Journal of Ocean Technology

Published by Memorial University of Newfoundland, Fisheries and Marine Institute, Centre for Applied Ocean Technology
Energy efficiency is a crucial issue in ship management and operation. A proper fuel saving oriented routing strategy can be helpful in reducing running costs and pollutant emissions, as well as increasing the voyage safety and comfort. This paper presents a methodology for ship voyage planning based on 3D dynamic programming. It aims to select the optimum courses and related speed profile for a ship voyage in accordance to a minimum fuel consumption strategy, on the basis of the ship response to wave and wind conditions inferred from weather forecast maps. The ship voyage is parametrized as a multi-stage decision process where the fuel optimization is carried out in a discretized space-time domain and the optimal solution, in relation to the arrival time requirements and motion related constraints, is found by a dynamic programming algorithm which has been developed and implemented by the authors. Simulation trials for a merchant ship sailing different typical routes in the Mediterranean Sea, in a wide range of weather conditions and using high quality weather forecast maps, are presented and discussed. With respect to previous authors’ publications, the presented methodology shows the high potential benefit of detailed weather forecast maps as well as the innovative use of a minimum distance algorithm.
The challenge of underwater positioning continues to limit our capability to explore, understand and operate in the marine environment. Positioning solutions that use time-of-flight acoustic range measurements have been a standard for underwater navigation for over thirty years. Advances in estimation techniques and the increased performance of navigation instrumentation have improved our ability to localize underwater assets, but a reliance on acoustic time-of-flight range measurements persists. Modern navigation solutions provide a real time six degree-of-freedom state estimate, fusing observations from a variety of complementary and redundant proprioceptive sensors. Designing such an integrated navigation system requires an analytical framework for predicting the systemlevel performance based on the precision and configuration of the individual components. We present an analytical tool for predicting the quality of the overall navigation solution based on the uncertainty in all the constituent measurements and the geometry of the acoustic elements in the system. This solution is applicable to a wide variety of acoustic ranging applications, including basin-scale positioning of drifting floats based on time-of-arrival measurements, long baseline (LBL) positioning and compact, short baseline solutions. This estimation framework is based on the Cramér Rao lower bound (CRLB) combined with the notion of dilution of precision, adopted by the global positioning system community, to quantify these tradeoffs. The advantage of this approach is that it incorporates all the navigation sensors as information sources, allowing for quantitative tradeoffs based on how the individual components impact the overall system performance. The result is a general purpose predictive tool for designing integrated navigation solutions. To illustrate this general tool, we present quantifiable answers to a few pertinent questions for the design of modern, multi-instrument navigation solutions which include acoustic time-offlight range observations: • How does the geometry (constellation) of acoustic elements affect the overall positioning uncertainty? • When using odometry instruments, such as a Doppler velocity log (DVL), what is the sensitivity of the overall positioning precision with respect to the uncertainty in velocity, range and survey measurements? • How does the temporal update rate for each instrument in the navigation solution affect the system-level localization performance? • What is the relative importance of heading, odometry and range precision for overall performance? Finally, we validate our estimation framework with controlled field tests using a next generation high-precision LBL sensor. This instrument provides sub-centimetre timing precision over ranges in excess of 300 metres and provides an ideal test case for verifying the results of our predictive model.
Providing energy to an underwater sensor network has always been a challenge due to the rough condition at sea as well as the lack of access to deployed equipment for battery replacement. Moreover, the lack of solar energy excludes the use of solar cells in cold oceanic regions. In such harsh conditions, maximizing sensors’ life time is an essential goal. In the area of ocean current measurement, some of the existing methods are mostly limited to measure only the surface current and not the shallow water current, while some other methods measure the speed of water in a vertical column only at one location. There are other systems that measure and store the current data of different locations and depths over time (few days) so the current data saved in them are not real-time. This study aims to overcome some of these limitations and proposes a real-time measurement method for wide area averaged current. Thus, in this paper, novel underwater sensor network topologies and architectures have been designed and proposed. These new proposed architecture designs specifically aim to maximize the network lifetime by minimizing the energy demand of the whole network. For this purpose, two types of network topologies, Hexagonal and Square, with two different configurations of with- and without-centre node for each type, have been designed and offered. The method used in the current measurement networks is based on transit time method and could be considered a modified version. Using the new modified measurement method, these novel architecture designs unravel the limitations of the existing current measurement methods. In this paper, the proposed architecture designs’ performance has been compared to each other and also their pros and cons have been discussed.
