A hybrid analytical model of sterilization effect on marine bacteria using microbubbles interacting with shock wave

The present paper reports on a hybrid analytical model consisting of a biological probability model and a physical impact model proposed to predict the cell viability ratio of a sterilization method for marine bacteria using microbubbles interacting with a shock wave. The physical impact model of interaction between a microbubble and a shock wave is developed on the basis of the bubble motion analysis with experimental pressure data and a one-dimensional numerical simulation. An underwater shock wave produced by microbubble motion is simulated using a second-order finite differential scheme by means of bubble surface velocity variation obtained from Herring’s bubble motion equation, and the radius of the sterilized space around a microbubble is estimated by the critical pressure that just causes cell wall damage of marine bacteria. The sterilization effect predicted by the present hybrid analysis shows a good agreement with the bio-experimental result.     

Cruise ship market segmentation: a 'non-traditional' port case study

Market segmentation in the cruise ship industry is an essential tool for securing a favourable market share. A case study of a mid-sized vessel operating from a 'non-traditional' port provides insights of the demographic and socio-economic characteristics of a cruise population. The questionnaire also supports the logic for a strong local/regional marketing effort and validates the rationale for the provision of a cruise service from a 'non-traditional' port.     

基于模糊控制与遗传算法的潜艇自动舵设计与实现

在潜艇六自由度模型的基础上,根据一阶二阶波浪力对于航行在近水面潜艇深度的影响,采用模糊控制技术和遗传算法设计了基于二级模糊控制的遗传算法调整控制参数的潜艇自动舵控制系统.通过在近水面和水下两种状态对控制器性能仿真与结果分析,说明该自动舵具有很好的控制效果,响应较快,静差较小,具有较强抗干扰能力,对于近水面的深度控制有稳定的控制作用.     

Optimal handling capacity at a berth

In a recent paper Wanhill [1] described a method for determining the number of berths that should be provided at a port so that the total usage cost would be minimized. However, in many situations a port will provide a single specialized berth to cater for a particular type of cargo; for example, the unloading of iron-ore at a steelworks or the discharge of oil at a general cargo port. The problem then is not one of deciding on the number of berths to be built but rather that of finding the optimal cargo handling capacity for the single berth available. A model is presented in this paper indicating how such a decision may be made, and two examples give approximate lower and upper bounds for the optimal capacity for many practical cases. A second paper will show how a theoretical model often has to be modified in the light of particular circumstances.     

The influence of the Agulhas Current on the adjacent coastal ocean: possible impacts of climate change

The dynamics of the coastal ocean along the southeastern coast of Africa is dominated by a strong and intense western boundary current, the Agulhas Current. With a near-uniform, narrow continental shelf and a steep shelf slope that stabilizes this current, the trajectory of the Agulhas exhibits great stability. The only substantial perturbation occurs with the irregular passage of a Natal Pulse, a soliton meander. The initiation of this meander at the Natal Bight is due to a barotropic instability when the intensity of the landward border of the current exceeds a certain threshold value. This may come about with natural fluctuations in the current or with the adsorption of deep-sea eddies onto the current. Under a climate change scenario of altered wind stress curl over the South Indian Ocean it is conceivable that the threshold for the triggering of a Natal Pulse will occur more frequently. This will lead to a situation where the current axis on average lies further offshore. The possible consequences of such a situation on the rainfall of the coast, on the ecology of estuaries and the coastal ocean, and on the socio-economics of the region is discussed.     

Locomotion by mechanical pectoral fins

The objectives of this study were the development of a new device for maneuvering an underwater vehicle using the mechanism of a fish swimming, an experimental and theoretical analysis of the hydrodynamic characteristics of the device, and its application to maneuvering a fish robot. Observations and experimental analysis of the pectoral fins of a black bass (Micropterus salmoides) revealed that the locomotion of the fish, such as swimming forward at low speed, swimming backward, and turning in a horizontal plane is generated by using a combination of a feathering motion and a lead-lag motion of the pectoral fins. A mechanical pectoral fin making a feathering motion and a lead-lag motion generates a thrust force in a range of phase differences between both motions. The unsteady vortex lattice method, including the effect of viscosity, can express fairly well the unsteady forces acting on the mechanical pectoral fin in the range of phase differences where it exerts the thrust force. The fish robot, consisting of a model fish body and a pair of mechanical pectoral fins, can not only swim forward and turn in almost the same position, but can also swim in a lateral direction without changing the yaw angle. Translation of an article that appeared in the Journal of The Society of Naval Architects of Japan, vol. 182 (1997): The original article won the SNAJ prize, which is awarded annually to the best papers selected from the SNAJ Journal, JMST, or other quality journals in the field of naval architecture and ocean engineering.     

