Experimental Investigation of the Resistance Performance and Heave and Pitch Motions of Ice-Going Container Ship Under Pack Ice Conditions

In order to analyze the ice-going ship’s performance under the pack ice conditions, synthetic ice was introduced into a towing tank. A barrier using floating cylinder in the towing tank was designed to carry out the resistance experiment. The test results indicated that the encountering frequency between the ship model and the pack ice shifts towards a high-velocity point as the concentration of the pack ice increases, and this encountering frequency creates an unstable region of the resistance, and the unstable region shifts to the higher speed with the increasing concentration. The results also showed that for the same speed points, the ratio of the pack ice resistance to the open water resistance increases with the increasing concentration, and for the same concentrations, this ratio decreases as the speed increases. Motion characteristics showed that the mean value of the heave motion increases as the speed increases, and the pitch motion tends to increase with the increasing speed. In addition, the total resistance of the full-scale was predicted.     

GPU-Based DEM Simulations of Global Ice Resistance on Ship Hull During Navigation in Level Ice

The ice resistance on a ship hull affects the safety of the hull structure and the ship maneuvering performance in icecovered regions.In this paper,the discrete element method(DEM)is adopted to simulate the interaction between level ice and ship hull.The level ice is modeled with 3D bonded spherical elements considering the buoyancy and drag force of the water.The parallel bonding approach and the de-bonding criterion are adopted to model the freezing and breakage of level ice.The ship hull is constructed with rigid triangle elements.To improve computational efficiency,the GPU-based parallel computational algorithm was developed for the DEM simulations.During the interaction between the ship hull and level ice,the ice cover is broken into small blocks when the interparticle stress approaches the bonding strength.The global ice resistance on the hull is calculated through the contacts between ice elements and hull elements during the navigation process.The influences of the ice thickness and navigation speed on the dynamic ice force are analyzed considering the breakage mechanism of ice cover.The Lindqvist and Riska formulas for the determination of ice resistance on ship hull are employed to validate the DEM simulation.The comparison of results of DEM,Lindqvist,and Riska formula show that the DEM result is between those the Lindqvist formula and Riska formula.Therefore the proposed DEM is an effective approach to determine the ice resistance on the ship hull.This work can be aided in the hull structure design and the navigation operation in ice-covered fields.     

Numerical Simulation and Experimental Research on Wake Field of Ships Under off-Design Conditions

Different operating conditions (e.g. design and off-design) may lead to a significant difference in the hydrodynamics performance of a ship, especially in the total resistance and wake field of ships. This work investigated the hydrodynamic performance of the well-known KRISO 3600 TEU Container Ship (KCS) under three different operating conditions by means of Particle Image Velocimetry (PIV) and Computational Fluid Dynamics (CFD). The comparison results show that the use of PIV to measure a ship’s nominal wake field is an important method which has the advantages of being contactless and highly accurate. Acceptable agreements between the results obtained by the two different methods are achieved. Results indicate that the total resistances of the KCS model under two off-design conditions are 23.88% and 13.92% larger than that under the designed condition, respectively.     

Study on Flow Field Around Vertical Breakwater Under Different Overtopping Conditions Based on Numerical Simulation

A numerical wave flume is constructed based on the Reynolds Averaged Navier-Stokes (RANS) equations with turbulence closure by a modified k-ε model to study the viscous interactions of waves with vertical breakwaters for different overtopping cases. The governing equations,the turbulence model,boundary conditions,and solution method for the numerical wave flume are introduced briefly. The reliability of the numerical wave flume is examined by comparing the numerical results with the experimental measurement...     

Full-Scale Numerical Simulation of the Local Scour Under Combined Current and Wave Conditions Based on Field Data

The monopile is the most common foundation to support offshore wind turbines. In the marine environment, local scour due to combined currents and waves is a significant issue that must be considered in the design of wind turbine foundations. In this paper, a full-scale numerical model was developed and validated based on field data from Rudong, China. The scour development around monopiles was investigated, and the effects of waves and the Reynolds number Re were analyzed. Several formulas for p...     

Numerical Simulation of Icing on Nrel 5-MW Reference Offshore Wind Turbine Blades Under Different Icing Conditions