It is long established that the East African Coastal Current flows northward along the coast of Tanzania throughout the year. However, uncertainty has long existed as to the influence of this current in the Zanzibar Channel. Victims of various capsized vessels within the channel have been picked up both to the south and north of the accident site depending on the monsoon period. Current monitoring and measurements have recently been made in the Zanzibar Channel with the view to understanding the flow structure within the channel. In the first campaign measurements were made during both the Northeast and Southeast monsoon periods along a cross-channel transect using a lowered Aanderaa (RCM9) current meter. In the second campaign an upward-looking Acoustic Doppler Current Profiler (ADCP) was deployed at one station for two years to capture variations in the current profile over both monsoon periods. In the central, deeper part of the channel the current was found to flow northwards at all depths during the Southeast monsoon period with surface velocity of 0.5 ms-1. During the Northeast monsoon period, however, the current was found to flow southwards at the surface while a northerly flow continued close to the bottom. Away from the central part of the Channel, the two year ADCP data showed that the flow was northeastwards throughout the water column and reversed during the Northeast monsoon months of December, January, February and March. The surface flow direction around coral islets and sandbanks varied depending on the location and the stage of the tide. The findings suggest that the current in the channel may be considered to be a small part of the East African Coastal Current that flows northwards, but it is reversed by the Northeast monsoon in the upper layers.
Remotely Operated Vehicles (ROVs) are powerful tools whose use has become common in many aquatic systems, for many purposes, from commercial to research applications. Polar regions, because of ice cover and harsh conditions, remain difficult locations for ROV work. This paper outlines the development of an ROV designed to facilitate exploration and scientific research under sea ice, giving easier access to largely unexplored regions of the seafloor. The ROV SCINI (Submersible Capable of under Ice Navigation and Imaging) was developed at Moss Landing Marine Laboratories and deployed in Antarctica for four field seasons, from 2007 to 2011. Ice provides a convenient deployment platform but commercially available ROVs require a large hole in the ice and much logistic support, which restricts their use in polar regions. Unlike other ROVs, SCINI has a slender torpedo shape (length: 1.4 m, diameter: 15 cm), which allows it to be deployed through a 20 cm hole in the ice. This small hole can be drilled by two people, using a handheld drill. The entire SCINI system and personnel (three or more persons) can fit in one helicopter, thus giving easy and quick access to remote sites. SCINI is a modular vehicle that can easily be modified or serviced in the field. It is also rugged and designed for harsh polar conditions. SCINI is equipped with two video cameras, scaling lasers, and lights. Its maximum depth capability is 300 m. A long baseline acoustic positioning system is used for navigation. SCINI is a highly manoeuvrable vehicle, better suited for flying transects over the seafloor than most ROVs. Engineering tests and scientific surveys were based out of McMurdo Station, Antarctica, and carried out at various sites within a 100 km radius. Knowledge gained from these deployments led to numerous modifications and improvements to the vehicle. This paper provides details on the vehicle's most recent configuration, including mechanical design, electrical design, software, and navigation system. Deployment methods, vehicle behaviour, and results of field testing are described. Four scientific surveys are also briefly described as examples.
Unwanted biological growth on materials immersed in aquatic environments, widely known as biofouling, represents one of the primary obstacles to long-term autonomous deployment of aquatic sensors. Without regular removal, biofouling can disrupt data collected by such sensors. To date, this occurrence has been prevented by the application of biocidal coatings, many of which are harmful to the aquatic environment and which have now been legislatively controlled. The current replacement antifouling materials under development are largely unsuited to sensor technologies as they have been developed with large scale applications in mind, such as those required by the shipping industry. Therefore, a strategy for the development of novel, sustainable, antifouling materials for sensor applications is required. Biomimetics, the use of ideas inspired by nature as a means of developing novel technology, or improving existing technology, offer such a pathway to producing novel antifouling methods. However, many of the current generation of biomimetic antifouling materials have not reached the commercialization stage. In this paper, the potential of biomimetic antifouling materials for application to environmental sensors is discussed. We outline a strategy for the identification and production of novel biomimetic antifouling strategies, and discuss the pitfalls of developing antifouling materials based on biomimetic design.
