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In this study, through experimental research and an investigation on large datasets of the durability parameters in ocean engineering, the values, ranges, and types of distribution of the durability parameters employed for the durability design in ocean engineering in northern China were confirmed. Based on a modified theoretical model of chloride diffusion and the reliability theory, the service lives of concrete structures exposed to the splash, tidal, and underwater zones were calculated. Mixed concrete proportions meeting the requirement of a service life of 100 or 120 years were designed, and a cover thickness requirement was proposed. In addition, the effects of the different time-varying relationships of the boundary condition (Cs) and diffusion coefficient (Df) on the service life were compared; the results showed that the time-varying relationships used in this study (i.e., Cs continuously increased and then remained stable, and Df continuously decreased and then remained stable) were beneficial for the durability design of concrete structures in marine environment.

Motivated by the requirement for developing a lightweight and nimble underwater vehicle-manipulator system (UVMS), this paper presents a novel design of the overall framework and the functional modules for a flippers-driven UVMS (F-UVMS), which is equipped with 6 biomimetic flipper propulsors to produce thrust. With taking into account the material properties and flexible deformation, the dynamic model of the flexible flipper is derived. The fluid-solid coupling analysis reveals the wake vorticity characteristics and the mechanism of the flexible flipper. Besides, by introducing the dimensionless swimming number Sw, the force-parameter relationship of the flexible flipper is revealed. By comparing the hydrodynamic characteristics of the flexible flipper and rigid flipper, it can be concluded that the flexible flipper has higher propulsion efficiency. The motion patterns of the F-UVMS are designed by proposed coordinated control strategy. Moreover, through computational fluid dynamics method, the hydrodynamic effects of the biomimetic flipper propulsors during forward motion are analyzed. Finally, the force measurement experiments and the thrust efficiency experiments validate the practicability of the proposed biomimetic flipper propulsor. The motion feasibility of the F-UVMS is verified by the motion experiments.

Robots have the potential to assist and complement humans in the exploration of hostile environments. For example, underwater vehicle-manipulator systems (UVMSs) have been researched and applied in underwater operations. Motivated by the need for collecting marine organisms cultivated in shallow sea aquafarm, a light-weight and portable UVMS propelled by flexible flippers (named, F-UVMS), rather than typical propellers or jet-based propulsion systems, is investigated. To this end, integrative mechatronic design of F-UVMS is first presented, involving 6 flipper propulsors for generating thrust in a flapping way, a four-degree-of-freedom (4-DOF) arm for grasping, and a certain amount of onboard sensors for environment perception. A thrust-power measurement platform was established to evaluate thrust-power relationship for different sizes and stiffness of flippers. Meanwhile, the locomotion modalities of F-UVMS were analyzed. A framework based on nonlinear model predictive control (NMPC) method was implemented to govern autonomous tracking marine organisms. The capabilities of F-UVMS were validated through a series of experiments in laboratory pool and field missions in real sea conditions.

The aim of this paper to study the effect of power on the drilling of soda lima glass (SLG) using under water laser drilling technique. A 1.15 mm thickness SLG sheets were immersed 1mm below the water surface, then irradiated with CW CO2 laser. The laser parameters used were (24, 25 and 26) W power, (5, 7.5 and 10) sec and exposure time and (1, 2and 3) pulses. Were determined using images for samples and study quality of holes using images. These ones of the dimensional of hole and crack length measured by image j program of the samples, it was watched that hole diameter and the length of cracks could be regulated by the power, time and no. of pulses. When power or pulses were increased, the hole diameter increased. The length of cracks decreased with increased no. of pulses and increased when the power increased. The small hole was 0.469mm found at working power (24) W, five seconds and one pulse for hole diameter. While, the minimum crack length was 0.4mm found at three pulse, five sec. and 24 W power. In addition, the parameters were analyzed statistically using design of expert software, Box Behnken design from surface response methodology and the results were significant.

Biomimetic underwater robots have attracted considerable research attention globally, owing to their quieter actuations, higher propulsion efficiency, and stronger maneuverability when compared with conventional underwater vehicles equipped with axial propellers. This article provides a comprehensive survey of current research in this field. First, we review the development status of biomimetic underwater robots in both body/caudal fin (BCF), median/paired fin (MPF), and their hybrid propulsion modes. Then, we outline the motion control methods employed in biomimetic underwater robots, including open-loop swimming control and typical closed-loop control strategies. In particular, we detail our latest studies on the RobCutt series underwater robots. On this basis, some critical issues and future directions are summarized. We predict that biomimetic underwater robots will have excellent prospects in underwater environment exploration and resource utilization.

All underwater drilling and blasting operations generate seismic waves. However, due to a lack of suitable vibration sensing instruments, most studies on the propagation of seismic waves have been limited to shorelines near construction areas or wharfs, whereas comparatively few studies have been conducted on the larger seafloor itself. To address this gap, a seafloor vibration sensor system was developed and applied in this study that consists of an autonomous acquisition storage terminal, software platform, and hole-plugging device that was designed to record the blasting vibration intensities received through submarine rocks at a given measurement point. Additionally, dimensional analyses were used to derive a predictive equation for the strength of blast vibrations that considered the influence of the water depth. By combining reliable vibration data obtained using the sensor system in submarine rock and the developed predictive equation, it was determined that the water depth was an important factor influencing the measured vibration strength. The results using the newly derived equation were compared to those determined using the Sadowski equation, which is commonly used on land, and it was found that predictions using the derived equation were closer to the experimental values with an average error of less than 10%, representing a significant improvement. Based on these results, the developed sensor system and preliminary theoretical basis was deemed suitable for studying the propagation behavior of submarine seismic waves generated by underwater drilling and blasting operations.

