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The buoyancy of traditional Underwater Glider (UG) with a rigid hull is affected by the changing marine parameters, making it difficult for the vehicle to dive deeper with good motion characteristics. In the present work, the development of a novel UG for neutral buoyancy, which is equipped with a Flexible-Liquid-Rigid (FLR) composite hull, is presented. The innovative hull that imitates the buoyancy regulation mechanism of marine organisms is easily adaptable to the changing marine environment. The rigid part of the composite hull withstands hydrostatic pressure for inner function modules of the vehicle. The liquid of the composite hull mainly serves as a buoyancy compensation to mitigate the effect of buoyancy variation caused by the changing marine parameters. The flexible covering provides a good hydrodynamic shape for the vehicle under the internal liquid pressure. The buoyancy variation due to the composite hull compression as well as changes of seawater density and temperature was comprehensively considered in the design process and integrated to the dynamic model. In addition, sea trials were performed to verify the motion characteristics of the proposed vehicle. The results reveal that the Flexible-bodied Underwater Glider (FUG) has a better gliding performance in practice.

In this study, a model is developed to simulate the dynamics of an internal combustion engine, and it is calibrated and validated against reliable experimental data, making it a tool that can effectively be adopted to conduct emission predictions. In this work, the Ricardo WAVE software is applied to the simulation of a particular marine diesel engine, a four-stroke engine used in the maritime field. Results from the bench tests are used for the calibration of the model. Finally, the calibration of the model and its validation with full-scale data measured at sea are presented. The prediction includes not only the classic engine operating parameters for a comparison with surveys but also an estimate of nitrogen oxide emissions, which are compared with similar results obtained with emission factors. The calibration of the model made it possible to obtain an overlap between the simulation results and real data with an average error of approximately 7% on power, torque, and consumption. The model provides encouraging results, suggesting further applications, such as in the study on transient conditions, coupling of the engine model with the ship model for a complete simulation of the operating conditions, and optimization studies on consumption and emissions. The availability of the emission data during the sea trial and validated simulation results are the strengths and novelties of this work.

The extreme operational environmental conditions and aging conditions of subsea structures pose a risk to their structural integrity and is critical to their safety. Non-destructive testing is essential to identify defects developing within the structure, allowing repair in a timely manner to mitigate against failures that cause damage to the environment and pose a hazard to human operators. However, in order to be cost effective, inspections must be carried out without taking the risers out of service. This poses significant safety risks if undertaken manually. This paper presents the development of an automated inspection system for flexible risers that are used to connect wellheads on the seafloor to the offshore production and storage facility. Due to the complex structure of risers, radiography is considered as the best technique to inspect multiple layers of the risers. However, radiography inspection in turn requires a robotic system for in-situ inspection with higher payload capacity, precise movement of source and detector which is able to withstand an extreme operational environment. The deployment of a radiography inspection system has been achieved by developing a customized subsea robotic system called RiserSure that can precisely provide the scanning motion of a gamma ray source and digital detector moving in alignment. The prototype has been tested on a flexible riser during shallow water sea trials with the system placed around a riser by a remotely operated vehicle. The results from the trials show that the internal inner and outer tensile armour layer and defects in the riser can be successfully imaged in real operational conditions.

Underwater glider (UG) is widely applied for long-term ocean observation, the gliding range of which is mainly influenced by its design. In this paper, the design parameters that have obvious influence on the gliding range, including the buoyancy factor, compressibility of the pressure hull, hydrodynamic coefficients, and motion parameters, are selected based on the gliding range model of UG. Due to their complicate coupling relationship in the design of the UG, the multidisciplinary optimization (MDO) design framework integrating the collaborative optimization (CO) method and approximate model technology is adopted to optimize the key parameters by taking the gliding range as the optimization target. The results show that the optimization leads to an increase of the gliding range of Petrel-L as much as 83.3% when the hotel load is 0.5 W, which is verified by the sea trial. The optimization is applicable to other types of underwater gliders.

It is important to verify that the contracted speed–power performance of a ship is satisfied in sea trials. International Organization for Standardization (ISO) has published the procedure for measuring and assessing ship speed during sea trials. The results obtained from actual sea conditions inevitably include various uncertainty factors. In this study, double run tests were performed on one container ship to analyze the uncertainty of sea trial on three maximum continuous rating conditions. The uncertainty factors and scale of uncertainty were examined based on the measured raw data during sea trial. The results indicate that the expanded uncertainty for ideal power performance is approximately ±1.4% at 95% confidence level (coverage factor k = 2) and most of the uncertainty factors were because of the shaft power measurement system.

As well known, ships which have complex production processes are subject to various tests made on every stage in many fields from the beginning to the end of the production. After the tests are completed successfully, the ship is delivered to the ship-owner. “Sea trial” being the last stage of these tests, is examined in detail in this study. The purpose of this study is to plan the tests performed in the sea trial by the means of computer programs and to suggest shorter completion period for the tests.Thus, reducing the total cost ofthe cruising. Moreover, shortening the duration ofthe cruise will be a factor that can speed up the delivery ofthe ship. For this purpose, the tests and processes performed during the sea trial are listed. A cruise process flow diagram including all the tests applied under normal conditions was created, and the data were entered into the SIMIO simulation program. As a result, it was determined that the total cruising time was 28,0989 hours. After that, a new flow diagram was created by making some improvements in the current testing process, and a new simulation model was built up. In the new simulation model, total time spent to complete the tests were 25,3567 hours, so the testing time was shortened by 2.75 (9,76%) hours.