Aquaculture has developed into a global industry, providing an increasing portion of the world's food supply. However, aquaculture can cause environmentally and socially adverse impacts if ecosystem carrying capacity is exceeded or resource-use conflicts occur between multiple stakeholders. The definition of sustainable aquaculture has evolved into an ecosystem approach that addresses spatial and temporal dimensions of environmental, economic, and social parameters. The development of sustainable marine shellfish aquaculture in the U.S.A. is largely limited by the regulatory, siting and public policy issues that surround the use of coastal waters. This project provided technical support to two Northeast U.S.A. towns (Provincetown and Truro, Massachusetts) in order to identify areas suitable for community aquaculture development areas (ADAs) large enough to contain grow-out sites for use by multiple individual farmers. Mapping efforts incorporated publicly available habitat type data and management boundaries, as well as local traditional knowledge of human use and shellfish habitat, in an iterative Geographic Information System (GIS)-based approach. Combined with sustainable aquaculture site selection criteria, the above data were used to identify a suitable site for a 0.2 km2 (50-acre) subtidal ADA in town waters. Acoustic backscatter data collected with an interferometric sonar system were used to classify habitat within the proposed ADA site, and underwater surveys were conducted at 25 stations to qualitatively assess habitat type and document presence of shellfish and benthic fauna. Qualitative characterization of bottom habitat type using sonar data and dive surveys indicated no submerged aquatic vegetation and a smooth, sandy bottom. The only shellfish encountered during underwater surveys was the surf clam (Spisula solidissima); abundance at all stations was ≤ 1 organism/m2. The unique combination of traditional knowledge, publicly available data, and advanced technology proved to be highly useful for practical, cost-effective site selection for sustainable shellfish aquaculture development areas. Journal of Ocean Technology 2011.
The waters adjacent to the Port au Port Peninsula, in Port au Port Bay, Newfoundland and Labrador, are known to be subject to release of hydrocarbons from natural oil seeps and old abandoned oil wells. An investigation was done to determine whether there were sufficient oil compounds present for planned autonomous underwater vehicle (AUV) test missions to develop adaptive sampling algorithms to delineate oil spills. Fluorometers were used in-situ to measure oil concentrations. Oil-and-water samples were taken at selected waypoints for chemical analysis in the laboratory to validate the sensor measurements and to provide a ground truth. Only one of the fluorometers was found to have a minimum detection level that was capable of sensing the hydrocarbons in the water column. The water sample results indicated hydrocarbon levels up to almost 30 ppm in the east side of the bay, just to the west of Shoal Point, but no detectable levels on the west side of the bay. It was concluded that it would be possible to operate an AUV on a planned fixed mission with a pre-programmed search path and record the levels of signal detected from fluorometers or other sensors. However, it would be difficult to implement an adaptive mission in this case because of the low levels of sensor signals resulting from the low concentrations of hydrocarbon present.
Wave energy and power is accessible on almost any body of water. One of the most widely known floating structures to generate renewable energy from the seas and the ocean is wave energy converter Pelamis. In this study, an attempt was made to simulate the dynamic behavior of Pelamis P2 in the software AQWA under the influence of a nonlinear second-order Stokes wave. Pelamis P2 was simulated in different marine conditions including different water depths, wave heights, periods, and angles to assess its optimal operation. With the results in mind, it can be argued that with an increase in water depth, the intensity of the forces created in the joints decrease. This kind of converter shows better efficiency with lower wave heights, while with a rise in the wave periods, the absorbed energy amounts fall. In the modelling, the best collision angle for the waves is when the Pelamis is in the same direction with the waves. The dynamic behavior of the converter under the effect of irregular waves was surveyed; it shows a better performance under irregular waves compared with regular waves.
The paper presents a general methodology for the reliability assessment of hydrokinetic energy conversion systems harnessing a river current renewable resource. The methodology is applicable to different limit states and performance levels, and it is illustrated with an example using an operating conversion system. The paper also discusses the calibration of a load and resistance factored design (LRFD) procedure for hydrokinetic energy systems for river applications, to achieve minimum target reliability levels or maximum tolerable probabilities of failure, for different limit states and over the service life. The paper presents results for load factors applicable to a combination of applied loads (a permanent load and up to two different live loads).
One of the design challenges faced by naval architects is the accurate prediction of hull resistance characteristics in order to predict precisely the power requirements. Even though a considerable amount of research has been carried out in this area, there remains a degree of uncertainty in the prediction of calm-water resistance of catamaran hull forms. This paper attempts to report on an experimental investigation into a systematic series of slender catamaran hulls. The model hull forms comprise a conventional catamaran along with laterally separated and longitudinally staggered (longitudinal shift between demihulls) demihull (hulls which make up the catamaran) configurations for both symmetrical and asymmetrical hulls. A series of tests on the models were conducted at the Towing Tank of the Indonesia Hydrodynamic Laboratory over a speed range corresponding to Froude number up to 0.7. Experimental results are presented in tabular and graphical forms. The drag characteristics and interference effects are discussed and compared with recently published information. Results presented in this paper offer practical information and considerable promise and it is envisaged that further work will be carried out in order to gain further understanding.
