Energy coefficients for a propeller series

The efficiency for a propeller is calculated by energy coefficients. These coefficients are related to four types of losses, i.e. the axial, the rotational, the frictional, and the finite blade number loss, and one gain, i.e. the axial gain. The energy coefficients are derived by use of the potential theory with the propeller modelled as an actuator disk. The efficiency based on the energy coefficients is calculated for a propeller series. The results show a good agreement between the efficiency based on the energy coefficients and the efficiency obtained by a vortex-lattice method.     

快速转向推进器推力优化分配研究

随着船舶推进技术的不断发展,动力定位船舶将更多地使用快速转向推进器以提高其定位性能。快速转向推进器的使用将引入大角度变化率,这会造成优化分配求解域明显的非凸性,给优化问题的求解带来了挑战。针对装备快速转向推进器的动力定位船舶,运用区域外切近似法对其推力分配的非凸性问题进行了凸化,采用增广拉格朗日乘子法对控制力进行了优化分配。仿真结果表明:推荐的凸化处理方法能有效地解决推力分配的非凸问题,分配算法可以充分利用快速转向推进器的机械性能优势,寻找更优的可行解,从而显著地减少动力定位船舶的能耗,提高其定位性能。     

带有柔性阻流器的海底管道冲刷防护试验研究

从管道尾流区泥沙颗粒的受力平衡着手,探讨了管道冲刷的临界压力差。在此基础上,提出了一种防止或减少管道冲刷的新方法,即在管道下方安装柔性阻流器。通过物理模型试验,研究了单向恒定流及规则波作用下,柔性阻流器对管道两侧床面压力、冲刷深度的影响。试验结果表明:柔性阻流器的安装能明显减小管道两侧床面的压力差。在单向恒定流作用下,管道的冲刷深度随阻流器长度的增加而减小;当阻流器达到临界长度时,冲刷消失。规则波时,因阻流器的扰动作用,冲刷深度有所增加;但随阻流器长度的增加,其扰动作用减小,对床面的防护作用增加,因而冲刷深度减小。     

Design of wake-adapted contra-rotating propellers for high-speed underwater vehicles

Based on the lifting-surface vortex lattice model, a numerical design method of wake-adapted contra-rotating propellers (CRPs) for high-speed underwater vehicles is proposed. According to the given radial circulation distribution, the method can use prescribed camber line shapes to design maximum cambers and pitches of blade sections by controlling circulation at the leading edge, which makes the chordwise distribution of blade loading similar to that of NACA a = 0.8. It also can be performed under prescribed chordwise circulation distributions, where camber line shape and blade section pitch are designed. The Newton–Raphson iterative algorithm is utilised in the design of the pitch and camber. The radial circulation distribution of a set of CRPs for an underwater vehicle is used to redesign CRPs by the proposed method, and the design results are then validated via numerical simulations by solving the Reynolds-averaged Navier-Stokes equations. The results indicate that the proposed method is suitable for the design of CRPs with tapered hubs and skewed blades, and it also exhibits good mesh convergence. The CRPs designed with the given camber line shape and the given chordwise loading distribution both have relatively uniform pressure distributions, with the latter being superior.     

Design optimisation of Propeller Boss Cap Fins for enhanced propeller performance

Economic pressures and regulatory requirements have brought about a great interest in improving ship propulsion efficiency. This can be exercised by installing Energy Saving Devices (ESD) such as Propeller Boss Cap Fins (PBCF). This paper demonstrates an approach for optimising PBCF by using Computational Fluid Dynamics (CFD) analysis. The conducted Reynolds-averaged Navier-Stokes (RANS) CFD open water model tests were validated by comparison with experimental data until the simulation was deemed satisfactory within the capabilities and limitations of the model. A design and optimisation procedure was defined to analyse the impact of ESDs on propeller efficiency and then used to evaluate the influence of alternative geometric parameters and locations of the PBCF on the hub. This analysis was done at full scale using high fidelity CFD-based RANS methods. Outcomes of the study include a design and optimisation process that can be used for the analysis of other ESDs on the market. The influences of various PBCF geometry were examined with optimal solutions presented for the analysis case. Results indicated a net energy efficiency improvement of 1.3% contributing to a substantial minimisation of cost and energy consumption. A reduction in the hub vortex was also clearly identified and presented.     

Test method of cavitation erosion for marine coatings with low hardness

Rudders of large container ships are easily affected by cavitation, which is well known to be induced by significant axial flows behind a propeller and discontinuities in the rudder. Among several methods to prevent or reduce the cavitation erosion occurred in the rudder, painting is gaining a lot of attention because it can be employed easily and cheaply. To conduct erosion tests properly, the simulation of heavily erosive cavitation is necessary. This can be generated using an inclined propeller dynamometer in the medium-size cavitation tunnel of MOERI (Maritime & Ocean Engineering Research Institute). The inclined shaft of the propeller creates strong cavitation, which occurs around the root of the propeller blade. This cavitation creates impacts through the collapsing process that are very severe, and are useful for realistic and efficient cavitation erosion tests. In the present study, the newly developed cavitation erosion test method is successfully employed to evaluate marine coatings that is mainly composed of epoxy elastomer or silicone polymer material. Silicone polymer-type paint B was found to have three times larger endurance than epoxy elastomer-type paint A.     

