垂直及斜出水流场的二维及三维TR-PIV试验

本文对钝头回转体垂直及斜出水流场采用TR-(Time-Resolved)PIV技术进行测量,并对斜出水流场进行3D-Stereo PIV(三维体视 PIV)测量.文中介绍了测试技术及测量结果,揭示了出水过程中流动结构及其演变,展示了TR-PIV技术对具有瞬态历程特征的出水流场研究的适应性.     

Comparative measurements on the flow structure of a marine propeller wake between an open free surface and closed surface flows

In order to investigate the effects of a free surface on the wake behind a rotating propeller, experiments were carried out in a circulating water channel for two cases: one with an open free surface and one with a closed free surface covered by a rigid plate. Four hundred instantaneous velocity fields were measured using a two-frame particle image velocimetry (PIV) technique at four different blade phases. These were ensemble-averaged to investigate the time-averaged flow structure in the near-wake region. For a surface ship, the flow behind the propeller is influenced by the hull wake and the free surface. The phase-averaged mean velocity fields show the potential wake and the viscous wake formed by the boundary layers developed on the blade surfaces. The interaction between the bilge vortices and the incoming flow along the ship’s hull deforms the wake structure. Tip vortices are generated periodically, and the slipstream contraction occurs in the near-wake region. The free surface was found to affect the axial velocity component and vortex structure behind the propeller. As the flow goes downstream, the tip and trailing vortices dissipate due to turbulent diffusion and active mixing with adjacent vortices.     

2 500 TEU集装箱船的总体设计

随着人们对环境保护的日益重视,越来越多的法规对船舶设计提出更高的环保要求.通过2 500 TEU集装箱船的总体设计,对装载和破舱稳性等总体性能等进行了设计计算,使该船布置合理紧凑,各项指标达到国际先进水平.但燃油舱划分和分布要满足有关新规划,还需作适当调整.     

530TEU集装箱船的轴系设计

轴系是船舶动力装置的重要组成部分之一,轴系工作状态欠佳将引起主机油耗增加,工况恶化,甚至会导致船舶振动,影响船舶的正常航行。轴系的结构种类很多,目前我国海洋船舶广泛采用的是常规螺旋桨推进装置轴系,即尾机型,采用固定螺距螺旋桨。中纵布置的单轴系。下面以530TEU集装箱船的轴系设计为例,对此种轴系的设计作一简要介绍。     

6750箱集装箱船非线性波激振动和颤振响应分析

本文采用三维时域非线性水弹性方法分析了一艘6750箱集装箱船的水弹性响应以及运动和垂向弯矩特征。通过考虑入射波力、静水恢复力、砰击效应的非线性,研究了在恶劣海况下船体的非线性运动和垂向弯矩响应,同时分析了波激振动及颤振对垂向弯矩的影响。数值计算结果表明:(1)非线性入射波力对运动的影响较小,但是对垂向弯矩的影响较大,使得其有明显的倍频成分,同时中垂弯矩显著大于中拱弯矩。另外,非线性入射波力也引起了明显的非线性波激振动;(2)非线性静水恢复力对运动和载荷的影响均较大,但是没有引起明显的非线性响应。非线性计算的垂荡响应小于线性结果,而纵摇和垂向弯矩响应大于线性结果;(3)砰击效应对运动的影响较小,但对垂向弯矩的影响较大,砰击效应引起了显著的船体弹性高频振动,增大了载荷幅值,但是其引起的合成中垂和中拱幅值相差不大;(4)非线性水动力的作用主要引起垂向弯矩的倍频响应,包括倍频可能引起的二节点垂向弯矩弹性共振,而砰击效应主要引起船体二节点垂向弯矩共振;(5)本文的非线性水弹性响应计算结果与Kim给出的数值计算结果吻合很好。     

多块结构化网格在含附体水面船模粘性流场数值计算中的应用

本文使用RANS方程和剪切应力输运k-ω模型求解含附体的水面船舶粘性流场.整个计算域被分成很多区块,各个区块单独生成结构化网格,在包含不同附体部件的区块之间,网格是不匹配的,交界面处各流场变量由插值计算传递.计算中没有考虑自由液面的影响.从最后计算得到的桨盘面伴流分布结果来看,数值计算较好地反映了桨盘面流场的特征.     

平板湍流边界层流向—法向平面发卡涡的PIV实验研究

湍流边界层流动精细涡结构的分析对于水下航行体表面减阻乃至降噪机理的深入研究都具有重要意义.文章应用粒子图像测速技术(PIV),对Reθ=1 743和5 400时的平板湍流边界层的流向—法向平面流场进行了测试研究.一方面,直接对瞬时速度场精细涡结构进行提取分析,通过Galilean分解和λci准则识别出流向—法向平面中的发卡涡及发卡涡包.研究表明,发卡涡和雷诺应力的分布特征具有高度相关性;发卡涡包产生了流向动量的法向不规则分层分布特征.另一方面,文中通过对500个瞬时速度场子样进行时间平均分析,获得了不同雷诺数下平均速度以及湍流度分量的法向分布规律.此外,文中还对发卡涡的几何尺寸和漩涡强度λci进行了统计分析.研究表明,在y+＜50范围内无量纲化的漩涡强度λciδ/uт沿法向迅速衰减,且在不同雷诺数下变化曲线基本一致;在y+ ＞50后λciδ/uт衰减平缓,且低雷诺数下的值较大.     