Acoustics have been used in underwater communication and environmental sensing for a century. Sound waves propagate well in water; however, the marine environment poses many challenges to this phenomenon. Designing and deploying an underwater acoustic sensor network has always been a challenge due to the inhomogeneity of the propagation medium. In this paper, a background theory of the underwater sound propagation is provided followed by practical observations and insights into innovative ideas achieved in a lab-scale prototype which assisted in overcoming these challenges. These observations are used to propose a large-scale deployment strategy in the Northwest Atlantic region. Bellhop simulation results provide evidence of the effectiveness of a large-scale system design. This work is focused on finding optimal positioning of the acoustic sensors in the sea while minimizing the multipath effect at the receiver. In addition, the process for precise current speed measurement in a laboratory environment has been explained which elaborates on the practical aspects of a large-scale network deployment in the ocean. The Doppler effect, caused by the motion of the transducers due to wave motion in the sea, is also considered and analyzed for signal processing needs.
Position of the seal haul-out site, Rute Misslauper, where the study was conducted (green dot).
Set-up of camera housing (c), camera housing stand (d), and buoys (b) in relation to the cod pot (a).
Left: view from the side camera. Right: view from the camera above the cod pot.
Seals and fishermen share the role of top consumers in the Baltic Sea, leading to inevitable competition. One aspect of this is that fishermen use fishing gear to catch fish and seals raid these fishing gear. The fisheries lose out in terms of fish catches and also bear the significant costs of damage to the gear. Researchers have been active for some years in developing ‘sealsafe’ fishing gear, which will be unattractive to seals and resistant to attacks. This study investigated the presence of grey seals (Halichoerus grypus) around cod pots and their attempts to take fish from them. Baited and camera-equipped cod pots of three designs including three netting types were set out close to a seal haul-out site east of the island of Gotland in the Baltic Sea. The behaviour of visiting seals filmed with underwater cameras was observed and analysed using a generalized linear model (GLM). As well as the cod pot characteristics, the variables used for modelling included the time of day, whether bait fish were alive or dead, and the quantity of fish in each pot. It was found that the most important cod pot-characteristic for both seal presence and ‘attack behaviour’ was the design of the cod pot. The design which attracted the most seal presence and the most fish-attacking behaviour had loose netting around the upper chamber, in contrast to the other two designs which had tightly stretched mesh. Neither mesh size nor material showed any correlation with seal presence or attack behaviour. It was also found that the most important overall factor for predicting attack behaviour was the time of day. There was individual variation in seal behaviour. The behaviour was categorized into eleven groups, of which ‘investigation’ was the most commonly observed. Most attack behaviours were targeted towards moving fish and no attacks occurred on dead fish. These results could suggest that seals are visiting cod pots because of curiosity and not primarily because of hunger.
The Benthic Rover is a bottom-transecting, autonomous vehicle currently in development at the Monterey Bay Aquarium Research Institute (MBARI), building on the earlier work of Smith and associates at the Scripps Institution of Oceanography. The Rover will be capable of making continuous time-series measurements at abyssal depths up to 6000 m for periods exceeding six months. Core instruments include two respirometer chambers for measuring sediment community oxygen consumption. Three cameras provide close-up images of the sediment surface and a wide-angle view of the Rover's immediate surroundings. A compass and a current meter allow the Rover to move when the current is coming from the desired direction of travel, thus preventing sediment clouds from disturbing the area to be studied. An onboard acoustic modem sends Rover status to surface ships, and receives instructions to change the mission or to terminate the deployment and return to the surface. The vehicle weighs 68 kg in water and moves on two wide tracks with a combined surface contact area of about one square metre to provide good traction while minimizing the disturbance to benthic sediments. At the end of a mission, the vehicle releases a 113 kg steel drop weight to return to the surface. A pair of 10 kWh lithium batteries will power the Rover for extended autonomous deployments. For engineering tests, typically lasting up to a few weeks, much less expensive alkaline battery packs are used. The Rover can also be powered by the Monterey Accelerated Research System (MARS) cable for testing in Monterey Bay at 900 m depth. In addition to power, the MARS cable provides communication capabilities enabling remote control capability and real-time access to Rover data and images, greatly aiding in the development of the autonomous software. Engineering field tests have been performed with the Rover in Monterey Bay (900 m depth), and at Station M, 220 km west of the central California coast (4100 m depth). Rover operations have been observed with the ROVs Ventana and Tiburon, and with the manned submersible DSV Alvin. Knowledge gained from these engineering deployments has resulted in numerous modifications and improvements to the Rover.