The calculation of total resistance value is important of ship because affects the speed of fluid flow that occurs, as well as the speed of the ship.So that in the designing new ships, sea trials are needed to find out whatever the preparedness of the ship is planned. The purpose is to obtain the value of the total resistance and the coefficient of ship resistance KM. Kendhaga Nusantara 6 uses the calculation method for each ship draught/loading condition. The Method used is experimental method with numerical value approach, Denny Mumford theory and Froude's number. The results show that the largest Total Resistance (Rt) is 5646,02 kN, it was found when speed of ship was 12 knots and draught ship 3,5 meters, with a coefficient value (Ct) of 7,757 x 10-3. The difference in value (Ct) is 0,032x10-3 or 0.41%, and it is still in the criteria because it is below 5%.

Small-scale ocean observations play an important role in oceanographic research. The station-keeping method based on the underwater mobile platform has been proposed as a means of small-scale ocean observation with the advantages of low cost and high flexibility. However, few studies have carried out complete modeling of the small-scale ocean observation process of mobile platforms and proposed a corresponding station-keeping method based on this. In this article, a hybrid underwater profiler (HUP) was tested under two working conditions for its ability of maintaining position during designated area persistent monitoring (DAPM) within a specific area of the sea over a long period. The DAPM problem is modeled and the cost function that evaluates the performance of DAPM is defined. If the underwater profiler cannot measure data about underwater currents, it can maintain its position by setting constant gliding and yaw angles based on the depth-averaged current measured each time it surfaces. If it has instruments to observe ocean currents at each depth during a dive, the profiler can maintain its position using a strategy based on a quasi-Newton method. Simulation results show that the gliding strategies effectively assist the HUP in monitoring a designated area. Additionally, sea trials were performed without instrumentation to measure ocean currents and the effectiveness of the simpler gliding strategy was clearly demonstrated.

The prediction of water current (WC) is key in understanding oceanographic phenomena, and serves as a corner stone for maritime applications. While numerical models are capable to characterize the main phenomenon effecting the current, a good estimate of the current’s velocity requires accurate environmental information such as topographic maps, temperature, and wind velocity. Without such information, common practice involves deploying a large number of drifting devices to measure the WC in good resolution. In this paper, we purpose a statistical approach to predict the WC’s velocity field, namely, the relation between the drifters’ locations and their drifting velocity to estimate the velocity of the WC across a given environment. We offer two statistical approaches. Assuming the above relation is linear, the first uses a weighted least squares to estimate the parameters of the velocity field. The second uses a support vector regression to predict the WC by a classifier. The first approach is more traceable, while the second can manage a non-linear space-speed relation of the WC. Results are studied numerically using an WC model, and experimentally from a sea trial performed across the shores of San Diego including 13 acoustically localized submerged drifters. In both cases, performances show a good agreement between the ground truth of the WC and the predicted one.

Typically, the dominant load for the design of planing hulls is slamming, while sailing fast at head seas. Slamming is a violent fluid-structure interaction, where dynamics, hydro-elasticity, and n...

Sea trial tests are necessary to verify speed-power performance, and are an import contract between ship owners and shipyards. The International Organization for Standardization (ISO) published ISO 15016:2015, which specifies the correlation method between model and full-scale ships. The results of sea trials have been questioned because of the uncertainty of speed and power measurements, especially when sea conditions differ from ideal calm water conditions. In this paper, such uncertainties were investigated by utilizing the standard speed-power trial analysis procedure defined in ISO 15016:2015 through Monte Carlo simulations. It was found that the expanded uncertainty of the delivered power (PDid) at 95 % confidence interval (k = 2) was ±1.5 % under 75 % MCR conditions.

The colonization of underwater environments by exotic seaweeds is causing major ecological problems around the world. This project, referred to AMALIA, aims to transform this current ocean threat into an opportunity by adding value to the macroalgae present off the northwest of the Iberian Peninsula. To do so and to observe the presence of seaweeds in situ, an ocean modular submersible platform was developed. This platform was designed to be capable of detecting and surveying surges of invasive seaweeds while withstanding sea conditions. Conceptual designs followed by a screening process were performed, taking into consideration criteria such as operational range and modularity. An open-frame lander was considered and further developed using buckling criteria. In parallel, a state-of-the-art monitoring system was created using spectral imaging, allowing for the future creation of a macroalgae identification system. In addition, sensorial systems for characterizing growth conditions were introduced. Laboratory trials were executed to assess the capability of the system, and sea trials are currently being performed. Numerical simulations and laboratory trials indicate that the structure is fully capable of being deployed for shallow-water environments with a state-of-the-art invasive seaweed monitoring system while maintaining a high degree of modularity.