In recent years, water disasters have increased in Japan. In water disaster, remote controlled vehicles which work for disaster recovery must run in water environment. Since underwater ground is likely to be soft, the vehicle has a risk of stuck. If a vehicle gets stuck at disaster sites, rescue work is difficult because it is not easily to access to that area. We must make a method for judging whether to run or not. For this purpose, we must quantitatively clarify the relationship between the trafficability and the strength, bearing capacity, etc. of underwater ground. We measured the cone index of underwater ground. From results, we confirmed that fragile layer was formed on the surface layer in underwater ground. We measured drawbar pull of a tracked carrier in test field. As a result, maximum drawbar pull of underwater ground was lower than on the ground. After slip occurs, drawbar pull of underwater ground was smaller than ground significantly.

In order to simulate the characteristics of underwater shield tunnels, a new large-scale model test system with high water pressure and high stress loading capacity was developed. The loading control mode of the hydraulic system can perform uniform loading and gradient loading. Moreover, the vertical and horizontal hydraulic loading can reach 0·8 MPa and 1·6 MPa. The water pressure loading system has a maximum capacity of 0·5 MPa. Based on an actual project, a model test of an underwater shield tunnel lining under real soil and water pressure conditions was carried out. New segment joints of the model were developed during the model testing. The lateral pressure coefficient at rest of the model strata was slightly larger than 0·5, and close to that of the field strata. It was also found that the water pressure had a reducing effect on the soil pressure under large buried depth and high water pressure conditions. This system can mostly meet the requirements of underwater or underground engineering model tests.

Recently, cooperative autonomous underwater vehicles (AUVs) have been deployed in application areas such as surveillance and protection of maritime infrastructures for inspection and monitoring purposes. These cooperative methodologies require wireless transmission of data between the different AUVs operating in the underwater environment. Communication over ranges exceeding 100 m exclusively relies on underwater acoustic communication. However, the propagating acoustic waves suffer from several challenges due to the presence of path loss, multi-path propagation, the slow and variant propagation speed, background noise, and Doppler distortion. Since the power supply of the AUVs is limited, communication must be very energy efficient and energy constraints have to be known to be able to plan the mission of AUVs. Due to the difficulties of real experiments, the modeling and simulation of the energy consumption and underwater acoustic communication play an essential role in studying and developing these systems. We provide a modular simulation model for the energy consumption and acoustic underwater communication of AUVs implemented in the network simulator OMNeT++ using the INET framework. More specifically, we extend several INET modules in such a way as to reflect the characteristics of AUVs and underwater communication. We study and analyze the AUVs’ energy consumption and dependence of the message quality on different properties such as those mentioned above.

The beauty of the beach and underwater of Bangsring beach make this beach one of the leading destinations in Banyuwangi Regency. However, until today how to enjoy the beauty of the underwater can exclusively be done by diving or snorkeling, which is quite troublesome and exhausting, especially for tourists who want to enjoy and looking entertainment in a simpler way. So the concept of bottom-glass in this design is offered as a problem solving in this study, while the concept of flat plate and flat-bottom is carried out to efficiently time and cost of shipbuilding, because with this flat plate concept, there is no rolling and other material bending process. The design of the main dimensions is made based on owner requirements are obtained based on field study and literature studies, then the main parameters are obtained (LOA = 12 m, total B = 5.6 m, B each hull = 0.94 m, hull spacing = 3.72 m, T = 0.7 m, H = 1.85 m, Vs = 10 knots). To maximize the design, 4 ship models were designed with these primary parameters, based on the analysis of resistance using Maxsurf Resistance, model 4 with a maximum resistance of 4.3 kN was chosen which tend to be more effective compared with the designs of model 1, model 2, and model 3 which has a maximum resistance of 8 kN, 4.9 kN and 5.3 kN. The results of the stability analysis carried out in this design with the load case 100%, 80%, 60%, 40%, and 20%, has met all requirements for intact stability IMO MSC.36 (63) for HSC multihull Annex 7.

The creation of competitive deep-sea soil-mining machines and complexes allows the transition to the development of deep-water deposits of polymetallic nodules and metalliferous silts, the extraction of sand and sapropel from the bottom of the sea, thus providing parity access to the mineral and energy resources of the World Ocean. The purpose of the work is to create methods and technical means for determining the strength characteristics of bottom soils in the surface layer, aimed at reducing the time of creation and effective use of machines by ensuring that their parameters correspond to real operating conditions. Usually, the properties of deep-sea soil in its natural bedding (in situ) are determined from the data of photo- and geoacoustic sounding or from cores raised from the seabed to the surface, and the working loads of machines, the resistance of the soil to destruction and other mechanical characteristics are estimated on the basis of the data obtained by geological methods. New methods and devices for point and continuous sampling of the bottom, adequately applied both on the surface and under water, provide sufficient reliability of the information obtained for practical use. The objectives of the study are to substantiate the theory of gravity sensing of underwater soils and their cutting, to determine the deformation and strength properties of the surface layer of the seabed, resistance to mechanical destruction and the characteristics of the interaction of machine mechanisms with silty soil. The novelty of the research is to establish the features of the interaction of the working bodies and the undercarriage of earth-moving machines with underwater viscoplastic soils, depending on the parameters of the working process, strength properties of the soil, characteristics of dynamic loading and geophotoprofiling of underwater routes. The practical value lies in the substantiation of the operational loads of deep-water earth-moving machines; an assessment of the characteristics of bottom soils in natural bedding, as well as a comprehensive study of bottom massifs, which make it possible to reduce the number of sampling stations, the total labor intensity of voyage operations, to establish an operational bottom background and optimal routes of mining systems.