This paper reviews deep ocean science operations conducted by the Autonomous Benthic Explorer (ABE), an AUV built and operated by the Woods Hole Oceanographic Institution (WHOI). ABE's operational accomplishments to-date are summarized and a previously unreported survey-the mapping of deepwater corals and their habitats using multibeam sonar and a digital still camera-is discussed. The operations reviewed are representative of the increasing variety of oceanographic surveys conducted by deep-ocean AUVs. As with most AUV deployments, these results involve the use of a single AUV to achieve the prescribed survey tasks. The second part of this paper discusses the extension of the single vehicle operations to the simultaneous operation of multiple AUVs. Based on the technologies and operational procedures developed during single-vehicle operations, we present two potential operating strategies and show the resulting improvements in overall survey productivity.
This paper describes a custom designed electrically powered, fully autonomous 2.73 metre long boat for survey and mapping tasks in locations unsuitable for larger, manned craft. This work was originally inspired by the desire to survey marine terminating calving glaciers in Greenland. The hull has been designed with a bump along the bottom to mount sonar transducers, to push away ice, and to achieve a top speed of around 4 knots. An autonomous control system has been implemented to allow for tele-operation, drive-by-wire, and fully autonomous modes with telemetry data relayed via a radio data link. To extend battery lifetime, a biologically inspired algorithm based on the mammalian endocrine system has been used. Several survey missions have been carried out successfully where the design has proved to be a suitable and low cost platform for survey and ocean mapping work.
Vertical axis turbines are increasingly being utilized to generate power from our oceans. However, due to high levels of dynamic stall and flow interaction effects of the blades, struts, hubs, and shaft, they exhibit complex hydrodynamic flows which need to be fully understood to increase turbine output, service life, and efficiency. Double-Multiple Streamtube (DMS) and Computational Fluid Dynamics (CFD) models were used to numerically investigate the power generated and hydrodynamic properties of these turbines. Three-dimensional (3D) transient CFD simulations were performed using an Unsteady Reynolds Averaged Navier-Stokes (URANS) solver. The DMS model developed incorporated a new correction factor to account for strut drag effects. All simulations were validated against Experimental Fluid Dynamics (EFD) testing of a three-bladed turbine at the Australian Maritime College Circulating Water Channel. The DMS model with a newly developed correction factor for strut drag demonstrated good agreement with the CFD and EFD results for turbine power predictions across the operational tip speed ratio (λ) range. The 3D CFD model of the full turbine geometry including struts, hubs, and shaft also provided good agreement with EFD results for turbine power. The 3D CFD model without struts, hubs, and shaft, and the DMS model without strut correction factors overpredicted turbine performance especially at high λ, as the resistive torque generated by the struts, which reduces power, was not accounted for. All simulation results demonstrate that strut drag, and the associated resistive torque, must be modelled if accurate simulations of vertical axis turbine performance are to be obtained.
In order to allow cod pots to be an alternative to gillnet fisheries, catch has to be increased. In this study we evaluate pot entrance modifications as a means to increase pot catch efficiency. We connect entrance modifications to in-situ cod behavioural events in relation to pot entrances. Pots with entrances lacking funnels allow for a higher proportion of entering cod but also to a larger extent allow cod to exit pots. We show how pots equipped with funnel entrances generate increased catch by preventing escape and, through that, serve as an important factor in regulating cod pot catches. Importantly, we show how entrances equipped with funnels, although inducing a higher proportion of turn behaviour along with increased time in entering, result in a higher net effect in catch than the positive effect in entry if not using funnels. With target species behaviour being a strong regulator of gear catch efficiency, we stress the importance of in-situ observations of specific behavioural components in the fishing gear development process.
Wave reflection, transmission and energy dissipation characteristics of fixed type twin perforated barriers are studied experimentally, under regular and irregular wave conditions. Apart from measuring the reflected and transmitted wave elevations, a systematic effort is made in this study to measure the wave elevations inside the chamber, between two perforated barriers, and the same are analysed to understand their effect on the performance characteristics. The dynamic pressures exerted on the barriers are observed to be functions of wave oscillations inside the chamber. The simultaneous dynamic pressure variation on the seaward side barrier for both seaward-face and leeward-face indicates largest phase difference in dynamic pressure for the chamber width to wave length ratio of 0.25, indicating maximum wave energy dissipation. © 2018, Centre for Applied Ocean Technology, Marine Institute. All rights reserved.