The research addresses the problem of an ultra-large container ship mathematical model adjustment based on sea trials. In order to verify the model’s adequacy, simulated data had to be compared to the trial report data, which was obtained in ballast condition with significant trim. In such circumstances, model coefficients cannot be calculated by known methods and have to be corrected as per trial data. It is proposed to determine translational motion coefficients first. To get optimal results, it was also proposed to divide the objective function into kinematic and dynamic components, with each component being assigned a weighting factor. A separate objective function component was assigned to the zig-zag maneuver, which includes the first and second overshoot angles.

Autonomous underwater vehicles (AUVs) are programmable, robotic vehicles that can drift, drive, or glide through the ocean without real-time control by human operators. AUVs that also can follow a planned trajectory with a chosen depth profile are used for geophysical surveys, subsea pipeline inspection, marine archaeology, and more. Most AUVs are followed by a mother ship that adds significantly to the cost of an AUV mission. One pathway to reduce this need is to develop long-endurance AUVs by improving navigation, autonomy and energy storage. Long-endurance AUVs can open up for more challenging mission types than what is possible today. Fuel cell systems are a key technology for increasing the endurance of AUVs beyond the capability of batteries. However, several challenges exist for underwater operation of fuel cell systems. These are related to storage or generation of hydrogen and oxygen, buoyancy and trim, and the demanding environment of the ambient seawater. Protecting the fuel cell inside a sealed container brings along more challenges related to condensation, cooling and accumulation of inert gases or reactants. This paper elaborates on these technical challenges and describes the solutions that the Norwegian Defence Research Establishment (FFI) has chosen in its development of a fuel cell system for long-endurance AUVs. The reported solutions enabled a 24 h demonstration of FFI's fuel cell system under water. The remaining work towards a prototype sea trial is outlined.

Biofouling results in a range of adverse issues for ships and boats such as an increase in hydrodynamic drag force and fuel consumption and increased maintenance cost. To address this issue, toxic antifouling coatings have been developed. However, these toxic coatings can pose threats to marine life. This has led to research on less harmful techniques such as acoustic methods in the main implemented as laboratory trials. In fact, there have been relatively few sea trials and these are poorly documented. The current work has performed one of the few implemented field trials and the only one to be fully documented. In this sea trial, an optimised array of transducers generating ultrasound guided waves was attached to a hull representative plate in a port environment. The results of this work are evidenced by the significant reduction in-situ of a wide range of biofouling materials and organisms. The documented photographical evidence makes up for its scarcity in the published records of antifouling advances using acoustic techniques.

Underwater cable burying is one of main cable protection methods in the offshore cable installation. In this paper, the performance evaluation of an underwater cable burying robot, named URI-T, through the sea trial is addressed. URI-T, the first heavy-duty underwater robot for cable burying tasks developed in South Korea, is designed to perform burying tasks and maintenance tasks for underwater cables and small-size pipes at the sea bed of 2,500m water depth. URI-T includes water-jetting systems and cable detection sensors for cable burying tasks, and employes mainpulators and tools for cable maintenance tasks. The sea trial at the East Sea having 500m water depth was focused to verify the key performance indices: operation water depth, cable burying depth, cable burying speed, and forward speed. The cable maintenance ability was also examined by carrying out the cable cutting test and the cable gripping test. Moreover, applicability of URI-T is also evaluated by two times of cable burying experiments more than 100m distance. As a result, it was verified not only that URI-T satisfies the target performance indicies, but also that URI-T is applicable for the cable burying construction.

In 2018, a German- Dutch project consortium under the scientific direction of the Emden/Leer University of Applied Sciences retrofitted and commissioned the latest rotor development of the Eco-Flettner type on the test ship Fehn Pollux of the Leer-based shipping company Fehn Ship Management. Main design features are both upper and lower endplates with large diameter for improved aerodynamic performance and modular manufacturing. The retrofitting concept is groundbreaking in terms of easy transferability to other ships. Upscaling to a significant share of the world merchant fleet could make a substantial and realizable contribution to climate protection in the short term and potentially reduced transport costs in the long term. The most frequently asked question in connection with modern sail drives is about the performance potential and the associated fuel savings. Transparent performance data is required to enable an economic prognosis for the use of Flettner rotors on ships. The Faculty of Maritime Sciences at Emden/ Leer University of Applied Sciences has developed an automatic control and monitoring system for Flettner rotors that also records extensive operating and environmental data. The data shows that all previous assumptions and model calculations are basically correct. With regard to the performance potential, the first series of measurements show even higher rotor forces compared with model calculations. This is a further benefit for Flettner rotor efficiency and could help the technology achieve a breakthrough as a building block for low-emission shipping.

Small fast passenger boats serve to carry passengers at certain routes particularly in short distance between the islands. The passengers preferred those transport modes due to its short travel time. In fact, there are many accidents occur during boat operation which end up with the loss of life and materials at sea. An intensive study was executed by the authors with the purpose to obtain an unsinkable boat. The boat data of existing boats were collected and be used for re-designing process. During the design process, some solid boxes, expanded bags were provided inside boat to reduce the incoming water. Meanwhile, the bags were fitted outside the boat (side floater) to provide additional buoyancy and righting moment for stability performance. A boat model was developed and tested to confirm the design results. In addition, a full-scale boat was developed and equipped with solid boxes, air bags and side floaters. The theoretical computation and extrapolated results from model proved that the required volume for inside solid boxes and air bags are 1.213 m3 and 0.511 m3 respectively. Meanwhile, the required volume of outside air bags is 0.357 m3. It was found that the total boat weight, passengers and incoming water of 4.259 tons are balanced by weight displacement of 5.025 tons. There was reserve buoyancy of 0.766 tons that supports the boat to be float and side floaters to prevent the boat from capsize. The result of sea trial showed that with all loading conditions the boat was still afloat (unsinkable).