During the operation of oil and gas transportation pipeline, condensate forms on the inner wall of the pipeline can lead to reduced transportation efficiency and potential safety hazards. Pigging is a widely used technology to remove deposition in pipelines. From the studies, it is found that the effect of pigging largely depends on the structure of the pig. The jetting pig is a new type of pigging device designed to prevent the blocking in the pigging process, and its baffles play an important role in guiding the jet fluid. In this paper, the impact of the structure of the baffle plate on the downstream flow field of the jetting pig is simulated and analyzed. The surface of the baffle plate is changed by using the curve of the contraction section of the water tunnel. It is found that the baffle plate structure has a great influence on the flow field at the outlet of the jet pig: (1) The increase of buffle area leads to the increase of turbulent kinetic energy and the decrease of velocity; (2) The rise of edge angle lead to the regular change of turbulent kinetic energy; (3) Different curved surfaces make the change of turbulent kinetic energy and velocity. The results in this study are helpful for a better understanding of mechanism of jetting pig and improved design of mechanical structure for improved pigging performance.

Underwater remotely operated vehicle (ROV) is used to monitor the subsea-surface mooring and piping lines. In this study, the hydrodynamic characteristics of a remote-operated vehicle are analysed ...

A simple underwater noise model suitable for use with explosive severance of well conductors and piles during the decommissioning of oil and gas subsea structures is introduced and evaluated against data from five projects in the US. This study focuses on a novel model for the determination of sound exposure levels. The model has been developed to enable determination of impact areas for marine mammals and fish. Simulated received underwater sound exposure levels were significantly correlated with measurements for all scenarios. The maximum total error achieved between simulations and measurements was 2.6%, suggesting that predictions are accurate to within 3% of the average measurement. A low relative bias was observed in the simulations when compared to measured values, suggesting only a small systematic underestimate (≤0.5% of average measurement) for most severance operations and a small overestimate (0.14%) for open water blasts.

Многолетняя практика применения регламентных норм учета русловых процессов и механизма транспорта донных руслоформирующих наносов подтверждает надежность принятых расчетов для проектирования и строительства подводных переходов магистральных трубопроводов (ППМТ) через большинство средних и крупных рек России. Но для рек, «перегруженных» донными наносами, традиционные расчетные методики параметров подводной траншеи трубопровода с учетом заносимости оказываются недостаточными и требуют дополнительных решений. Данная проблема была выявлена при строительстве основной и резервной ниток ППМТ ВСТО-2 через реку Амур и обусловлена гидроморфологическими особенностями, спецификой водного режима и значительным расходом донных наносов, характерными для этого водного объекта. В настоящей статье представлена усовершенствованная технология разработки траншеи ППМТ путем создания так называемых ложных траншей на участках с максимальными удельными расходами донных наносов. На примере строительства ППМТ ВСТО-2 (резервная нитка через реку Амур) рассмотрены сложности проектирования и строительства трубопровода при значительных объемах транспорта донных наносов, проанализированы риски строительства в данных условиях, описаны планирование и реализация технического решения по созданию ложных траншей для перехвата донных наносов. The long-term practice of regulatory standards for recoding of river bed evolutions and the transport mechanism of bottom riverbed-building sediments proves reliability of the adopted calculations for design and construction of underwater crossings of main pipelines through majority of medium and large rivers of Russia. However, in respect of the rivers which are «overloaded» with bottom sediments, the conventional calculation methods of parameters of the underwater pipeline trench, considering sediment accumulation, are insufficient and require additional solutions. This problem was identified during construction of the underwater crossing of the ESPO-II pipeline system across the Amur River and is associated with hydromorphological features, specifics of the water regime and significant flow rate of bottom sediments typical for this water body. This article presents an improved technology for developing an underwater trench by establishment of so-called false trenches in the areas with maximum specific flowrate of bottom sediment. Based on the example of construction of the underwater crossing of the reserve pipeline leg, the difficulties related to design and construction of a pipeline with significant amount of bottom sediment transport are considered, risks of construction under these conditions are analyzed, planning and implementation of a technical solution for establishment of false trenches for intercepting bottom sediment are described.

This paper attempts to determine the law of motion of a tank as a large volumetric massive structure when immersed in a resisting liquid medium. The authors propose two methods for its determination. Dependence graphs of coordinates, speed, acceleration of the tank versus time are plotted. The dependence of time and speed of lowering of a massive storage structure on the volume of pumped water is determined. In addition, the range of the optimal volume of water pumped inside the tank for the purpose of its soft landing is determined.