Model tests conducted with a conventional fishing boat model (UBC series model #3) showed that its hull resistance could be reduced by a systematic application of the parabolization concept, a process in which the parallel middle body of the vessel is expanded outward with locally parabolic waterlines. To accomplish this, modifications were made to the hull of a model using add-on retrofits to parabolize the waterlines continuously about the middle body. Residuary resistance values were experimentally obtained and compared with expected predictions based on Michell's integral. These numerical and experimental results suggest that there could be a significant reduction in the ship's Effective Horse Power (EHP) at modest to relatively higher Froude numbers by parabolization of the water lines. The tests show that parabolization might also be used as a retrofit to reduce the EHP of a large class of ships including small craft. An improved hull was designed and tested to combine and validate the results obtained in these tests. An extension of the experimental results to numerical optimization methods suggests that the application of conventional constraints, such as constant beam and constant displacement, may not be appropriate at higher Froude numbers. In addition, the tests showed that the frictional resistance coefficient increased during this process, which could be seen contradicting Froude's hypothesis.
Cod pots are considered seal-safe fishing gear and are proposed as a solution to mitigate the ongoing seal-fisheries conflict in the Baltic Sea. This study examined various factors which could affect the entry and exit behaviour of cod in relation to cod pots. Statistical modelling was used to determine which of these factors most affected the pots’ catch per unit effort (CPUE). Two fishing trials were conducted off the coast of Bornholm, Denmark, using six pot types with different design features, equipped with underwater camera systems to record the behaviour of the cod in relation to the pots. Four pot types were floating pots with one entrance and two were bottom standing with three entrances. Different pot types showed significantly different CPUEs and the pot type was an explanatory factor for entry and exit rates for both trials. In trial 1 artificial light was used for filming and results showed an increase in entry rates during the night time, suggesting that lights attract fish to the pot when the dark surroundings make the effect of the light more noticeable. Exit rates in trial 1 increased with an increasing number of fish in the pot while they decreased with soak time. In trial 2, when no artificial light was used, a saturation effect was found in that the probability of cod entering the pot lessened as the number of cod already in the pot increased. However, the exit rates in trial 2 also decreased with increasing number of fish in the pot. The study offers greater depth to the understanding of CPUE results by examining fish behaviour around the pots and not just the raw catch data. This in turn contributes to the ongoing search for the most favourable pot designs.
Electrified vehicles (EVs), including hybrid electric vehicles (HEVs) and pure electric vehicles (PEVs), have shown substantial improvements of energy efficiency, emission reduction, and possible life-cycle cost saving over conventional vehicles solely powered by internal combustion engines (ICE). Progress on electrification of marine vessels has been made; however, the pace has been impacted by the different operational requirements of each type of vessel, relatively small batch of production, longer or varied lifetime, and complex design optimizations of the vessels’ electric propulsion system and energy storage system (ESS). In this work, the hybrid electric and pure electric propulsion system designs for lobster fishing boats are studied based on in-field acquired operation data. A new integrated marine propulsion system modelling and simulation method and software tools, and a dedicated mobile data acquisition system have been introduced to support the quantitative analyses of energy efficiency, emission reductions, and life-cycle costs of a new or retrofitted fishing boat with hybrid electric and pure electric powertrains, compared with the traditional ICE powered benchmark. Following the automotive industry’s model based design (MBD) approach, modelling and simulation of electrified fishing ships under the acquired operation profile in MATLAB/Simulink have been carried out. Series hybrid electric and pure electric powertrain system designs with powertrain component models and rule-based system control, including properly sized electric ESS with supercapacitor (SC) or battery, have been studied. The total CO2 equivalent or greenhouse gas (GHG) emissions and life-cycle costs of various new, electrified boat propulsion system designs have been quantitatively evaluated against conventional ICE powered boat with both gasoline and diesel engines. The life-cycle costs of the competing powertrain systems include the investment costs, operation/energy-consumption costs, and the replacement costs of key powertrain components over a projected ten-year operation life. Both of the new hybrid electric and battery powered pure electric boat designs showed considerable GHG emissions reduction and favourable lifecycle cost saving. The study presents superior clean propulsion system solutions for lobster fishing boats with quantitative justification and detailed powertrain system and control system designs, forming the foundation for further research and development.