Investigation of turbulent flows in a waterjet intake duct using stereoscopic PIV measurements

Stereoscopic particle image velocimetry measurements were made in a wind tunnel using a prototype waterjet model. The main wind tunnel provided the vehicle velocity and a secondary wind tunnel was set up as the waterjet propulsion model. Pressure distributions along the ramp and lip sides inside the duct were measured for three jet velocity to vehicle velocity ratios. Three-dimensional velocity fields were obtained at the intake entrance and the nozzle exit of the waterjet system. The flow into the duct was faster in the lip region than on the ramp side. Because of the variation in intake geometry from a rectangular to a circular section and because of the sudden curvature change on the lip side, a pair of counter-rotating vortices was observed in the mean velocity field at the nozzle exit. In addition, the turbulent kinetic energy correlated with the vortex pair was stronger on the lip side than in other areas. Dominant large-scale structures were extracted by using a snapshot proper orthogonal decomposition analysis. It was found that most of the turbulent kinetic energy was attributed to at least three vortices near the nozzle exit. This detailed three-dimensional velocity field will be useful for the verification of CFD simulations applied to the waterjet system.     

Numerical analysis on free surface waves and stern viscous flow of a ship model

This paper deals with numerical techniques for computing the viscous flow past a ship hull with and without a free surface using a Reynolds-averaged Navier-Stokes solver with global conservation. In the first technique, a coarse grid is used to find an approximate solution to the free surface problem. Interpolation of a fine grid is subsequently carried out, and a more exact solution, particularly in the boundary layer and wake, is obtained. In the second technique, a modified Baldwin-Lomax model is introduced to compute the viscous flow with and without a free surface. These numerical techniques are applied to simulations of the flow around a Series 60 and an SR196C ship model. The results are compared with measurement data, and the usefulness of the numerical techniques is demonstrated.     

通气超空泡内部流场PIV测试方法

研究通气超空泡内部流场的PIV测试方法。通过合理选择空心玻璃珠示踪粒子,利用流化床粒子布撒装置并合理设计通气管路解决了示踪粒子通入问题,采用二维PIV测试系统实现了水洞实验的通气空泡内部流场测试,获得了通气超空泡内部清晰的粒子影像,经数据处理得到了流场速度及涡量分布。实验表明采用PIV技术可实现对通气超空泡内部流场的测试,测试结果能够揭示流场的结构特征,可以为空泡流理论的深入研究提供实验依据,所给出的超空泡内部流场PIV测试实现方法可供其它相关研究借鉴和参考。     

通气超空泡内部流场的PIV实验图像处理

PIV测试是流体动力学实验研究的重要方法之一,可以成为通气超空泡内部流场结构实验研究的有效手段。通过水洞实验利用PIV对通气超空泡内部流场进行测试时,激光在气液两相界面处会发生折射,导致实验图像变形和失真。文章分析了激光在空化流场中各相界面的折射特性和PIV实验图像的变形规律;在此基础上,推导了图像变形的分析计算式,给出了通过原始流场图像获取真实流场图像的还原处理方法;编制了图像还原计算程序,并对原始PIV图像进行了处理,得到了反映真实空泡内部流场结构的图像。     

Investigation on the vortex structure of propeller wake influenced by loading on the blade

The vortex structure of the wake behind a marine propeller was investigated in terms of loading variation by using particle image velocimetry. One hundred and fifty instantaneous velocity fields were ensemble averaged to study the spatial evolution of the wake and the behavior of the tip vortices in the region ranging from the trailing edge to one propeller diameter downstream. The trailing vorticity was found to be related to the radial velocity jump, and the viscous wake was affected by the boundary layers developed on the blade surfaces. A vortex identification method using the swirling strength was employed to extract the location of the tip vortex. The loading on the blade made a clear difference to the contraction angles. Slipstream contraction occurred in the very near wake region, and unstable oscillation occurred because of reduced interaction between the tip vortex and the wake sheet behind the maximum contraction point for each loading condition. The maximum tangential velocity around the tip vortex center revealed the average radius of its core, which was used for calculating the vortex strength. Additionally, variation of the average radius of tip vortices with the change of blade loading was related to vortex tube stretching in the wake region. The nearly constant vortex strength continued up to one diameter downstream for light loading and design loading conditions.     