_ The unsteady propeller forces of an underwater vehicle were numerically simulated using computational fluid dynamics to investigate the effects of the axial location of the stern planes. A benchmark study was undertaken using a three-bladed propeller; experimental results of the nominal inflow wake profile were analyzed and the unsteady propeller forces were measured. The numerical method was applied to predict the unsteady propeller forces in the SUBOFF model’s wake by varying the axial locations of the stern planes. Several remarks were made on the primary harmonics of the hull’s wakes and blade-rate propeller forces. Introduction The hydroacoustic noise, which matches multiples of the number of propeller blades and its rotational speed, known as “blade-rate (BR) noise,” has been increasingly used to manage hydroacoustics for naval vessels. BR noise can be caused by alternating blade loads owing to fluctuations in the angle of attack of the blades because marine propellers are operated in the nonuniform wake of ships’ hulls. The unsteady blade load produces unsteady propeller forces that are transmitted via the propeller shaft and bearing, thus producing undesirable vibration and noise. Although the resultant BR noise is a common issue for marine vessels, in particular, submarines and other underwater vehicles deployed for undersea defense systems and oceanographic survey systems require strict specifications for the acoustic signature. Therefore, the unsteady propeller forces must be improved for reduced detectability, because the vehicles should be able to operate without being discovered while sonar detection technology continues to improve.

The comparative analysis of the regulatory framework of the rules of the Russian river register (PRR) and the Russian maritime register of shipping (PMR) on the design and strength of ships on underwater wings (SEC) showed a significant difference between the methodologies of these rules. In this regard, a comparative analysis of the rules is possible only by performing numerical calculations for specific vessels. This paper presents the results of calculations for three SEC models. It is shown that with some extrapolation of the dependences given in the PRR, the values ​​of the calculated values ​​of bending moments for SEC, intended for operation on the excitement of h3%> 2.0 m, can be obtained from the PMR. For more weak wave modes Settlements. The existing approach to the pro-willer of the strength of the SEC wing devices should be recognized obsolete. It is necessary to either upgrade the PRR, taking into account modern advances in the field of hydrodynami, or allow the use of modern software complexes for computers based on numerical methods for solving hydrodynamic problems.

Autonomous underwater gliders (AUG) are a class of underwater vehicles that move using a buoyancy engine and forces from wings. Gliders execute turning motion with the help of a rudder or an internal roll control mechanism and the trajectory of the turn is a spiral. This paper analyses the sensitivity of the characteristics of spiral manoeuvre on the hydrodynamic coefficients of the glider. Based on the dynamics model of a gliding fish whose turn is enabled by a rudder, the effect of hydrodynamic coefficients of the hull and the rudder on the spiral motion are quantified. Local sensitivity analysis is undertaken using the indirect method. The order of importance of hydrodynamic coefficients is evaluated. It is observed that the spiral path parameters are most sensitive to the side force created by the rudder and the effect of the drag coefficient is predominant to that of the lift coefficients. This study will aid in quantifying the effect of change of geometry on the manoeuvrability of AUGs.

Introduction. The subject of the study is the process of diagnostics and repair of underwater crossings of the pipelines that transport natural and waste water, gas, oil and petroleum products. Comprehensive diagnostics helps to maintain the reliability of the pipeline system, reduces the cost of repair and restoration work, and also has a high environmental value. Optimization of the diagnostic procedure includes the selection of the most appropriate technical means and methods of inspection and the sequence of work for the location. No less important for organizations that maintain and operate underwater crossings are the issues of current and major repairs of such facilities: the choice of the most optimal engineering and technical solutions has a significant resource-saving effect. The purpose of this work is to present and describe the most effective methods and tools for diagnostics and repair of underwater pipelines to date. Materials and methods. In order to fully study the processes of diagnostics and repair of underwater crossings of the pipelines, a review of the relevant regulatory and technical documentation was conducted, scientific works of domestic and foreign scientists were analyzed, methodological developments and patents of organizations operating and servicing underwater crossings were considered. The review of the market of modern devices, devices and materials used for complex diagnostics and repair of underwater crossings of the pipelines was carried out. The main method of research is documentary. Results. Based on the survey, systematization and analysis of information on modern methods and advanced means of diagnostics and repair of underwater crossings of the pipelines were carried out. The types, methods and stages of diagnostics, devices and apparatuses for conducting surveys of underwater crossings, methods for detecting leaks, types, methods and stages of repairs, devices, apparatuses and materials used for carrying out repair and restoration work, methods of dismantling underwater crossings are considered. The limits of applicability of the considered methods and means of diagnostics and repair were outlined. Conclusions. The theoretical significance of the research consists in a complete description of the methods and means of diagnostics and repair of underwater crossings of the pipelines. The practical significance is the possibility of using the results of the research by specialists in the field of pipeline transport of natural and waste water, gas, oil and petroleum products.