Understanding the relative influences of the thermodynamic forcings and meteorology on the break-up of land-fast sea-ice is important for understanding land-fast ice environments and for broadening our understanding of the factors which control the timing of onset of seasonal break-up. Additionally, model predictions of land-fast ice break-up are of great importance to the shipping industry when the fast ice can seasonally block access to ports, as well as to inhabitants of local communities who depend on a solid winter fast ice cover for coastal travel by snowmobile. In early April 2015, two satellite-linked ice tracking buoys were deployed near the offshore edge of the land-fast ice east of Makkovik, Labrador, and three tracking buoys were deployed on the fast ice east of Nain. The buoys’ recorded movement in late April offshore Makkovik and in early May near Nain marked the precise timing of the onset of the land-fast ice break-up at each buoy deployment location. This study employs a one-dimensional thermodynamic ice model to explore the relative influences of thermodynamic forcing parameters on the ice during the month leading up to the fast ice break-up offshore Makkovik and Nain. The paper focuses in particular on the influences of the regional cloud cover, relative humidity, and wind conditions on the timing of break-up onset through a model sensitivity analysis. The results of the analysis of the relative influences of the thermodynamic forcing components show that the fast ice break-up in both areas was most heavily influenced by the down-welling atmospheric longwave and incoming solar shortwave radiation. The results of the sensitivity analysis reveal that while relatively cloudy conditions during April 2015 most likely delayed the onset of the break-up by two to three days, humid and windy conditions during the month appeared to hasten the onset of break-up by up to two weeks.
Helicopter emergency breathing systems (EBS) have been developed to improve the probability of survival following capsize or sinking. It is recognized that there is a mismatch between the breath-holding ability of helicopter occupants and the time required to escape from a submerged or inverted helicopter. This problem is exacerbated in cold water due to the effects of 'cold shock.' By extending the time that can be spent underwater, EBS improve the chances of making a successful escape and provide protection from the high risk of drowning. To date, only a limited amount of work has been undertaken to investigate the performance of different designs of EBS [see Coleshaw, 2003; Brooks and Tipton, 2001] with particular attention given to deployment times that have not previously been reported. Further, while EBS usage is increasing, there is currently no standard against which performance can be assessed. A technical standard would help to ensure that EBS on the market provide an adequate level of protection from drowning, that minimum performance levels are met and that the health and safety of the user is protected. This paper will therefore describe some of the work undertaken to fill the knowledge gaps relating to EBS performance. Trials of three generic designs of EBS have been undertaken. Measures including emergency deployment time and duration of use have been investigated as well as potential problems associated with helicopter underwater escape. Design issues have been identified with the aim of limiting potential problems during emergency use. The results of this study have been used to develop requirements and test procedures for the proposed EBS technical standard, to be published by the UK Civil Aviation Authority (CAA), for voluntary adoption by industry. The draft technical standard will then be submitted to the European Aviation Safety Agency (EASA) for possible publication as a European Technical Standard Order (ETSO).
The aim of this study was to produce design charts to predict inelastic collapse pressures for thick-walled circular cylinders under uniform external pressure because the existing charts were out of the range for shorter and thicker vessels. Both theoretical and experimental investigations were carried out on 15 stainless steel models, which were tested to destruction and reported for the first time. A theoretical investigation was also carried on other models, tested by previous researchers, to give more points and more credibility to the design chart. The theoretical investigation was based on an analytical method because previous work proved that, in general, it was superior to numerical methods for this particular problem. It was hoped that the details from the current series of models, together with the new design chart, would enable some smaller submarines to descend to the bottom of the Mariana's Trench (11.52 km or 7.16 mi); one of the models collapsed at a pressure of about 1000 bar, which was equivalent to a submarine diving to a depth of about 10 km (6.2 mi).The analytical solution adopted the von Mises buckling analysis via a home produced computer program called MisesNP, which also calculated the Windenburg thinness ratio (λ). By plotting the reciprocal thinness ratio against the plastic knockdown factor (PKD), where the PKD was obtained by dividing the theoretical buckling pressure by the corresponding experimentally obtained buckling pressure for each vessel, a useful design chart was produced.
From the sea surface temperature (SST) record’s origins, voluntary observing ships (VOSs) have been collecting SSTs as part of their ship’s logs, with moored buoys supplementing these for increased accuracy and continuity. National Data Buoy Center (NDBC) buoy’s thermistor has no direct contact with ocean water, providing a potential source of bias. The SSTs were examined for statistical differences between the VOS and buoy data. The 25 NDBC buoys with the most complete record were compared to VOS data for the surrounding waters, with no statistical differences (p = 0.788) found between the two. However, many large (>14 days) gaps and non-physical anomalies were found in the buoy record. Removing the outliers leaves insufficient data for performing climate analyses; most of these buoys require another 10-15 years of uninterrupted data collection for effective use in climate studies.