Simulation of unsteady free-surface flow around a ship hull using a fully coupled multi-phase flow method

An accurate, efficient algorithm for solving free surface flows around ship hulls is described. Accuracy is achieved using a compressive advection discretization which maintains a sharp free surface interface representation without relying on a small time step. Efficiency is obtained using a solution algorithm which implicitly couples velocity, pressure, and volume fractions. The algorithm has been implemented in a computational fluid dynamics code called CFX and is validated by means of a comparisonwith experimental data of benchmark cases in both steady and transient conditions.     

三维圆柱体绕流数值模拟流场选择及网格划分

文章通过数值模拟结果确定适合的三维圆柱体绕流流场的尺寸,采用不同的计算流体力学(CFD)软件对有限元模型进行网格划分,对比网格划分质量的优劣,选择适合数值模拟的软件CFX。确定采用的网格形式为六面体网格(Hex8)以及流场不同部分网格的尺寸。圆柱绕流展向各截面平均压力系数沿周向无明显变化,脉动压力系数变化显著,绕流后的旋涡发放形式具有明显的三维特性的数值模拟结果验证了本文的流场选择和网格化分尺度的合理性。     

A reactive container rerouting model for container flow recovery in a hub-and-spoke liner shipping network

This paper focuses on the container rerouting due to a disruption, aims at making the optimal container flow recovery plan for the affected liner shipping company. First, we make the initial effort to bring up with a basic framework of disruption management for liner shipping. Second, we present a compact integer linear programming model for addressing the container rerouting problem under the proposed framework in a hub-and-spoke liner shipping network, based on a given recovery vessel schedule that determines to omit a port of call. Other shipping companies’ services and other modes (roadway, railway, and airline) as candidate alternative means to transport the miss-connected containers are also incorporated in the proposed model. The container flow recovery plan would select the optimal alternative paths for the miss-connected containers balancing the trade-off between container transport costs and delivery delay penalty costs. Finally, a case study from a global liner shipping company is investigated and the computational results indicate the model can be solved effectively and efficiently for the real-scale problem. Thus, the proposed approach in this paper can supply real-time decision support tool for the liner shipping operators on handling the process of container flow recovery.     

螺旋桨/船体粘性流场的整体数值求解

螺旋桨和船体是相互作用的,孤立地对螺旋桨或船体流场进行数值模拟均无法有效地对它们的相互影响进行研究.本文采用周向平均的混合面处理方法,实现了螺旋桨/船体流场的整体计算,计算结果和试验数据进行了比较,表明该方法能很好地模拟螺旋桨和船体之间的相互影响,从而揭示了真实螺旋桨和船体之间相互干扰的内在规律.本文研究结果为研究螺旋桨和船体相互影响提供了更加精确和实用的研究手段.     

离心泵叶轮进口前非定常流动研究

以一离心泵为对象,进行模型泵叶轮进口前非定常流动的PIV试验及数值模拟。基于PIV试验结果可知,在不同流量工况下,吸入管内均存在着较为强烈的预旋流动,预旋流的方向与叶轮旋转方向一致。且泵偏离设计流量工况越大、与叶轮距离越近,预旋流的绝对速度越大。同时,应用数值模拟的方法,详细分析了吸入管内部流场中涡线、压力脉动等的非定常变化,得出在小流量工况下,吸入管内非定常预旋流动将会引起与叶轮转频较为接近的压力脉动,从而对整个泵系统造成严重危害。     

码头前系泊船舶撞击速度研究

采用时域数值模型,对横浪作用下码头前系泊船舶的运动响应进行了研究,分析了波高、周期、水深、船舶尺度及码头型式等因素对撞击速度的影响.结果表明:当波浪周期小于般舶自振周期时,撞击速度随波高的增加线性增长;波浪周期越大,撞击速度越大;船舶装载度(吃水)越小,撞击速度越大;墩式码头(无限开敞水域)中系泊船舶的撞击速度大于岸壁...     

杂货船改装成集装箱船的改装技术探讨

从船舶改装设计技术、建造技术等方面进行研究,结合中国修船特点,以目标杂货船改装成集装箱船为例,试图通过调研、资料收集消化,进行实船试验,探求关键技术及其解决方法。     

粘流方法的螺旋桨尾流场数值分析(英文)

The computational fluid dynamics(CFD) method is used to numerically simulate a propeller wake flow field in open water.A sub-domain hybrid mesh method was adopted in this paper.The computation domain was separated into two sub-domains,in which tetrahedral elements were used in the inner domain to match the complicated geometry of the propeller,while hexahedral elements were used in the outer domain.The mesh was locally refined on the propeller surface and near the wake flow field,and a size function was used to control the growth rate of the grid.Sections at different axial location were used to study the spatial evolution of the propeller wake in the region ranging from the disc to one propeller diameter(D) downstream.The numerical results show that the axial velocity fluctuates along the wake flow;radial velocity,which is closely related to vortices,attenuates strongly.The trailing vortices interact with the tip vortex at the blades’ trailing edge and then separate.The strength of the vortex shrinks rapidly,and the radius decreases 20% at one diameter downstream.