Статья посвящена моделированию динамического равновесия установившегося движения протяженной кабельной линии с учетом действия гидродинамических сил сопротивления и неоднородной гидростатической силы. Учитывая различные условия и глубины укладки, а также требования функционального назначения и защиты от враждебных факторов морского дна, необходимо рассмотреть широкий диапазон кабелей с различными механическими характеристиками: трехжильный кабель с одиночным бронированием 2XS2YRAA, одножильный кабель с одиночным бронированием ZS-YJQ41 и одножильный кабель с двойным бронированием – аналог GASLMLTV. Целью работы является развитие цифровой технологии по моделированию укладки подводных коммуникационных и силовых кабелей, позволяющей учитывать многочисленные физико-механические явления, имеющие место при проведении реальных морских работ. Для достижения поставленной цели работы используется программная среда Matlab Math Works с использованием разработанного комплекса программ для инженерной оценки формы и натяжения провисающего участка кабеля. Научная новизна состоит в апробации модели подводной укладки кабеля, учитывающей действие неоднородной гидростатической силы. Результаты моделирования представлены в виде формы и натяжения провисающей части кабеля при различных углах схода кабеля с движущегося судна при различных механических параметрах кабелей. Практическое значение работы состоит в повышении эффективности освоения перспективных месторождений, путем определения характеристик укладки кабеля в условиях Арктического бассейна: газовое месторождение Лудловское, газоконденсатное месторождение Ленинградское, нефтяное месторождение Медынское-море. This article studies the numerical simulation of underwater steady motion of the cable line with account of hydrodynamic water resistance forces and non-uniform hydrostatic force. It is necessary to consider distinctive types of cables due to various depths, laying conditions, functional requirements and protection requirements against adverse factors of seabed. Three-core single armoured cable 2XS2YRAA, one-core single armoured cable ZS-YJQ41 and one-core double armoured cable – analogue GASLMLTV are considered in this article. The aim of the research consists in digital technology development for underwater cable laying modeling, which allows taking into account numerous physical and mechanical features. These features occur during real marine operations for communication and power cables. Programming and numeric computing platform Matlab Math Works with developed software package is chosen as the research method. Simulation results are presented in dimensionless form for cable shape and tension for engineering purposes. The novelty of the work consists in approbation of underwater cable laying analytical model considering non-uniform hydrostatic force. Simulation results are presented for underwater cable laying during reeling from spool mounted on the vessel, moving with constant speed for distinctive types of cables. The influence of the cable run-off angle on the investigated characteristics was also considered. The practical value of the research consists in increasing of efficiency of exploration of oil, gas and condensate fields by determining underwater cable laying characteristics for perspective fields. At the end of the paper, the results of estimation of the shape and tension of the cable being laid undersea were presented for several fields at Arctic basin condition: gas field Ludlovskoe, condensate field Leningradskoe and oil field Medinskoe sea.

Object and purpose of research. This paper discusses protective structure for a pneumatic test rig intended for experiments with the elements of underwater mining system at KSRC Open Test Tank. The purpose of this study was to justify the design parameters ensuring the safety in case of an emergency leakage from the tested equipment. Materials and methods. The study followed the methods of computer-based simulation to analyse gas dynamics of leakage escalation and its effect upon the protective structure. Main results. This paper presents development results of a floating submersible protective structure, with analytical estimates of hazardous factors and protection robustness in case of a hypothetical emergency during pneumatic tests of equipment. Conclusion. Protective structure design suggested in this paper for given conditions of submerging into an open tank and given conditions of pneumatic tests (pressure 69 MPa, nitrogen volume 1 m3) prevents hazardous leakage to the environment. Accordingly, these tests will be safe for both personnel and test facilities.

The underwater phase is perhaps the most important phase of the swimming start. To improve performance during the underwater phase, it is necessary to improve our understanding of the key variables affecting this phase. The main aim of this study was to identify key kinematic variables that are associated with the performance of an underwater glide of a swimming start, when performed at streamlined position without underwater undulatory swimming. Sixteen experienced swimmers performed 48 track starts and 20 kinematic variables were analysed. A multiple linear regression analysis was carried out to explore the relationship between glide performance (defined as glide distance) and the variables that may affect glide performance. Four variables in the regression model were identified as good predictors of glide distance: flight distance; average velocity between 5 m and 10 m; and maximum depth of the hip. The results of the present study help improve our understanding of underwater glide optimisation and could potentially facilitate improvement of overall start performance. pre-print 153 KB

Stingrays can undulate their wide pectoral fins to thrust themselves and swim freely underwater. Many researchers have used bionics to directly imitate their undulating mechanism and manufacture undulatory underwater robots. Based on the limitations of the existing undulatory underwater robots, this paper proposes a novel undulatory propulsion strategy, which aims to use the stingray undulating mechanism more thoroughly. First, the mathematical models of both traditional and novel structures are established to accurately describe their undulating mechanism. Then, based on the dynamic mesh technology, the flow field vortex structure they generated is analyzed through fluid-structure interaction simulation, and the thrust force and lateral force generated by them are calculated, which verified that this novel propulsion strategy is indeed more effective. Finally, a prototype robot based on the improved propulsion strategy is manufactured. Compared with the existing stingray robots, the prototype has obvious advantages, thus verifying the accuracy of the simulation results.

This paper presents a new simplified numerical approach (SNA) for predicting hydrodynamic data of underwater wings (UWs). Instead of full three-dimensional (3D) flow field analyses, SNA combines Vo...