This paper reviews the constructional details of single-core and three-core AC power submarine cables. The inductance and capacitance electric circuit parameters are then evaluated in terms of the geometry, electromagnetic, and electrostatic (dielectric) properties of the conductors and insulation of the cable. Given the electric circuit parameters, two-port network models are then evaluated which allows the determination of steady state electrical performance characteristics of the cables. The study examines the effect of the cable length on the receiving end (cable output) voltage, active, reactive power and performance indices such as transmission efficiency and voltage regulation.
The aim of SmartBay Galway is the development of a strategically positioned marine research platform, with a reputation for the development of leading-edge technologies for global markets and for the development of innovative solutions to address important environmental issues. The SmartBay project has seen the deployment of a number of environmental sentinel platforms and the integration of existing sensors and information sources into a data and information environment with an innovative human interface with advanced visualization capabilities supporting multidisciplinary users. SmartBay Galway has, at its core, a real time sensor data warehouse that supports multiparameter and multiscale sensor feeds. One of the key goals of the project is to mobilize research skills and expertise based in Ireland in fields such as microelectronics, sensors, advanced materials, and communications involving scientists, technologists, and the corporate sector. The innovative aspects of the project are broad in that a robust open, yet flexible, foundational infrastructure has been demonstrated which can quickly adapt to support new projects, sensors, input data streams, and users, providing numerous benefits to a diverse research community.
Rapid, comprehensive measurements of coastal ocean processes are often difficult to acquire, particularly in shallow water. A novel personal watercraft-based system for rapidly measuring coastal hydrography in shallow waters has been developed, and field-tested, to overcome traditional limitations of hydrographic data collection. The three-person personal watercraft, capable of safely acquiring measurements in water depths < 0.8 m, provides a stable, robust, agile, and inexpensive platform for measuring bathymetry, currents, and comprehensive nearsurface water chemistry. The personal watercraft is outfitted with a bottom tracking acoustic Doppler current profiler; a real-time kinematic differential global positioning system; a handheld temperature and salinity profiling device; a suite of sensors for underway sampling of near-surface water chemistry; and a small five-parameter meteorological station. Typical horizontal resolution of bathymetry and water velocity is O[1 m]. Continuous underway sampling of near-surface water chemistry parameters occurs via a custom designed ram intake and diaphragm pump. Sampling of near-surface water chemistry can be conducted at speeds as high as 20 m/s, allowing for rapid surveys with large spatial coverage. Measurements of near-surface hydrography yield horizontal resolutions of O[1 m]-O[100 m] depending on vessel speed and sampling frequency. Surveys have been conducted in Mobile Bay, Alabama, a nearby river, and a local reservoir; pertinent results from field deployments of this system are discussed and demonstrate the utility and capabilities of this unique measurement platform, particularly the ability to perform nearsynoptic measurements of coastal ocean processes with the express purpose of minimizing tidal bias.
Developing simulation models of tidal, marine and river current devices can be a challenge especially when the diversity of various concepts comes into play. Various design and operational aspects can also create ambiguity on how the critical performance measures are to be interpreted and modelled. This work presents a set of theoretical observations and conceptualized model blocks that can be readily used for simulating a wide range of hydrokinetic energy conversion (HECS) devices. This approach is primarily meant for assessing energy extraction at the front-end of a hydrokinetic device. Relevant default model parameters are given and two case examples are demonstrated.
Accurate numerical models of planing hull motion in waves are required to create a realistic environment for training Fast Rescue Craft (FRC) operators in a real-time simulator. A simulator allows personnel to practice search and rescue and patrol operations in harsh environments without risk. High fidelity models of vessel motions, such as slamming, are necessary for an immersive training environment that will prepare trainees for real world conditions. It is difficult to simulate the motion of FRCs on a simulator because they exhibit strong non-linear motions which cannot be simulated well by linear ship motion theory. In this paper, a non-linear time domain mathematical model has been developed for predicting the vertical motions of a planing hull in head waves. The algorithm for predicting planing motions and forces is based on a twodimensional strip theory that can be run in real-time and fast mode. A computer program has been developed and the numerical model has been validated with the model test data. It was found that the method gave good predictions of heave and pitch motions in semi-planing and planing speed regions. The numerical models developed were tested in an FRC Simulator provided by Virtual Marine Technology Inc. (VMT).
Top-cited authors
Tariq Iqbal
  • Memorial University of Newfoundland
Andrew J Wright
  • Fisheries and Oceans Canada, Dartmouth, Canada
Mark P Simmonds
  • University of Bristol
E.C.M. Parsons
  • University of Exeter
Sarah J Dolman
  • Environmental Investigation Agency