IMO’s resolution No. A. 751 on ship manoeuvrability was adopted in 1993. Sea trial data performed in Korean ship yards are collected and analized based on the standards for the ship manoeuverability. In this paper, the results are presented and checked whether the criteria in the standards are strict or not for usual ships. Some suggestions derived from the analysis of data base and the application of the criteria are given.

As the offshore energy sector looks to fully implement resident, autonomous, robotic, digital systems offshore, one missing piece of the puzzle is remote power generation. Further complicating these efforts are the owner/operators’ move towards net zero operations. The combination represents a significant dilemma for the offshore energy industry: if gensets and topside vessels are not appropriate or practical power sources for future resident systems, how will these needed cost and carbon-saving innovations come to market and get deployed in the field? Objectives/Scope The proposed paper will provide an overview of a new platform solution, an autonomous offshore power system (AOPS), that looks to complete the puzzle. A number of AOPS’ are under development world-wide. The paper will review the state-of-the-art, including the SeaRAY AOPS, which will undergo sea trials off the coast of Marine Corp Base Hawaii, on Oahu, Hawaii, USA. The sea trials are expected to last for six months. Note: Because of COVID-related delays, the sea trials originally planned for late 2020 will now start in 2Q21. The August presentation at OTC will include the latest information available on the sea trials and co-deployed payload testing. Methods, Procedures, Process The SeaRAY AOPS is the result of a project co-sponsored by the U.S. Department of Energy, U.S. Navy, and C·Power, to design, build, and test a novel AOPS technology. The SeaRAY AOPS provides kW-scale power generation, energy storage, and real-time data and communications capabilities for remote, offshore systems, including unmanned subsea and surface vehicles (e.g., AUVs, ROVs, USVs), sensor payloads (e.g., environmental monitoring or methane emissions) and operating equipment (e.g., emergency power for failed/failing umbilical, field modernization, or redundant power for BOP systems). Satisfying the need for cleaner operations, the SeaRAY and other AOPS devices capture and convert ocean energy into electricity to charge the energy storage system. The payloads, in turn, receive their power from the intermediate energy storage system, allowing campaign-based or extended residency. Results, Observations, Conclusions The paper will review the initial results from the planning, permitting, deployment, operation, and maintenance of the SeaRAY AOPS and the co-deployed sensor and vehicle payloads, which include a seafloor acoustical environmental monitoring system and a hybrid AUV. Novel/Additive Information: The market impact of AOPS’ for the offshore energy industry can be significant, as the class of systems is intended to enable reductions in operational costs, carbon emissions, and complexity, while enabling a fuller implementation of autonomous and semi-autonomous resident systems. The paper will outline these features and benefits for the offshore energy industry, along with the results to-date of the novel SeaRAY AOPS’ sea trials.

The exploration of the Micro-topography and landforms in the abyss area is one of the main application directions of manned submersible. It is of great significance to use the Bathymetric Sidescan Sonar System of manned submersible to obtain high resolution topography and geomorphology map of abyss area. This paper introduces the composition and working principle of Bathymetric Sidescan Sonar System and key technology of Jiaolong manned submersible after the upgrade of Jiaolong manned submersible. Combined with the data obtained from sea trial and scientific application voyage of Jiaolong manned submersible, the advantages of underwater vehicle automatic navigation technology in the exploration of topography and geomorphology in the abyss area are analyzed, combined with the subjective initiative of human. The Bathymetric Sidescan Sonar System could still work in the best condition. This paper also discusses the interference of digital underwater acoustic communication system on the mapping of Bathymetric Sidescan Sonar System. Finally, the detection results of the line stations are given. It provides a reference for the application of Bathymetric Sidescan Sonar System for manned submersible in the exploration of micro topography and geomorphology in the abyss area.

Tidal current energy is a promising renewable energy resource. Full scale tidal current turbines (TCT) have been deployed all over the world. To verify the design methods of large TCTs with high reliability and efficiency, a 600-kW tidal current turbine was designed and tested in this study. This turbine consisted of a two-blade rotor, a low speed ratio gearbox and a medium speed generator. The turbine was grid-connected through a full-rated converter, and its speed was controlled to capture the maximum power. First, to reach high turbine performance, system design details and maximum power point tracking (MPPT) control strategy were considered. Then, the 600-kW turbine was manufactured, and an onshore test was carried out to test power transmission and control performance. The power performance of the blades and control system were further tested in the sea trial carried out in Zhoushan. Good agreement was obtained between theoretical analyses and test results. Finally, to ascertain causes for observed power fluctuations, the power spectral density (PSD) was analyzed; the results indicated that power fluctuations may be due to stream shear.