An experimental study on an auxiliary towing system for an FPSO using active thrusters

It is ideal to design the best hull shape for a floating production storage and offloading unit (FPSO) that meets all performance criteria from an engineering point of view. However, in reality, it is difficult to satisfy all the criteria at the same time. If one of the performances cannot meet the criteria, then additional equipment or systems are installed to improve that performance. In this paper, when an FPSO cannot meet the towing stability inherently, we attempt to establish a procedure for determining an auxiliary towing system. Firstly, various systems that can be applied to the FPSO are compared and reviewed to improve the towing stability of the FPSO. Among them, using three active thrusters was chosen as the auxiliary towing system. Improvement of towing stability was verified from a towing model test conducted at the Maritime Research Institute Netherlands (MARIN). However, thruster cavitation was raised as a key problem when using thrusters for a purpose for which they were not intended. A thruster cavitation model test was additionally performed to check the safety of the thrusters. Based on these results, a safe operating range under extreme condition was confirmed by observing the occurrence of thruster cavitation. The predicted maximum unit total thrust of each thruster was compared with the observed safe operating range. Finally, the effectiveness and safety of the auxiliary towing system was verified.     

SCA6—1型声学水位计可靠性设计与预计

本文就ＳＣＡ６－１型声学水位计的可靠性设计与预测做了研究和计算,得出了可靠性指标和可靠性保障技术。这是对产品质量要求必不可少的。本文所使用的方法可为其它产品所借鉴     

A combined wind and wave energy-converter concept in survival mode: Numerical and experimental study in regular waves with a focus on water entry and exit

A combined wind and wave energy converter concept, named STC concept was proposed. Model tests were performed in terms of operational and survival modes. Water entry and exit phenomena as well as green water on deck were observed during the survivability model tests. In this paper, a nonlinear numerical model based on a blended station-keeping potential-flow solver with a local impact solution for bottom slamming events and an approximated model for the water shipped on the deck is proposed to simulate these nonlinear phenomena. Physical investigation of the water entry and exit process was firstly carried out and uncertainty analysis of the model test results were performed. Numerical comparisons between the nonlinear solver and model test results are then performed in terms of mean, wave frequency and double wave frequency motion response components. The slamming and green water involved in the water entry process are specially investigated, in terms of the physical evolution and the effects on the dynamic motion responses. The validation work on the occurrence of slamming and water on deck as well as the slamming pressure are performed.     

Experimental and theoretical study of a cylindrical oscillating water column device with a quadratic power take-off model

The wave power extraction by a cylindrical oscillating water column (OWC) device with a quadratic power take-off (PTO) model was studied experimentally and theoretically. In the experiment, a scaled model OWC was tested in a wave flume, with an orifice being used to simulate a quadratic PTO mechanism. In the theoretical analysis, the quadratic PTO model was linearized based on Lorenz's principle of equivalent work, which allows us to perform a frequency domain analysis using an eigen-function matching method. The effects of higher harmonic components and the spatial non-uniformity of the surface velocity inside the chamber were discussed. A semi-analytical model was proposed to understand the viscous loss affecting the measured capture length. Our treatment of the quadratic PTO model was validated by comparing quasi-linear theoretical capture length and the laboratory measurement. Our results also showed that the effects of spatial non-uniformity and viscous loss could be noticeable for shorter waves.     

深海采矿循环式水力集矿系统设计与数值研究

为使深海采矿作业更为高效、环保,提出了一种用于深海采矿的循环式水力集矿系统设计方案。该系统主要由集矿头、矿-沙分离器、水-沙分离器、水泵以及连接各部件的管道组成。采用基于欧拉法的液固两相流计算模型对该系统的关键问题,即矿-沙分离器和水-沙分离器的泥沙颗粒流动进行数值研究。相间拖曳力采用Richardson-Zaki模型。液相与固相湍流分别采用标准k-ε模型和Tchen湍流响应模型。该模型经验证对于直径0.165 mm与0.27 mm细颗粒具有较高精度。利用该模型,以0.165 mm泥沙颗粒为例,得到了两种分离器的分离效果与入口流速之间的规律,分析了两者颗粒浓度分布与流场特征。结果表明,两种分离器的性能均与入口流速有关,在选取适当入口条件时均可取得良好效果。     