Vibration-assisted decommissioning of a slip joint: Application to an offshore wind turbine

An alternative option to the traditional grouted joint for wind turbines is a direct steel-to-steel connection, also known as slip joint. In a recently published work, a proof of concept of a vibration-assisted installation and decommissioning technique of a slip joint was illustrated. Leveraging on the obtained results, the current study shows for the first time a decommissioning campaign carried out using a vibration-assisted technique applied on a prototype hydraulic wind turbine tower located in the North Sea, and connected to the monopile through a slip joint. The key aspect of the dismounting procedure is a priori knowledge of the resonance frequency clusters corresponding to the slip joint’s cross-sectional modes. Therefore, field hammer tests and experimental modal analysis were carried out inside the wind turbine tower. The identified frequencies and mode shapes were then compared with numerical ones estimated by a finite element model of the investigated structure. The comparison showed that a set of frequency clusters can be directly selected from a detailed numerical model. The preparatory work of the slip joint decommissioning was then executed by installing electric shaker devices, based on the dynamic identification results, and hydraulic jacks mounted inside the wind turbine tower. A first decommissioning trial was carried out in May 2019, while the final decommissioning was performed in August 2019. After analysing the measurements of the hydraulic pressures, displacements and excitation frequencies during the decommissioning campaigns, the results showed that it is possible to disconnect the slip joint if, in combination to a vertical static force, one of the identified cross-sectional mode shapes is excited. The vibration-assisted decommissioning proved to be a successful technique to dismount the connection in a controlled and straightforward manner.     

Resistance and seakeeping numerical performance analyses of a semi-small waterplane area twin hull at medium to high speeds

The hydrodynamic analysis of a new semi-small waterplane area twin hull (SWATH) suitable for various applications such as small and medium size passenger ferries is presented. This may be an attractive crossover configuration resulting from the merging of two classical shapes: a conventional SWATH and a fast catamaran. The final hull design exhibits a wedge-like waterline shape with the maximum beam at the stern; the hull ends with a very narrow entrance angle, has a prominent bulbous bow typical of SWATH vessels, and features full stern to arrange waterjet propellers. Our analysis aims to perform a preliminary assessment of the hydrodynamic performance of a hull with such a complex shape both in terms of resistance of the hull in calm water and seakeeping capability in regular head waves and compare the performance with that of a conventional SWATH. The analysis is performed using a boundary element method that was preliminarily validated on a conventional SWATH vessel.     

新型小水线面双体船阻力和耐波性数值模拟分析（英文）

The hydrodynamic analysis of a new semi-small waterplane area twin hull(SWATH) suitable for various applications such as small and medium size passenger ferries is presented. This may be an attractive crossover configuration resulting from the merging of two classical shapes: a conventional SWATH and a fast catamaran. The final hull design exhibits a wedge-like waterline shape with the maximum beam at the stern; the hull ends with a very narrow entrance angle, has a prominent bulbous bow typical of SWATH vessels, and features full stern to arrange waterjet propellers. Our analysis aims to perform a preliminary assessment of the hydrodynamic performance of a hull with such a complex shape both in terms of resistance of the hull in calm water and seakeeping capability in regular head waves and compare the performance with that of a conventional SWATH. The analysis is performed using a boundary element method that was preliminarily validated on a conventional SWATH vessel.     