In this paper, wave-induced motions and loads of a bow flare ship advancing in harsh irregular waves are investigated both numerically and experimentally. A 3D time-domain hydroelasticity theory that includes memory-effect function considering Froude–Krylov nonlinearity is developed to predict ship motions, wave loads and slamming loads in long-crested irregular waves. In the hydroelasticity algorithm, the wave memory effects and forward speed effects are addressed by retardation function method to improve the computing efficiency and provide opportunity for short-term statistical analysis of ship responses in irregular waves. In addition, segmented model tank tests are conducted to experimentally investigate the motions and loads of ship sailing in long-crested irregular waves and also validate the numerical results. To further understand the nonlinear wave loads behavior of ship in short-crested waves, large-scale segmented model sea trials are performed in realistic sea waves. The numerical results and experimental results are systemically analyzed and compared using time series, spectral and probability statistical analysis methods.

When burying underwater cables using robots, heading control is one of the key functions for the robots to improve task efficiency. This paper addresses the heading control issue for URI-T, an ROV for underwater construction tasks, including the burial and maintenance of cables or small diameter pipelines. Through modeling and identifying the heading motion of URI-T, the dynamic characteristics and input limitation are analyzed. Based on the identification results, a PD type controller with appropriate input treatment is designed for the heading control of URI-T. The performance of the heading controller was verified in water tank experiments. The field applicability of the proposed controller was also evaluated through the sea trial of URI-T at the East Sea, with a water depth of 500 m.

We develop the approach to simulate the experiments with surface and underwater vehicles in towing tanks for Reynolds numbers Re, corresponding to sea trials, using discrete injection of polymer additives. The complete dynamic similarity between full-scale and tank tests is possible if both Froude number and Re are equal for a ship and its model. In traditional experiments, the first condition is only satisfied and the viscous and wave resistances are independently studied. The Toms effect is widely used in marine engineering, e.g., to reduce energy cost. In this work, it is applied quite differently. Re is higher and the skin friction coefficient c f is hence less for sea trials than for towing tanks. Injection of polymer additives allows decreasing c f on ship model to full-scale values, providing the complete similarity and reproducing sea trials in that way. We report the selected results of such novel approach that, in particular, include velocity profiles and c f for sea trial, towing tank and pipe experiments, plane boundary layer and 3D flow around propeller, rough and smooth surfaces. The data for full-scale and tank experiments agree well with each other.

The unmanned wave glider (UWG) is a new kind of wave powered unmanned marine vehicle for persistent marine environment monitoring. However, the heading control of UWG is unusual, mainly about the heading control of the surface float body (Float), since it is indirectly actuated and with a large lag of the control response. The adaptive heading control method for the Float with heading information fusion is discussed. The basic and improved arrangement methods of the desired heading of Glider are proposed. Via direct heading control of Glider, the heading control of Float is realized indirectly. Simulation and sea trial results demonstrate that the proposed adaptive heading control method improves the heading control performance of UWG significantly.

Ultrashort baseline positioning systems are used to localize manned deep-sea submersibles. A long baseline positioning system is a significant supplement to an ultrashort baseline positioning system and provides more precise positioning. The long baseline beacon array design applied is a primary factor affecting the accuracy of long baseline positioning. However, beacon array designs have mainly been studied in autonomous underwater vehicles (AUVs). Because the characteristics and dive tasks between AUVs and manned deep-sea submersibles are different, the simple beacon array formations used in AUVs cannot be directly used in manned deep-sea submersibles. To the best of our knowledge, this study is the first to present the optimal design of a beacon array for a long baseline positioning system used in manned deep-sea submersibles. In this paper, based on the characteristics of a manned deep-sea submersible, the seven basic principles used for the optimal design of a long baseline beacon array are presented. First, the dive tasks of a JIAOLONG manned deep-sea submersible are analyzed, including the relationship between the dive survey lines, and the depth and distance of each line. Second, we explore the minimum beacon number to cover the dive site and its vicinity. Third, we adjust the beacon position based on the seven optimal design principles. The beacon array is designed to satisfy manned deep-sea submersible dive requirements during the JIAOLONG Test Applications Voyage 2013. A sea trial demonstrates that the long baseline positioning results are reliable if at least three beacons are not blocked, and the accuracy of the long baseline positioning system is better than that of an ultrashort baseline.

In towed sonar systems generally, the array is towed behind a ship using a combination of electro-optic mechanical (EOM) tow cables - negatively buoyant metallic armoured Heavy Cable and neutrally buoyant fibre armoured Light Cable- the former for depth control and latter for depth maintenance. Any failure in these cables can affect the performance of the sensor array and can even result in loss of the towed system to sea. During a series of towed array trials, it was observed that the metallic armoured cable had lost its circularity and became flattened during deployment and retrieval from ship. This may be due to the extreme radial forces acting on the cable while passing through a) rollers located at winch spooler and b) main fairlead comprising of 5 rollers located at aft end of ship, which causes permanent changes in cable’s internal configuration. To verify the cause and study the effects of such flattening on functionality and life of the cable, cyclic load testing studies were carried out after simulating the actual deployment-retrieval conditions as that in the ship. Both indigenously developed and imported cable samples were chosen as test samples for performance comparison. During the tests, it was observed that severe flattening of armour and core cable resulting in failure of electrical & optical lines had occurred in indigenous cable samples. The imported cable samples showed no flatness or failure of lines. Based on the results, steps were taken to improve the radial load bearing capacity of the indigenous cable. Modifications were made in a) core cable sheath material b) core cable sheath thickness & c) armour wire material and an improved indigenous cable was developed, which has withstood all the above tests and is now ready to be inducted to the system for sea trials.

