameters is presented. First, a wire model was constructed with cubic B-spline curves that hold certain form parameters that the designer wants to impose. Second, a B-spline surface that fits these splines was mathematically constructed. A review of the influence of the design parameters used on the bulbous bow properties was made. This method could be used prior to numerical optimization of a bulbous bow because different variations of the design can be easily generated. These variations can be tested numerically using CFD software. A practical application example of the method is shown.     

撞角球鼻艏形式和参数变化对阻力影响的研究

通过数值计算及模型试验确定了撞角球鼻艏形式和参数对阻力的影响。针对3个形式各异的球鼻艏方案,开展了CFD计算和模型试验,结果显示:当傅汝德数为0.28时,撞角球鼻艏的剩余阻力系数比无球鼻艏的剩余阻力系数约小20%。以8个主要参数各异的撞角球鼻艏方案为对象,采用CFD技术分析了撞角球鼻艏的参数变化对兴波阻力的影响,并确定了撞角球鼻艏的宽度比和纵向长度比对兴波阻力系数的影响。     

基于CFD的金枪鱼延绳钓渔船球鼻艏形状研究

以49.5 m金枪鱼延绳钓渔船为研究对象,为了得到具有较好阻力性能的球鼻艏,首先设计撞角型球鼻艏,通过CFD方法得到撞角型球鼻艏渔船的阻力性能并与模型试验结果进行比较,两者吻合较好;然后通过改变球艏的伸出长度、形心浸深和体积为该船设计水滴型和S-V上翘型球鼻艏,对水滴型和S-V上翘型球鼻艏形式的船体阻力性能进行数值模拟。通过比较三种不同球鼻艏形式下船体的阻力性能,结果显示:该型延绳钓渔船使用撞角型球鼻艏具有较好的减阻效果。     

基于CATIA二次开发的球首参数化设计

为实现在船舶型线设计中快速生成船舶球首,以船舶球首为研究对象,通过定义控制球首形状的纵向边界线、横向边界线、横剖面形状,设置相关控制参数,以CATIA为开发平台,VB为开发工具,对其进行二次开发,编制球首参数化设计程序,迅速地生成球首三维模型。     

球鼻艏伸出长度对阻力性能的影响

我国作业的众多渔船中,拖网渔船占了多数。为了响应国家节能减排政策,故采取安装合适的球鼻艏以起到减少阻力的作用。文中采用CFD技术,在球鼻艏伸出长度的变化上对拖网渔船进行阻力的比较研究,从中得到适当的球鼻艏使得拖网渔船在设计航速下得到较好的减阻节能效果。     

基于BP网络的球鼻首参数化优化

本文以某集装箱船为研究对象,对降速航行后的球鼻首进行优化。采用Catia建立船体三维模型,为了产生不同形状的球鼻首,选取球鼻特征参数来描述其基本结构;采用拉丁超立方试验抽样方法得到12组不同形状的球鼻首,提出运用非线性拟合能力较强的BP网络构建球鼻首参数和阻力系数之间的关系模型;采用遗传算法对训练后的网络进行极值寻优。结果显示,优化船型的阻力系数显著降低,说明该方法对球鼻首的优化有一定的借鉴意义。     

基于CFD和伴流场优化的肥大型船球鼻艏数值选型研究

在某肥大型船母型船的基础上设计了几种球鼻艏外形方案,基于CFD技术预报了母性船桨盘面处的伴流分布,通过与试验结果的对比分析,检验了数值预报方法的适用性,在此基础上采用该方法预报了不同球鼻艏方案的桨盘面处的轴向伴流,并使用WOF方法来衡量不同球鼻艏方案对应的轴向伴流均匀情况,通过对比分析得到一种伴流分布相对较好的球鼻艏方案.     

船舶碰撞缓冲型球鼻艏概念探讨--球鼻曲率对碰撞的影响

船舶碰撞事故中，被撞油船船侧的破裂会引起严重的海洋污染，故油船双层船壳设计成为防止被撞油船破损的有效措施。但随着海上运输船舶的数目及尺度的日益增大，双层船壳已不能满足防止船侧破损的要求。本文提出了缓冲型球算般的构思。在船舶相撞的过程中，球鼻艏曲率的尖锐程度影响被撞船船侧的损伤程度，故提出并讨论了表征球鼻艏碰撞特性的标志性参数。通过对不同曲率的球鼻艏一系列的碴撞数值仿真计算，详细描述了外形曲率对球鼻艏的变形形态、碰撞力、碰撞力密度及能量吸收的影响，指出船舶采用钝形的球鼻艏能有效减小碰撞时的穿透损伤。     

Design of offshore structures against accidental ship collisions

In this paper, we investigate the damage to offshore platforms subjected to ship collisions. The considered scenarios are bow and stern impacts against the column of a floating platform and against the jacket legs and braces. The effect of the ship–platform interaction on the distribution of damage is studied by modeling both structures using nonlinear shell finite elements. A supply vessel of 7500-ton displacement with bulbous bow is modeled. A comprehensive numerical analysis program is conducted, and the primary findings are described herein. The collision forces from the vessel are compared with the suggested force–deformation curves in the NORSOK code. For collisions with floating platforms we particularly focus on the crushing behavior and potential penetration of the bulbous bow and stern sections into the cargo tanks or void spaces of semi-submersible platforms. For fixed jacket platforms we investigate whether jacket braces can penetrate into the ship without being subjected to significant plastic bending or local denting.Adequate treatment of the relative strength between the interacting bodies is especially relevant for impacts with high levels of available kinetic energy, for which shared energy or strength design is aimed at. Simplifying one body as rigid quickly leads to overly conservative and/or costly solutions, and is in some cases non-conservative.The numerical analysis is used to develop a novel pressure–area relation for the deformation of the bulbous bow and stern corners of the supply vessel. Procedures for strength design of the stiffened panels are discussed. Refined methods and criteria are proposed for strength design of platforms, including both floating and jacket structures. The adequacy of the NORSOK design guidance for collisions against jacket legs is evaluated. The characteristic strength of a cylindrical column is used to develop a novel criterion for the resistance to local denting from stern corners and bulbous bows.     