В 3й части статьи рассмотрена методика моделирования разделок в геометрическом и аналитическом представлении. Базой методики является геометрическое моделирование, которое естественным образом позволяет идентифицировать поверхность разделки. По результатам идентификации формируется математическая модель в унифицированном виде. На завершающем этапе выполняется параметризация полученной модели. В качестве примера определено отверстие в сферическом участке корпуса в геометрическом виде и параметрическом уравнении в однородных координатах. Также в статье рассмотрен пример по определению изначального типа обрабатываемой поверхности в контексте предлагаемой методики. Благодаря модульной структуре методики процесс проектирования технологического комплекса можно начинать с любого его компонента и последовательно понижая неопределенность двигаться к законченному проектному решению. Исходными данными для формирования математической модели проектируемого технологического комплекса являются вид и параметры обрабатываемых поверхностей разделки кромок корпусов объектов подводного кораблестроения. The 3rd part of the article discusses the method of modeling cuts in geometric and analytical representation. The basis of the technique is geometric modeling. Which naturally identifies the cutting surface. Based on the identification results, a mathematical model is formed in a unified form. The final step is to parameterize the resulting model. Also the article discusses an example for determining the initial type of surface to be treated in the context of the proposed technique. Thanks to the modular structure of the methodology, the process of designing a technological complex can begin with any of its components and consistently reduce uncertainty and move to a complete design solution. Initial data for forming mathematical model of designed technological complex are view and parameters of processed surfaces of opening's bevels of hulls of underwater shipbuilding objects.

Background: In this paper, we present a completely new type of propulsion system where thrust force is created by the helicoidal shape of the hull rather than screw propellers. The method and device have been recently patented. The inspiration comes from nature, the world of bacteria, where some organisms have been using the drilling motion or rotating flagella to move in fluid media for several million years. The hull of device consists of three parts – bow and stern (which create the propulsion force) and the middle part which can serve as a cargo compartment containing all control mechanisms and communications. The Cardan-joint mechanism that allows changing the direction of the vehicle is actuated by bending drives. A bending drive velocity control algorithm is proposed for the automatic control of vehicle movement direction. Objective: Development of a new propulsion system for underwater vehicles. Methods: The watercraft dynamics were simulated using multibody simulation software MSC Adams. For accurate interaction with medium, polynomial metamodels were created on the basis of computer experiments with CFD software. Computational Fluid Dynamics software was used for flow interaction with the prototype geometry, implementing the same idea that is used in wind tunnel experiments. Results and Conclusion: The results are compared with measurements of the physical prototype, built at the Institute of Mechanics and Mechanical Engineering of Riga Technical University. These results showed good validation with mathematical simulation and confirmed the effectiveness and future potential of the proposed principle.

Underwater gliders are winged, autonomous underwater vehicles that are broadly applied in physical and biological oceanography. The position of the wing has an important effect on the movement performance of the underwater glider. In this paper, the dynamic motion of a series of underwater glider models with different longitudinal wing positions are simulated, which provides guidance for the design of underwater gliders. The results show that when the net buoyancy is constant, the wing position affects the gliding angle, but does not affect the relationship between the gliding angle and the gliding speed. In addition, the farther the wing position of the glider is from the buoyancy centre, the longer it takes for the attitude of a glider to change, whether the wing is in front of, or behind, the buoyancy centre.

Self-healing mechanism (SHM) application has attracted interest due to ability to self-heal as response to damage situations in various conditions, and is being actively explored. However, the application of SHM that can be autonomously triggered for temporarily keeping structural integrity of underwater robotic vehicle (URV) under flooding condition is still scarce publicly. This paper describes an investigation in watertight integrity performance of URV’s hull under damaged stability criteria. The main goal is to investigate the characterization of a rapid SHM through an experiment for identifying progressive flooding in a damaged URV’s hull. Here, it is demonstrated that the effectiveness of sodium polyacrylate, a kind of superabsorbent polymers (SAP), had been studied by applying the polymer on an experimental model of damaged URV’s hull. A comparison is studied for the stability of the flooded URV and the mass of water accumulated inside the URV’s hull between the cases of before and after applying the SHM in the damaged model under different damaged conditions. The results showed that the SHM application had rapidly blocked the damaged leak hole and prevented severe water flow ingress in the damaged URV’s hull. Swift recovery of buoyancy was obtained, as the volume of absorbed water by SHM was converted into equivalent buoyancy loss. These findings are establishing a fundamental knowledge for implementation of SHM in underwater robotic structures.

Propellers are a crucial part to drive underwater vehicles. A rim electromagnetic direct-driven propeller (REDP) had been presented to meet some specific requirements of the underwater vehicle in this paper. It had many advantages compared to classical propellers and could improve the performance of the underwater vehicle. The composition and working mode of REDP were introduced here. In addition, the paper also introduced the working characteristics of REDP and somethings needed to be improved. The energy method was utilized to calculate the distribution of magnetic fields. A three-dimensional model of REDP was built. Then the influence of the propeller’s parameters on performance was analyzed, including the number, pattern, surface radian of the permanent magnet and the stator cogging skew, by finite element computing models. The performances of REDP were tested under several parameters. Some valuable conclusions were obtained according the test results and could provide a reference for the design and performance optimization of REDP utilized on the underwater vehicle.

There is much need for autonomous underwater vehicles (AUVs) for inspection and mapping purposes. Most conventional AUVs use torpedo-shaped single-rigid hull, because of which their manoeuvrability is limited. Moreover, any increase in payload results in a larger hull size and the turning diameter, limiting its operation in constrained areas. As a solution to this problem, we develop M-Hull, a subsurface mapping AUV with a modular-split hull design that provides better manoeuvrability than a conventional torpedo-shaped vehicle. At the same time, it has more agility than an unconventional bio-inspired snake-like vehicle though their designs look similar. This approach makes it a hybrid solution between conventional torpedo-shaped AUVs and unconventional bio-inspired vehicles. We focus on improving the turning diameter during the mapping operation, and hence this paper concentrates on the dynamic aspects of the 2D turning motion of the vehicle. It will provide the relationship between turning speed, thrust, and joint torque requirements for the multi-hull underwater vehicle. Different turning modes are compared to choose an optimum turning configuration, and the critical speed is calculated for the vehicle’s safe operation. In the end, the modelling is verified using the experimental data. One can follow the method followed here for the 2D motion analysis of similar underwater vehicles.