靶场测量装备中GPS换装北斗卫星导航系统方案设计

目前,根据装备试验要求,利用北斗卫星导航系统全面替换靶场测量装备中所使用的GPS已成为必须开展的工作。如果直接替换,则现有测量系统需重新进行测试,代价较高。为此,结合靶场测量装备实际情况,设计一种基于北斗卫星导航系统,集定位、测姿、授时为一体的便携式信息采集分发系统,系统具备多种对外数据传输接口,无需对现有装备进行较大改造,即可全面实现北斗取代GPS的目的。     

Development of wavelet network model for accurate water levels prediction with meteorological effects

Accurate water levels modeling and prediction is essential for safety of coastal navigation and other maritime applications. Water levels modeling and prediction is traditionally developed using the least-squares-based harmonic analysis method that estimates the harmonic constituents from the measured water levels. If long water level measurements are not obtained from the tide gauge, accurate water levels prediction cannot be estimated. To overcome the above limitations, the current state-of-the-art artificial neural network has recently been developed for water levels prediction from short water level measurements. However, a highly nonlinear and efficient wavelet network model is proposed and developed in this paper for water levels modeling and prediction using short water level measurements. Water level measurements (about one month and a week) from six different tide gauges are employed to develop the proposed model and investigate the atmospheric changes effect. It is shown that the majority of error values, the differences between water level measurements and the modeled and predicted values, fall within the −5 cm and +5 cm range and root-mean-squared (RMS) errors fall within 1–6 cm range. A comparison between the developed highly nonlinear wavelet network model and the harmonic analysis method and the artificial neural networks shows that the RMS of the developed wavelet network model when compared with the RMS of the harmonic analysis method is reduced by about 70% and when compared with the RMS of the artificial neural networks is reduced by about 22%. It is also worth noting that if the atmospheric changes effect (meteorological effect) of the air pressure, the air temperature, the relative humidity, wind speed and wind direction are considered, the performance accuracy of the developed wavelet network model is improved by about 20% (based on the estimated RMS values).     

Coupled study of water-stable isotopes and anions in porewater for characterizing aqueous transport through the Mesozoic sedimentary series in the eastern Paris Basin

This study presents data on chloride and bromide concentrations in porewater, water and anion diffusion coefficients, and their accessible porosities based on radial diffusion experiments on rock samples collected from a 2000 m-deep borehole (EST433) drilled by Andra in the eastern Paris Basin. The distributions of water stable isotope and chloride concentrations in porewater along this column reveal transient flows of water and solutes between the aquitard layers and the surrounding aquifers. These distributions confirm the occurrence of two separate aquitard/aquifer systems: “Oxfordian/Callovo–Oxfordian/Dogger” and “Dogger/Liassic/Rhaetian”. This separation is confirmed by Cl⁻/Br⁻ ratios, which are low in Liassic and Dogger porewater, suggesting the influence of primary brines, and which are close to the marine ratio in the Dogger groundwater. Based on these results, transport simulations in the two systems were carried out according to different scenarios. The simulation results confirm that transport properties obtained in the laboratory at sample scale may be extrapolated to the formation scale. It is highly probable that diffusion is the main transport process in the Callovo–Oxfordian formation. This may also be the case in the Dogger/Liassic layer, although a limited contribution from advection cannot be totally excluded. By testing different scenarios of boundary conditions in diffusive models, it is proposed that the Dogger aquifer was first activated in the Early Miocene.     

A two-dimensional analytical model of vertical water entry for asymmetric bodies with flow separation

The vertical water entry of asymmetric two-dimensional bodies with flow separation is considered. As long as there is no flow separation, linearised Wagner's theory combined with the modified Logvinovich model has been shown to provide computationally fast and reliable estimates of slamming loads during water entry. Tassin et al. [11] introduced the fictitious body continuation (FBC) concept as a way to extend the use of Wagner's model to separated flow configurations, but they only considered symmetric bodies. In the present study, we investigate the ability of the FBC concept to provide accurate estimates of slamming loads for asymmetric bodies. In this case, flow separation may not occur simultaneously on both sides of the body. During an intermediate phase, slamming loads are governed by a competition between the local drop in pressure due to partial flow separation and the ongoing expansion of the wetted area. As a first benchmark for the model, we consider the water entry of an inclined flat plate and compare the FBC estimates with the results of a nonlinear model. Then, we consider the case of a foil and compare the FBC results with computational fluid dynamics predictions. In both cases, we find that the FBC model is able to provide reliable estimates of the slamming loads.     