Optimization of bow shape for a non ballast water ship

In this research,a commercial CFD code ＂Fluent＂ was applied to optimization of bulbous bow shape for a non ballast water ships（NBS）.The ship was developed at the Laboratory of the authors in Osaka Prefecture University,Japan.At first,accuracy of the CFD code was validated by comparing the CFD results with experimental results at towing tank of Osaka Prefecture University.In the optimizing process,the resistances acting on ships in calm water and in regular head waves were defined as the object function.Following features of bulbous bow shapes were considered as design parameters： volume of bulbous bow,height of its volume center,angle of bow bottom,and length of bulbous bow.When referring to the computed results given by the CFD like resistance,pressure and wave pattern made by ships in calm water and in waves,an optimal bow shape for ships was discovered by comparing the results in the series of bow shapes.In the computation on waves,the ship is in fully captured condition because shorter waves,λ/Lpp 0.6,are assumed.     

舰艇球鼻首金属导流罩的结构声学设计

针对舰艇球鼻首为声呐服务的主要功能,为提高其透声性能,对新型金属双壳导流罩的声学设计进行研究。研究从金属单层板和双层板的透声基本原理开始,通过计算和试验分析双层平板的透声状况,并选取钛合金材料作为新型导流罩的建造材料,用理论公式和有限元建模两种方法计算整体球鼻首的透声状况。为保证真实性能,建造实体模型对其进行了试验验证。通过此项研究验证了这种双壳结构的金属球鼻首导流罩具有良好的透声性能,实验结果满足声呐的工作要求。     

基于CFD的船舶球首型线自动优化

在满足排水量及航速要求情况下设计出性能优良的船体型线,降低船体阻力、节能降耗是造船界一直所追求的目标。船舶球首的大小、位置和形状对船体兴波影响非常大,因此文章通过船型参数化融合方法,生成一系列球首型线,并以兴波阻力最小为目标,采用遗传算法实现球首型线的自动优化。将上述方法应用于某集装箱船球首型线的自动优化,并进行船舶静水阻力实验,实验表明优化船型在设计航速附近总阻力降低明显,说明文中采用的基于CFD船型自动优化方法是可行的。     

缓冲型球艏的艏柱设计计算分析

依据缓冲球艏设计要求,提出棱柱型艏柱设计方案,运用有限元分析软件LS-DYNA对采用传统艏柱与棱柱型艏柱结构的12 000 t油船进行船艏碰撞的仿真分析,发现棱柱型艏柱结构比传统艏柱结构球艏更易被压溃.     

舰艇新型球鼻首结构设计探索

从材料选型入手对舰艇新型球鼻首的结构设计进行探索,研究结构和声学性能要求,提出性能优良的球鼻首结构方案,以备新型舰艇球鼻首的实际建造和后续发展.     

舰船球鼻首结构试验研究

作为船体中比较特殊的双曲结构,舰船首部的球鼻首相关的结构试验规范很少.为探索试验方法,开展了一系列的实物试验研究,通过合理实施途径进行试验,得到直接测试数据,并验证设计的合理性.针对舰船球鼻首进行的3项试验:静态压力试验、抛落试验和爆炸试验,介绍了试验前的准备工作、测点布置、过程和响应情况,为特殊结构的设计和试验规范的制定打下基础.     

特种材料球鼻艏抗冲击特性数值研究

为探讨球鼻艏结构的抗冲击性能,采用数值手段对典型球鼻艏结构进行一体化建模,基于Abaqus的声固耦合法模拟水下非接触爆炸载荷与球鼻艏结构的相互作用,提取设计工况下的球鼻艏典型部位的冲击响应结果。结果表明：钛合金材料极大提高了球鼻艏结构的局部抗冲击性能,但在遭受水下非接触爆炸载荷时,仍出现了明显的塑性变形;球鼻艏底部钢结构由于采用纵横肘板进行支持,具有优异的安全性;随着冲击因子的增加,球鼻艏结构的应力近似呈线性增长,而塑性应变曲线随着冲击因子的增加呈指数曲线增加。     

低速肥大型船舶球首型线选优软件的开发与应用

介绍了低速肥大型船舶球首型线选优软件的构成,功能和使用方法。以４型船２９个球首方案为例,验证了软件的可行性;同时,应用该软件分析了球首主要参数对首部流线及船舶阻力的影响。     

用上翘型球首改善压载试航状态阻力性能

若干新船的模型阻力试验中~(［１,２］),尽管压载试航状态的吃水和排水量均比满载状态小得多,然而将试验结果换算到实船,却出现了试航状态的有效功率大于满载状态的意外情况。对此,设计部门和船东都不能接受。本文介绍一种上翘型球首,将它替代原型船首,可使试航状态的有效功率显著地降至满载状态以下。     

LPC快艇加装声呐球鼻模型阻力试验

对LPC快艇加装声呐球鼻艏船进行模型阻力试验,设计了适合此快艇加装声呐球鼻艏的5种方案.试验得到5种方案的19种状态的船模试验基本参数,在换算成实船后得到实船总阻力曲线图、实船有效功率曲线图和实船剩余阻力曲线图.船模阻力试验结果表明,加装此5种球鼻后,船模总阻力增加都较小,且在设计航速上仍有较好的耐波性和稳定性,综合船...