Offshore wind energy resources are operational in cold regions, while offshore wind turbines will face the threat of icing. Therefore, it is necessary to study icing of offshore wind turbines under different icing conditions. In this study, icing sensitivity of offshore wind turbine blades are performed using a combination of FLUENT and FENSAP-ICE software, and the effects of liquid water content (LWC), medium volume diameter (MVD), wind speed and air temperature on blade icing shape are analyzed by two types of ice, namely rime ice and glaze ice. The results show that the increase of LWC and MVD will increase the amount of ice that forms on the blade surface for either glaze ice or rime ice, and an increase of MVD will expand the adhesion surface between ice and blade. Before reaching the rated wind speed of 11.4 m/s, it does not directly affect the icing shape. However, after reaching the rated wind speed, the attack angle of the incoming flow decreases obviously, and the amount of ice increases markedly. When the ambient air temperature meets the icing conditions of glaze ice (i.e., −5°C to 0°C), the lower the temperature, the more glaze ice freezes, whereas air temperature has no impact on the icing of rime ice. Compared with onshore wind turbines, offshore wind turbines might face extreme meteorological conditions, and the wind speed has no impact on the amount of ice that forms on the blade surface for most wind speeds

     

艏艉线型优化对船舶阻力性能的影响

为提高母型船阻力性能,以船体阻力性能为优化对象,基于改造母型船法,研究船舶球鼻艏以及船尾线型的改变对船舶阻力性能的影响.采用高度集成化的Tribon系统、可视化绘图软件Auto CAD及CFD(Computational Fluid Dynamics)通用前处理软件ICEM联合建模的方法来建立船体模型.通过模拟计算结果与实验值的对比分析,验证CFD技术在船舶阻力性能预报中的合理性和有效性.通过对比3种不同球鼻艏时的船体阻力得知:从阻力性能方面考虑,对于低速丰满型船舶选用普通型球鼻艏以及中高速船舶采用上翘型球鼻艏均可以获取较好地减阻效果.同时比较不同航速下尾部线型对船体总阻力的影响表明,选优后的方形尾在相同的航速下阻力低、消耗的功率小、形状效应小、黏压阻力和摩擦阻力也相对较小.     

Numerical Simulation of Bohai Oil Spill in the Winter Sea Ice Period

The Bohai Sea is a seasonal icy sea area that has the lowest latitude of any sea experiencing icing in the northern hemisphere, and simulation studies on oil spills during its sea ice period are the key to analyzing winter oil spill accidents. This study applied the three-dimensional free surface to establish a high-resolution hydrodynamic model and simulate tidal distributions in the Bohai Sea. Then, the oil spill model of the open sea area and thermodynamic model were combined to establish a numerical model for the Bohai oil spill during the winter sea ice period. The hydrodynamic model and sea ice growth and melting model were verified, and the parameters were adjusted based on the measured values, which indicate that the numerical model established in this paper is of high accuracy,stability and ubiquity. Finally, after checking the calculations repeatedly, the diffusion coefficient for the Bohai Sea was determined to be 1.0×10~(–7 )m~2/s. It is better that the comprehensive weathering attenuation coefficient is lower than that of a non-winter oil spill, with 1.3×10~(–7 )m~2/s being the most appropriate coefficient. This study can provide the reliable technical support for the operational safety and reduction in losses caused by winter oil spill accidents for the petroleum industry.     

极地冰藻极端海冰生境适应机制及其受气候变化的影响

冰藻是南北极海冰生物群落中最主要的组成部分,通过固定和输出碳、吸收养分、生产释放氧气和有机化合物,推动高纬度生态系统的生物地球化学循环,在南北极海洋生态系统中发挥着重要作用.从宏观到微观综述了近年来在海冰栖息环境特征、冰藻种类组成和群落结构、冰藻对极端环境的适应机制以及气候变化对海冰环境和冰藻的影响等方面的研究进展,并...     

东营港扩建工程码头船舶靠离泊数值模拟研究

通过对东营港扩建工程码头2种设计代表船型的进出港和靠离泊操纵数值模拟,分析风、浪、流等环境条件对船舶操纵的影响,论证船舶进出港和靠离泊的安全性,验证水域布置的合理性,为工程建设、船舶操纵和港航管理提供科学依据。     

复杂地形下海浪数值模式的特征线计算格式

LAGFD-WAM海浪数值模式是一种第三代海浪数值模式，通过求解波数谱平衡方程，并考虑风输入、波浪破碎耗散、底摩擦耗散、波波非线性相互作用和波流相互作用等源函数，模拟波数空间下的海浪方向谱，并依此获得海浪的波高、周期和平均波向。该模式的一个显著特点是采用特征线嵌入格式求解海浪的传播。在进行浅水区域的海浪模拟时，特征线嵌入格式的数值计算方案是否合理对海浪数值模拟结果产生直接的影响。为此LAGFD-WAM海浪数值模式提出了一种新的特征线混合数值计算格式，并应用于浅水海浪数值模拟。结果表明，采用该计算方法，能够使数值模拟结果与实测结果很好符合。     

某无人水下航行器阻力特性数值模拟

基于FLUENT流体CFD软件,对带鳍舵布局的某无人水下航行器进行了阻力特性数值模拟.选择了合理入口边界条件、出口边界条件、压力与速度的耦合求解方法.数值模拟结果与风洞实验对比表明:该方法对无人水下航行器的阻力特性的预测精度较高,且对流场的显示更加详细、直观.所取得的研究成果对带鳍舵布局无人水下航行器的外形设计具有一定...     