CTD电控多瓶采水器中电磁式释放机构设计与试验

文章概述了用电磁方式控制采水器释放机构的可行性，介绍了释放机构的工作原理、结构和特点，给出了应用实例试验中的测量方法和结果。     

Design of a hydraulic power take-off system for the wave energy device with an inverse pendulum

This paper describes a dual-stroke acting hydraulic power take-off （PTO） system employed in the wave energy converter （WEC） with an inverse pendulum. The hydraulic PTO converts slow irregular reciprocating wave motions to relatively smooth, fast rotation of an electrical generator. The design of the hydraulic PTO system and its control are critical to maximize the generated power. A time domain simulation study and the laboratory experiment of the full-scale beach test are presented. The results of the simulation and laboratory experiments including their comparison at full-scale are also presented, which have validated the rationality of the design and the reliability of some key components of the prototype of the WEC with an inverse pendulum with the dual-stroke acting hydraulic PTO system.     

快速开发背景下海岛的生态安全评价——以平潭岛为例

随着人类活动的加剧与社会经济的持续发展,对海岛的开发日益剧烈.动态评价海岛开发建设过程中的生态安全状况是提出生态环境保护对策的前提;深入分析影响海岛生态安全的主要影响因子是准确调整海岛发展政策的客观依据,对缓解海岛开发建设与生态安全的矛盾,实现海岛建设与生态环境相互协调具有重要意义.本研究依据平潭岛的实际情况筛选出34个评价因子构建生态安全评价指标体系,指标涵盖社会、经济、环境3个方面.采用熵权法计算各评价指标权重提高了评价的客观性与准确性,通过主成分投影法对平潭岛2005—2015年的生态安全状况进行动态评价,探讨了平潭岛生态安全的变化状况.其中生态安全状况最差与最好的年份分别为2006、2011年,2006年的生态安全投影值最小,只有0. 004 1; 2011年的生态安全投影值最高,为0. 178 1.绘制生态安全状况趋势图发现2009—2011年生态安全投影值的变化最为明显.通过灰色关联法进行驱动力分析发现社会消费品零售总额增长率、财政总支出、固定资产投资额增长率、工业总值增长率、接待旅游人数、城镇人口失业率、水产品总产量、生活垃圾无害化处理率、耕地年均损失率等9个社会经济指标对平潭岛的生态安全状况起到关键影响.     

正弦干扰下时滞系统的状态预测观测器与前馈-反馈预测控制器设计

研究控制变量含有时滞的线性系统在外部正弦干扰下的最优减振预测控制问题。利用系统的控制向量和被控对象的预测输出向量 ,设计了 1种全维状态预测观测器。并将该状态观测器用于时滞控制系统的最优前馈 -反馈预测控制中。频域分析表明 ,应用该状态预测观测器可将闭环系统的时滞项移至系统闭环结构之外 ,从而其优化控制规律完全可以按无时滞系统进行设计。时域分析表明 ,设计的预测控制器对外部正弦干扰有较强的鲁棒性 ,得到的结果关于二次型平均性能指标是次优的     

Use of voltammetric solid-state (micro)electrodes for studying biogeochemical processes: Laboratory measurements to real time measurements with an in situ electrochemical analyzer (ISEA)

Solid-state voltammetric (micro)electrodes have been used in a variety of environments to study biogeochemical processes. Here we show the wealth of information that has been obtained in the study of sediments, microbial mats, cultures and the water column including hydrothermal vents. Voltammetric analyzers have been developed to function with operator guidance and in unattended mode for temporal studies with an in situ electrochemical analyzer (ISEA). The electrodes can detect the presence (or absence) of a host of redox species and trace metals simultaneously. The multi-species capacity of the voltammetric electrode can be used to examine complex heterogeneous environments such as the root zone of salt marsh sediments. The data obtained with these systems clearly show that O₂ and Mn²⁺ profiles in marine sedimentary porewaters and in microbial biofilms on metal surfaces rarely overlap indicating that O₂ is not a direct oxidant for Mn²⁺. This lack of overlap was suggested originally by Joris Gieskes' group. In waters emanating from hydrothermal vents, Fe²⁺, H₂S and soluble molecular FeS clusters (FeS_aq) are detected indicating that the reactants for the pyrite formation reaction are H₂S and soluble molecular FeS clusters. Using the ISEA with electrodes at fixed positions, data collected continuously over three days near a Riftia pachyptila tubeworm field generally show that O₂ and H₂S anti-correlate and that H₂S and temperature generally correlate. Unlike sedimentary environments, the data clearly show that Riftia live in areas where both O₂ and H₂S co-exist so that its endosymbiont bacteria can perform chemosynthesis. However, physical mixing of diffuse flow vent waters with oceanic bottom waters above or to the side of the tubeworm field can dampen these correlations or even reverse them. Voltammetry is a powerful technique because it provides chemical speciation data (e.g.; oxidation state and different elemental compounds/ions) as well as quantitative data. Because (micro)organisms occupy environmental niches due to the system's chemistry, it is necessary to know chemical speciation. Voltammetric methods allow us to study how chemistry drives biology and how biology can affect chemistry for its own benefit.