Wave-induced ship motion and load responses are usually investigated on the assumption that the incident waves are long-crested. The realistic sea waves are however short-crested irregular waves. Real practice reveals that the ship motion and load responses induced by short-crested waves are different from those induced by long-crested waves. This paper aims to conduct a comprehensive study on ship motions and loads in different wave fields. For this purpose, comparative studies by small-scale model towing tank test and large-scale model sea trial are conducted to experimentally identify the difference between ship motions and loads in long-crested and short-crested irregular waves. Moreover, the influences of directional spreading function of short-crested waves on ship motions and loads are analyzed by numerical seakeeping calculation. The results and conclusions obtained from this study are of great significance for the further extrapolation and estimation of ship motions and loads in short-crested waves based on long-crested wave response results. Keywords: Short-crested wave, Directional spectrum, Motion and load responses, Seakeeping performance, Hydroelasticity theory

A newly built ship must conduct sea trial to understand its performance including speed, maneuverability and so on. The result of the speed trial is very important for the ship owner, because the ship speed is directly related to profit. In this case, current becomes an important factor because the ship speed is changed by the effect of the current. To remove this effect, International Towing Tank Committee and International Organization for Standardization heve presented procedures of removing this effect. However, these procedures require two or three round–trips against one ship speed. To solve this difficulty, we attempt to estimate herein the current from the ship motion based on successive data assimilation. The proposed method is verified by twin experiments. Consequently, the proposed method is found to estimate the current well.

Prediction of the dynamic behavior of autonomous underwater vehicles (AUVs) is the basis for developing the control system and optimizing the hydrodynamic shape of AUVs. A fast and efficient prediction method of dynamic behavior of AUVs was developed with the secondary programming of a commercial computational fluid dynamics (CFD) code of FLUENT. In the proposed CFD method, mass properties of the AUV and thrust of the propeller were coupled to the 6-degree-of-freedom (DOF) dynamic equations of AUV in the form of user defined functions. A subregional unstructured mixed meshing strategy combining static meshes and dynamic meshes was proposed to improve the computational efficiency and to realize the 6-DOF movement of AUV. The proposed CFD prediction method can predict not only the dynamic behavior of the AUV, but also its surrounding flow field. Dynamic behavior of a seafloor mapping AUV in straight running and turn running were predicted using the developed CFD strategy. Comparison between the prediction results from the CFD method and those from the sea trials proved the proposed method to be accurate and effective. Some measures were put forward to improve motion performance of the vehicle according to the prediction results.

A comparison between sea trial measurements and full–scale CFD results is presented for two self–propelled ships. Two ships considered in the present study are: a general cargo carrier at Froude number Fn=0.182 and a car carrier at Fn=0.254. For the general cargo carrier, the propeller rotation rate is fixed and the achieved speed and trim are compared to sea trials, while for the car carrier, the propeller rotation rate is adjusted to achieve the 80% MCR. In addition, three grids are used for each ship in order to assess the grid refinement sensitivity. All simulations are performed using the Naval Hydro pack based on foam-extend, a community driven fork of the OpenFOAM software. The results demonstrate the possibility of using high–fidelity numerical methods to directly calculate ship scale flow characteristics, including the effects of free surface, non–linearity, turbulence and the interaction between propeller, hull and the flow field. Keywords: Full scale ship propulsion, Actuator disc, Sea trial validation, Grid sensitivity studies, OpenFOAM

In the 2nd term SIP project (SIP2), “Innovative Technology for Exploration of Deep Sea Resources” in Japan, National Maritime Research Institute, NMRI, is promoting the AUVs control system construction initiatively together with the leading agency, Japan Agency for Marine-Earth Science and Technology, JAMSTEC. To promote future high-level formation control, two types of fundamental formation control tests were tried using two AUVs and one ASV in the sea. One of them is virtual leader-follower control, and the other is centralized AUV control by one ASV. Seafloor topography mapping at the coast in Japan was successfully conducted by the two control methods with AUVs as test trials. In this paper, the results of the fundamental formation control tests of them are reported and summarized. Detailed consideration of the test results is represented using a simple simulation of AUVs in the latter half of this paper. Moreover, the plan for the promotion of the formation control system that will be done in near future is introduced.