船舶在狭水道中运用GPS、ARPA、ECDIS定位技术研究

船舶在狭水道或进出港航道航行时,为确保船舶航行在预定的航迹线上,传统的定位与导航方法大多是利用助航标志。本文基于GPS、船用雷达(ARPA)和电子海图(ECDIS)等航海仪器与设备功能特点,就船舶运用GPS、船用雷达和电子海图以确定船舶在狭水道航行的航迹线方法作了研究,并就方法的运用提出了相应的注意事项。     

Optimal reefer slot conversion for container freight transportation

Given a fleet of container ships of varying capacity, a cost-efficient approach for improving fleet utilization and reducing the number of delayed containers is to optimize the sequence of container ships in a given string, a problem which belongs to the large ship-deployment class. A string sequence with ‘uniformly’ distributed ship capacity is more likely to accommodate a random container shipment demand. The number of one’s total ship slots acts as a gauge of the capacity of the container ships. Meanwhile, there are two types of ship slots: dry slots and reefer slots. A dry slot only accommodates a dry container, while a reefer slot can accommodate either a dry or a reefer container. The numbers of dry and reefer slots for ships in a string are different. Therefore, in this study, we propose a model that considers both dry and reefer slots and use it to elucidate the optimal ship-deployment sequence. The objective is to minimize the delay of dry and reefer containers when the demand is uncertain. Furthermore, based on the optimal sequence deduced, the study also investigates the need to convert some dry slots to reefer slots for the container ships.     

复杂结构的舰船电力系统仿真算法研究

针对复杂结构的舰船电力系统的特点提出了一种新的仿真方法,该方法分为两部分:稳态计算和动态计算.稳态计算部分采用基于网络的节点电势法,充分考虑了线路压降对异步电动机参数的影响;动态计算部分将稳态计算的结果作为仿真初始值,采用变步长节点分析法求解微分方程.仿真和试验结果表明,该算法适用于辐射形、环形和网状形等任何复杂结构的舰船电力网络,方法简单、精度高、收敛性好,易于计算机实现.     

Comparison of the crashworthiness of various bottom and side structures

The purpose of this work is to compare the resistance with damage of various types of double bottom structures in a stranding event. The comparative analyses are made by use of a commercial, explicit finite element program. The ship bottom is loaded with a conical indenter with a rounded tip, which is forced laterally into the structures in different positions. The aim is to compare resistance forces, energy absorption and penetration with fracture for four different structures. Those four structures are: a conventional double bottom, a structure (presently protected through a patent) with hat-profiles stiffened bottom plating, a structure where all-steel sandwich panel is used as outer shell and a bottom structure stiffened exclusively with hat-profiles. The paper shows that it is indeed possible to elevate the crashworthiness of side and bottom structures with regards to the loading considered here without increasing the structural weight.     

影响船舶弃船时机决策的各环境因素分析

当船舶发生海难事故后,船舶弃船时机的正确决策关系到船舶安全尤其是海上人命安全,本文分析了影响该决策行为的各种环境因素,对弃船时机的正确选择做一个初步分析,为进一步研究奠定一些基础。     

A risk assessment model with systematical uncertainty treatment for container shipping operations

ABSTRACT

The substantial adverse effects of risk factors on container shipping and logistics promoted a deep integration of risk analysis into the decision-making process. This paper aims to develop a well-grounded quantitative model to operational risk in a container shipping context. Considering uncertainty as a primary component of the risk concept, methods were employed in an inter-complementary manner to enable not only a sense of foreseeability but also a deeper look into the weaknesses of the knowledge base. The intersubjectivity of the input extraction process was supported by the Evidential Reasoning (ER) algorithm. Risks are then assessed based on a Fuzzy Rules Bayesian Network (FRBN) model with a 2-level parameter structure before meaningful interpretations can be derived through a new risk mapping approach. Besides an illustrative case study, the model was tested by sensitivity analysis and an examination of multiple validity claims.     

一种新型舵机装置的研究

本文提出一种利用滚动螺旋将液压缸的直线运动直接转换成舵叶转动的机构,这种机构的优点是推舵装置和动力传动装置均布置在上舵杆内,最大限度地节省了空间.本文对执行机构的传动原理、结构进行了介绍,并对设计计算中的薄弱环节--滚珠与滚道的高副接触进行了详尽的分析.     