The effect of underwater radiated noise (URN) pollution (produced by merchant ships) on marine ecology has become a topic of extreme concern for both the academic community and the general public. This paper summarises some research results and modelling about shipping noise published over several decades, which comprises the research significance of low-frequency ambient noise and shipping noise, shipping noise source levels (SL), empirical models and the measurement standards of shipping noise. In short, we try to present an overall outline of shipping noise and ocean ambient noise for related research.

The process of developing a mathematical model of the process of demining an explosive object located at depth is considered. Based on the above, the aim of the work is to develop a mathematical model of the emergency response process associated with the underwater location of an explosive object, as a process of functioning of the system "PNS - special means of underwater demining - diver-sapper", which should be the basis for -technical recommendations for improving the efficiency of underwater demining by divers. To solve this goal should solve the following main tasks: to determine the initial and boundary conditions for the functioning of the mathematical model; describe the process of underwater demining in the form of a multifactor model; to present options for the use of forces and means of underwater demining in the form of one-factor models; to determine the order of analysis of weighting factors in the obtained models. This task shows the feasibility of considering such a process in the form of a complex ergatic system "diver-sapper - special means of underwater demining - underwater location of an explosive object". simulation experiment, which will take into account the nonlinear influence of the components of the system, as well as their relationship with each other, on the effectiveness of underwater demining. It is shown that the mathematical model of underwater demining by a diver-sapper is a system of three analytical dependences. The first is a functional that describes the process of underwater demining in the form of a three-factor polynomial model. The second allows us to present this functionality as a set of one-factor models. The third provides the definition of weights in solving a multifactor problem. It is noted that such a model allows to proceed to the substantiation of operational and technical recommendations, which will take into account the impact (in that case nonlinear) not only directly of each individual indicator, but also the effects of interaction between them. Key words: emergency situation, underwater demining, multifactor assessment, operational and technical recommendations.

In an underwater compressed air energy storage system, fracture of the flexible riser often occurs. To solve this problem, we proposed a static analysis method for a flexible riser based on Cossera...

The predation behavior of the pistol shrimp is extremely special, and the predation process will produce a huge popping sound, which has caused extensive research by scholars from all over the world. This article carried out a study on the rapid closing jet mechanism of pistol shrimp’s claws. A theoretical model, based on the hydrodynamic characteristics of seawater and the theory of fluid-structure coupling, was proposed for the interaction between the claws and seawater. A simulation model was established using the finite volume software Fluent, and the rapid closing jet mechanism of pistol shrimp’s claws was verified by using fluid dynamic grid. This article studied the influence of different fluid models on the simulation results. The effects of the claws’ closing angular velocity and angular acceleration on the interaction between the claws and seawater were analyzed, which provides a theoretical basis for the development of new underwater kinetic energy weapons.

Interest in wave energy converters to provide autonomous power to various ocean-bound systems, such as autonomous underwater vehicles, sensor systems, and even aquaculture farms, has grown in recent years. The Monterey Bay Aquarium Research Institute has developed and deployed a small two-body point absorber wave energy device suitable to such needs. This paper provides a description of the system to support future open-source access to the device and further the general development of similar wave energy systems. Additionally, to support future control design and system modification efforts, a set of hydrodynamic models are presented and cross-compared. To test the viability of using a linear frequency-domain admittance model for controller tuning, the linear model is compared against four WEC-Sim models of increasing complexity. The linear frequency-domain model is found to be generally adequate for capturing system dynamics, as the model agreement is good and the degree of nonlinearity introduced in the WEC-Sim models is generally less than 2.5%.

Developments in underwater wet welding (UWW) over the past four decades are reviewed, with an emphasis on the re-search that has been conducted in the last ten years. Shielded metal arc welding with rutile-based coated electrodes was established as the most applied process in the practice of wet welding of structural steels in shallow water. The advancements achieved in previous decades had already led to control of the chemical composition and microstructure of weld metals. Research and development in consumables formulation have led to control of the amount of hydrogen content and the level of weld porosity in the weld metal. The main focus of research and development in the last decade was on weldability of naval and offshore structural steels and acceptance of welding procedures for Class A weld classification according to American Welding Society D3.6, Underwater Welding Code. Applications of strictly controlled welding techniques, including new postweld heat treatment procedures, allowed for the welding of steels with carbon equivalent values greater than 0.40. Classification societies are meticulously scrutinizing wet welding procedures and wet weld properties in structural steels at depths smaller than 30 m prior to qualifying them as Class A capable. Alternate wet welding processes that have been tested in previous decades — such as friction stir welding, dry local habitat, and gas metal arc welding — have not achieved great success as originally claimed. Almost all of the new UWW process developments in the last decade have focused on the flux cored arc welding (FCAW) process. Part 1 of this paper covered developments in microstructural optimization and weld metal porosity control for UWW. Part 2 discusses the hydrogen pickup mechanism, weld cooling rate control, design, and qualification of consumables. It ends with a description of the advancements in FCAW applications for UWW.