ROV trencher is a kind of ROV which trenches the sea floor using a specifically designed tool and buries the subsea cables and pipelines. According to the soil conditions, this trenching method can have two different types, one is mechanical cutting and the other one is water jetting. In this paper, we present a water jet tool design method for a 2500 m depth-rated ROV trencher. A series of CFD simulations and laboratory tests with one nozzle, and a ground test using 1:6 scale jetting arm model were carried out to derive and demonstrate the jetting tool design parameters. In October 2018, the constructed ROV trencher was put into the sea trial in the East Sea of Korea to evaluate its final performances. In addition, in December 2019, the trencher was applied in a construction site to bury subsea water pipelines near the Yogji Island in the Korea. Through these two field tests and operation, the trencher was demonstrated for both its operational capability and trenching performance. The main contribution of this paper is that it presents the entire design procedures of water jet tools, including CFD simulations, laboratory tests, field test with 1:6 scaled jetting tool, and the final prototype tool design. These consecutive procedures are carried out in order for us to set up sort of relationship between jetting angle, trench depth, trench speed, and jetting power, from which we can predict and evaluate the trenching performance of the prototype jetting tool.

The Gate Rudder is a recently introduced twin rudder system whose major advantages stem from its energy-saving properties. The two foil-shaped blades of the rudder, placed aside of the propeller, act as a partial duct in the wake of the hull producing additional thrust. However, since the rudder is a primary safety device on any vessel, investigating the manoeuvrability performance of the Gate Rudder is a critical aspect that needs careful and detailed consideration. Owing to its peculiar working principle and location, the standard manoeuvrability prediction methods cannot produce reliable results since they are applied to rudders acting behind the propellers. This paper presents the first comprehensive investigation into the manoeuvrability performance of a Gate Rudder system, which includes the development of a modified MMG model, towing tank experiments and full-scale measurements. The modified MMG model was conceived to predict the manoeuvring motions of a ship with the Gate Rudder system. A generalised prediction method is defined based on this modified MMG model and detailed CFD analysis of the flow pattern around the Gate Rudder for two commercial hull-forms. The simulation model of the Gate Rudder is validated by means of towing tank tests and full-scale manoeuvring trials. The sea trials were conducted onboard two sister container vessels, the first fitted with the first-ever Gate Rudder system and the second with a high-performance flap rudder. This also allowed to compare the two different steering systems.

Unmanned and autonomous navigation is a promising area for the development of water transport. In the past few years, unmanned and autonomous ships have been actively operating, performing various industrial tasks, for example, hydrographic surveying. However, for this type of equipment, it is necessary to conduct tests to determine that the safety of such water transport will remain at a given level during operation. Maneuvering and sea trials of ships with a crew on board are performed by giving commands by the captain or another person conducting the trials, but this is not possible for unmanned and autonomous ships. Thus, the purpose of the work is to develop a method for conducting a series of sea trials of unmanned ships to determine the limiting technical capabilities of the ship during its movement and maneuvering. The method is based on the normalization of a set of ship movement parameters measured by an independent method and independent equipment at test ranges, where it is possible to carry out all the necessary types of trials for unmanned ships. The ship moves along a predetermined route that has straight and radius sections with a gradual complication, which consists in a gradual reduction in the length of straight sections and a decrease in radius sections of the turn. Thus, the control of the movement of unmanned or autonomous ships differs significantly from the traditional control of a ship, and new methods are required for conducting sea and maneuvering trials of unmanned or autonomous ships, one of which is proposed in this work. This method is designed for use at test water areas, where it is possible to carry out all the necessary types of trials on unmanned ships.

This paper describes a simplified method to modeling and parameters identification of an Unmanned surface vehicle USV. The USV is propelled by two thrusters allowing both control of speed and heading. The outputs of the studied system are variables that characterize the kinematics and the motion of the USV such as the speed, the heading, and the position in the horizontal plan. First a nonlinear model with three degrees of freedom is designed, then the parameters are calculated based on sea trials data. Finally the model is validated by simulation in order to perform some control methods in a future work.

This paper introduces the development, sea trial and application of a new type of underwater vehicle, Haidou, the first underwater vehicle in China diving to a depth of more than 10000 meters and serving for the national full-depth ocean scientific exploration, with the goal of being capable of reaching to the deepest area of the whole global ocean and collecting the surrounding parameters and video data there. For the hadal trench exploration up to 11000 meters, the concept of ARV technology is proposed, and the parametric modeling and multi-objective optimization design methods are used for the purpose of verification of full-depth ocean technology and highly efficient deep-sea detection ability. The vehicle named as Haidou was developed eventually, and field trials were carried out in Mariana Trench during the first comprehensive scientific expedition of China in 2016. With new mission, Haidou came back to the Challenger Deep of Mariana Trench at the beginning of 2017, Thanks to this micro cable with a length of 40 km, the ARV operation approach of Haidou combine the AUV mode under human supervision with the ROV mode capable of being tele-operated at the bottom of the deepest area in global ocean, and made it possible that the operators on the mother ship can obtain environmental data including the real-time optical video of the unusual deep sea bottom with the real-time remotely control for more than 4 hours. In the near future, Haidou will play a more important role in the national hadal trench scientific exploration.