潮汐机组双向发电性能数值模拟研究

为了提高潮汐机组双向发电的综合性能,研究了采用单侧、双侧导叶两种形式对贯流式潮汐机组水力性能的影响。基于N-S方程和RNG k-ε湍流模型,采用SIMPLIC算法,分别对采用单侧导叶、双侧导叶方案的水轮机全流道进行了三维定常数值模拟,分析了正向、反向发电时水轮机的内部流动状况。对不同导叶开度下水轮机的水头、流量和力矩等参数进行计算。结果表明,采用双侧导叶时,虽然正向发电效率有所降低,但反向发电的效率大大提高。     

Numerical Simulation on Oscillation-Sliding-Uplift Rock Coupled Motion of Caisson Breakwater Under Wave Excitation

Corresponding to the sliding and the overturning failure, the elementary motion modes of caisson breakwater include the horizontal-rotational oscillation coupled motion, the horizontal sliding-rotational oscillation coupled motion, the horizontal vibrating-uplift rocking coupled motion, and the horizontal sliding-uplift rocking coupled motion. The motion mode of a caisson will transform from one to another depending on the wave forces and the motion behaviors of the caisson. The numerical models of four motion modes of caisson are developed, and the numerical simulation procedure for joint motion process of various modes of caisson breakwater under wave excitation is presented and tested by a physical model experiment . It is concluded that the simulation procedure is reliable and can be applied to the dynamic stability analysis of caisson breakwaters.     

Numerical Simulation on Oscillation-Sliding-Uplift Rock Coupled Motion of Caisson Breakwater Under Wave Excitation

Corresponding to the sliding and the overturning failure, the elementary motion modes of caisson breakwater include the horizontal-rotational oscillation coupled motion, the horizontal sliding-rotational oscillation coupled motion, the horizontal vibrating-uplift rocking coupled motion, and the horizontal sliding- uplift rocking coupled motion. The motion mode of a caisson will transform from one to another depending on the wave forces and the motion behaviors of the caisson. The numerical models of four motion modes of caisson are developed, and the numerical simulation procedure for joint motion process of various modes of caisson breakwater under wave excitation is presented and tested by a physical model experiment. It is concluded that the simulation procedure is reliable and can be applied to the dynamic stability analysis of caisson breakwaters.     

冰盖下水流纵向紊动特性的试验研究

冬季河流封冻后,水体表面出现固体冰盖,使得过水断面的湿周增大,水力半径减小,从而导致了水流结构和紊动水体对河底附加切应力的改变。进行冰盖下水流纵向紊动特性试验研究对进一步探讨冰盖下的紊流冲刷具有一定的指导意义。本文借助室内模拟试验,对不同流速、水深、冰盖糙率等条件下的冰盖下水流垂线流速及紊动强度进行了观测与分析,得出了以下结论:在水流条件基本一致的情况下,冰盖下水流纵向紊动强度比明流大;且随冰盖糙率的增大,冰盖下水流的纵向紊动强度逐渐增大。     

水平轴潮流能水轮机水动力数值模拟研究

针对水平轴潮流能水轮机,对其进行了力学分析并运用CFD方法对其水动力性能进行了仿真计算。比较了定常计算与非定常计算结果的区别,运用定常计算(MRF)方法得到了表现水轮机性能的功率、扭矩和推力特性曲线,分析了水轮机在不同尖速比时的表现。对水轮机模型进行了拖曳水池试验,并与仿真数据进行了比对分析,两者吻合度较好,并分析了试验过程中出现的在尖速比较大时功率系数衰减的现象,表明CFD方法对水轮机的工程实践有着指导意义。得到了尾流场的速度云图、流线分布图与衰减曲线,结果表明相对于水轮机的直径,受到其影响后的流场存在扩张现象。分析了水轮机后不同位置处的流场衰减情况,结果显示,随着水轮机后轴向距离的不同其速度恢复差别很大,对于今后潮流能水轮机的大规模布置方式研究提供了依据。     

Numerical Investigations on Hydrodynamic Performance of An Open Comb-Type Breakwater Under Medium Water Levels

China Ocean Engineering - The comb-type breakwater (CTB) has been proposed and investigated in recent years due to its advantages in terms of deep-water adaptability, material saving and water...     

Numerical Study on Scale Effect of Form Factor for DTMB5415, KCS,KVLCC2, and 4000TEU Container Ship

China Ocean Engineering - Four ships, a twin-propeller naval ship, two single-propeller container ships, and a single-propeller very large crude carrier (VLCC), were studied to investigate the...