船舶柴油机注汽涡轮增压系统

为了改善涡轮增压柴油机在低工况运行时,会出现增压压力不足、燃烧过量空气系数小和废气排温较高等固有特性,提出了一种利用增压器废气余热产生水蒸汽,并注入涡轮来提高增压器的压比和空气量的新方法。这种新方法可以改善涡轮增压器与柴油机的匹配,从而可提高柴油机的性能。试验结果证实了该方法的有效性。     

Evaluation of added resistance in regular incident waves by computational fluid dynamics motion simulation using an overlapping grid system

A computational fluid dynamics simulation method called WISDAM-X was developed to evaluate the added resistance of ships in waves. The Reynolds-averaged Navier–Stokes (RANS) equation was solved by the finite-volume method and a MAC-type solution algorithm. An overlapping grid system was employed to implement rigorous wave generation, the interactions of ships with incident waves, and the resultant ship motions. The motion of the ship is simultaneously solved by combining the solution of the motion of the ship with the solution of the flow about the ship. The free surface is captured by treatment by the density-function method. The accuracy of WISDAM-X is examined by a comparison with experimental data from a container carrier hull form, and shows a fairly good agreement with respect to ship motion and added resistance. Simulations were also conducted for a bow-form series of a medium-speed tanker to examine the effectiveness of the WISDAM-X method as a design tool for a hull form with a smaller resistance in waves. It was confirmed that the WISDAM-X method can evaluate the added resistance with sufficient relative accuracy and can be used as a design tool for ships.     

利用环境振动分析对受超大型船舶撞击后的码头进行结构监测的快速工具（英文）

Operational modal analysis is a non-destructive structural investigation that considers only the loads resulting from service conditions.This approach allows the measurement of vibrations on a given structure with no need to interrupt its use.The present work aims to develop a numerical model to represent the global structural behavior of a vessel breasting dolphin using a technique that is simple and cheap in order to obtain a fast answer about the stiffness of a pier after the collision of ships with capacity up to 400,000 t.To determine the modes of vibration,one accelerometer was installed on the breasting dolphin located on the pier and a frequency domain technic was conducted over recorded data to obtain modal parameters of the structure.In situ measurements were compared to data from a finite element model based on the original structural design in order to adapt the model to accurately represent the actual behavior of the system.This allowed a reliable structural analysis that accounted for existing structural damage and imperfections.The results of the experiment presented herein are the numerical characterization of the structure,along with the structural analysis to assess the degree of damage currently observed on the system.It is noted that the dolphin subjected to ship impacts presents a reduction in stiffness of approximately10% and its global damage level can be monitored from now after new accidents.     

波浪和海流对浮式海洋牧场的作用（英文）

The paper is partly a review on hydrodynamic and structural aspects of fish farms. In addition, new numerical results are presented on the stochastic behavior of bending stresses in the floater of a realistic net cage in extreme wave conditions. The behavior of traditional-type fish farms with net cages and closed fish farms in waves and currents is discussed. Hydroelasticity can play a significant role for net cages and closed membrane-type fish farms. The many meshes in a net cage make CFD and complete structural modeling impracticable. As an example, a hydrodynamic screen model and structural truss elements are instead used to represent the hydrodynamic loading and the structural deformation of the net. In addition, the wake inside the net due to current plays an important role. The described simplified numerical method has been validated by comparing with model tests of mooring loads on a single net cage with two circular elastic floaters and bottom weight ring in waves and currents. It is discussed which parts of the complete system play the most important roles in accurately determining the mooring loads. Many realizations of a sea state are needed to obtain reliable estimates of extreme values in a stochastic sea. In reality, many net cages operate in close vicinity, which raises questions about spatial variations of the current and wave environment as well as hydrodynamic interaction between the net cages. Live fish touching the netting can have a non-negligible influence on the mooring loads. It is demonstrated by numerical calculations in waves and currents that a well boat at a net cage can have a significant influence on the mooring loads and the bending stresses in the floater. The latter results provide a rational way to obtain operational limits for a well boat at a fish farm. Sloshing has to be accounted for in describing the behavior of a closed fish farm when important wave frequencies are in the vicinity of natural sloshing frequencies. The structural flexibility has to be considered in determining the natural sloshing frequencies for a membrane-type closed fish farm. Free-surface non-linearities can matter for sloshing and can, for instance,result in swirling in a certain frequency domain for a closed cage with a vertical symmetry axis.