This paper addresses the challenges and advances made in the hydrodynamic design and design evaluation of ducted propellers. The application of new ducted propeller analysis tools is shown for the practical case of the design of controllable pitch propellers for hopper dredgers. Results of model tests and sea trials are compared with results of a state-of-the-art boundary element method (BEM) code that is used for the simulation of the unsteady cavitating flow around ducted propellers. The results of the BEM simulations are compared to more time consuming and comprehensive URANS sliding interface calculation results in which the flow including the unsteady flow around the rotating propeller is modelled in the RANS domain. Comparisons are made of pressure distributions and pressure side cavitation margins that are important in the propeller blade design. The details of the flow into the duct are discussed as well as its implications on the propeller blade design. The employed BEM method is proposed as the best practical next step in ducted propeller design given its reasonable calculation times. Based on the obtained results a new research initiative has been started to obtain better sea trial data from ducted propellers to improve and validate the ducted BEM method as well as the SI URANS method.

This paper describes the development of an underwater fin-type robot that can swim along a given path with localization and walk on the seabed to inspect the seabed precisely. Oscillating fin systems were designed to generate enough thrust considering the dynamics model of the robot. Then, methods for basic movements, path following, and seabed missions were proposed. Sea trials demonstrated the capability of basic motions, such as surge, heave, and yaw, with localization. Moreover, it appeared that walking on the seabed is also feasible, depending on the fin design and the fin oscillation.

This paper mainly introduces Explorer 1000 AUV, a class of long-range AUV, which is newly developed by Shenyang Institute of Automation, CAS. Explorer 1000 is designed to dive to 800 meters underwater for ocean survey and has a 1000 km work range at a speed of 2 knot. Additional, Explorer 1000 AUV has two high-precision variable buoyance systems(VBSs). So it can execute two work modes: fixed-point observation mode that AUV carries out reciprocating profile observation in certain fixed position, and cruise & observation mode that AUV cruises multiple observation points and carries out fixed-point observation at each point. A lot of works have been done to increase the range and endurance of AUV while designing. Finally, Finally, the Yellow Sea trial results are shown to prove the fundamental performances of Explorer 1000 AUV.

International audience; This paper presents sea trials on a 6-m boat specifically designed for kite propulsion. The kite control was automatic or manual, dynamic or static, depending on the point of sailing. The measurement system recorded boat motion and load generated by the kite. A particular attention was paid to wind measurement with several fixed and mobile locations directly on the kiteboat or in the vicinity. A high resolution weather modelling showed that a classical power law, describing the wind gradient, was not satisfactory to get the wind at kite location. 5-min measurement phases were systematically recorded. In the end, 101 runs were carried out. Data were processed with the phase-averaging method in order to produce reliable and accurate results. © 1996-2020 MDPI (Basel, Switzerland) unless otherwise stated

Existing recommended practices in the literature do not provide clear and concise guidance for the selection of the most suitable numerical modelling strategy for investigating the boundary layer around a ship at full scale. For example, the International Towing Tank Conference procedure for calculating the nominal wake fields of full-scale ships does not clearly specify which turbulence modelling approach should be used to accurately represent the near-wall flow in the ship's aft region. This paper presents a numerical approach that can accurately represent the boundary layer of full-scale ships. Three turbulence modelling strategies, suitable for the simulation of ship flows, have been assessed: k-e, k-ω SST RANS and an IDDES formulation. Results from each method have been compared against the full-scale ship propeller torque data of the MV Regal, a 138m long general cargo vessel. Additionally, the capability of each turbulence strategy to resolve time-dependent features of the flow, such as the bilge vortex and its effect on the boundary layer velocity fields, has been evaluated. The results from this investigation show that the IDDES based numerical model replicated the sea trials measurements with the highest degree of accuracy. Furthermore, this study confirmed that the choice of turbulence strategy has a major impact on the full-scale velocity fields in the aft region of a ship.

Aiming at the poor accuracy and difficult verification of maneuver modeling induced by the wind, waves and sea surface currents in the actual sea, a novel sea trials correction method for ship maneuvering is proposed. The wind and wave drift forces are calculated according to the measurement data. Based on the steady turning hypothesis and pattern search algorithm, the adjustment parameters of wind, wave and sea surface currents were solved, the drift distances and drift velocities of wind, waves and sea surface currents were calculated and the track and velocity data of the experiment were corrected. The hydrodynamic coefficients were identified by the test data and the ship maneuvering motion model was established. The results show that the corrected data were more accurate than log data, the hydrodynamic coefficients can be completely identified, the prediction accuracy of the advance and tactical diameters were 93% and 97% and the prediction of the maneuvering model was accurate. Numerical cases verify the correction method and full-scale maneuvering model. The turning circle advance and tactical diameter satisfy the standards of the ship maneuverability of International Maritime Organization (IMO).

In this paper, we discuss underwater walking robot technology to improve the quality of raw data in sector-scanning sonar images. We propose a strategy for an efficient and precise sector-scanning sonar image acquisition method for use in shallow, strong tidal water with a curved and sloped seabed environment. We verified the strategy by analyzing images acquired through a sea trial using the sector-scanning sonar installed on the CRABSTER (CR200). Before creating this strategy, an experiment was conducted to acquire the seabed image near a pier using a tripod and vertical pole. To overcome the problems and limitations revealed through image analysis, we established two technical strategies. In conclusion, we were able to achieve those technical strategies by using the CR200, which is resistant to strong current, and its six legs provide freedom of movement, allowing for a good sonar attitude.