Coral reefs and all the life in them are one of the natural resources owned by the Indonesian people that are invaluable. Bontang city, located in East Kalimantan, is dominated by the ocean. Observation of the condition of coral reefs has been carried out by diving (diving) or snorkeling. For certain conditions, such as difficult locations, it does not allow humans to dive and observe directly the condition of coral reefs. This study proposes an alternative observation of coral reefs in Bontang waters using ROV. ROV is an underwater explorer robot controlled by an operator with a control device. The ROV in this study uses the arduino mega2560 as a controller, the BTS7960 module as a motor driver, MS5540CM sensor, motor as a driver. The ROV is equipped with a camera to take pictures and display them on a monitor. The results show that the ROV can work in the water, the ROV movement can be controlled and can maneuver well. ROV can automatically maintain depth when not operated with a range of ± 5 cm. The camera video system works well. The image captured by the camera can be displayed on the monitor in realtime. From the test results, it was found that the delay was less than 1 second between the image captured by the camera and the image displayed.

Purpose The inspection of flexible risers is a critical activity to ensure continuous productivity and safety in oil and gas production. The purpose of this paper is to present the design and development of a novel automatic underwater tool for riser inspection that fits the most commonly used riser diameters and significantly improves inspection quality and reduces its operating costs. Design/methodology/approach The mechanical and electronic design of the inspection system is discussed, as well as its embedded sensors and control system. The tool is equipped with a suspension system that is able to adapt to the riser diameter and negotiate obstacles on the pipe wall. Numerical simulations were carried out to analyze the mechanical design, and a hardware-in-the-loop simulation was developed for tuning the control system. Further, experimental results are presented and discussed. Findings Experimental tests in laboratory tanks and shallow seawater have confirmed the effectiveness of the tool for detailed real-time inspection of underwater pipelines. Practical implications The use of the proposed tool will potentially reduce the time and costs for riser inspection, currently performed by divers or high-cost ROVs. Originality/value The authors present a reliable tool able to perform automatic inspections up to 250 m deep in less than 30 min, equipped with a high-definition visual inspection system, composed of full-HD cameras and lasers and a suspension mechanism that can negotiate sharp obstacles in the pipe wall up to 25 mm high. The tool uses a comprehensive control system that autonomously performs a full inspection, collecting sensors data and returning safely to the surface. Its robust design can be used as basis for several other nondestructive techniques, such as ultrasound and X-ray.

Autonomous Underwater Vehicles (AUVs) are widely used for marine survey, in both the coastal and deep sea areas and they are applicable to both civil and defense applications. They are pre-programmed and can operate without human intervention and this makes them attractive to many marine industries. A concern with AUVs is the high energy consumption required by their thrusters for depth control, buoyancy change and manoeuvrability and that adversely affects their performance and endurance. This paper presents the design and development of novel stand-alone variable buoyancy system for AUVs and investigates its performance through numerical and experimental investigations. The design idea is based upon the Pump Driven Variable Buoyancy System (PDVBS) and uses a hydraulic based method to control the buoyancy. The VBS is integrated into a medium sized AUV of 3 m length and the performance of the vehicle in vertical plane is investigated. The results are presented for a buoyancy change requirement of 5 kg and a diaphragm type positive displacement pump, with a buoyancy change rate of 5 kg/min, is utilized. Depth control performance of the AUV and its hovering capabilities, at a desired depth of 60 m using the Linear Quadratic Regulator (LQR) controller, are analysed in detail. Finally, the results indicate that the designed and developed VBS is effective in changing the buoyancy and controlling the heave velocity. These two features are expected to provide higher endurance and better performance in AUVs involved in rescue/attack operations.

This study focuses on the prediction of the hydrodynamic and hydroacoustic performance of a cavitating marine propeller in open water condition using Reynolds-averaged Navier-Stokes (RANS) and Detached Eddy Simulation (DES) solvers. The effectiveness of the methods is investigated for the recently introduced benchmark propeller that belongs to the research vessel "The Princess Royal". The main emphasis of the study is to examine the capabilities of the RANS and DES solvers for predicting the hydrodynamic performance of a propeller in the presence of sheet and tip vortex cavitation (TVC). In the numerical simulations of the cavitating propeller flow, the Schnerr-Sauer cavitation model based on a reduced Rayleigh-Plesset equation was used to model the sheet and tip vortex cavitation. An alternative vorticity-based adaptive mesh refinement (VAMR) technique was employed for the accurate realisation of the TVC in the propeller's slipstream. In the hydroacoustic calculations, a porous Ffowcs Williams Hawkings equation (P-FWH) was employed together with the DES solver. The numerical hydrodynamic and hydroacoustic results are compared with those of experimental data for the benchmark propeller available from the University of Genova Cavitation Tunnel. The results show that both the RANS and DES solvers are successful for modelling of the sheet cavitation on the propeller blades. However, the prediction of the TVC extension using the RANS solver is found to be insufficient in comparison to the TVC prediction when using the DES method. This is due to the inherent modelling limitations of the RANS solver. In addition to hydrodynamic performance predictions, the overall noise spectrums were found in an agreement with the experimental data with discrepancies between the low and high-frequency region.