Passage Of Ships Research Articles

Analysis of underwater radiated noise from ships using distributed acoustic sensing technology

Distributed Acoustic Sensing (DAS) technology enables continuous monitoring of acoustic vibrations along fiber optic cables, providing high-resolution spatial and temporal data. This study explores the application of DAS technology for analyzing underwater radiated noise from ships. In November 2021, four days of DAS data were collected using two cables from the Ocean Observatories Initiative Regional Cabled Array, extending offshore central Oregon. Numerous ship passages occurred over these cables, with information available through the Automatic Identification System (AIS). DAS data were collected using two different interrogators on two fibers in each cable, providing an opportunity to investigate the differences in ship noise detected on different fibers within the same cable and across different DAS systems with varying configurations. Preliminary analysis of two large ships shows that their noise is clearly detected in the DAS measurements. By combining these measurements with AIS data, we can accurately locate the receiving channels on the cable. This talk will expand on these observations to perform a comparative analysis of the measurements across different fibers and interrogators. These findings demonstrate the capability of DAS technology in maritime acoustic monitoring and its potential to enhance our understanding of underwater noise pollution.

Possibilities of forming a territorial development zone "Vetluga - Sura". Some directions for the development of water tourism and infrastructure

The article proposes the creation of a territorial development zone "Vetluga-Sura" in the Volga Federal District, the purpose of which should be to increase the economic level of remote areas, improve the standard of living of the population, as well as increase the number of residents both along the banks of the Vetluga and Sura rivers and in the adjacent territories of the region. Within the framework of the territorial development zone, public investments in transport infrastructure are envisaged, including the creation of ship passages on the Vetluga and Sura rivers. In this regard, a wide range of investment projects aimed at the development of the tourism cluster, as well as industry, agriculture and other industries in the region are expected. A significant result of the implementation of the Vetluga-Sura territorial development zone may be the revival of passenger and freight traffic on small rivers in the region. The creation of the Vetluga-Sura territorial development zone is proposed as a pilot project to develop a model of territorial development based on the revival of small rivers and subsequent application in more than 20 other regions.

Galileo's ship and the relativity principle

AbstractIt is widely acknowledged that the Galilean Relativity Principle, according to which the laws of classical systems are the same in all inertial frames in relative motion, has played an important role in the development of modern physics. It is also commonly believed that this principle holds the key to answering why, for example, we do not notice the orbital velocity of the Earth as we go about our day. And yet, I argue in this paper that the precise content of this principle is ambiguous: standard presentations, in both physics and philosophy, fail to distinguish between two principles that are ultimately inequivalent, the “External Galilean Relativity Principle” (EGRP) and the “Internal Galilean Relativity Principle” (IGRP). I demonstrate that EGRP and IGRP play distinct roles in physics practice (e.g., EGRP is connected to the concept of Galilean invariance, but IGRP is not) and that many classical systems that satisfy IGRP fail to satisfy EGRP. I further show that the Relativity Principle famously discussed by Einstein in 1905—which is not restricted to classical systems—also leads to two inequivalent principles, an external one analogous to EGRP, and an internal one analogous to IGRP. I conclude by highlighting that the phenomenon originally captured by Galileo's famous ship passage is much more general than contemporary discussions in the philosophy of symmetries suggest.

Modeling and Solution Algorithm for Green Lock Scheduling Problem on Inland Waterways

Inland navigation serves as a vital component of transportation, boasting benefits such as ample capacity and minimal energy consumption. However, it also poses challenges related to achieving navigation efficiency and environmental friendliness. Locks, which are essential for inland waterways, often cause ship passage bottlenecks. This paper focuses on a green lock scheduling problem (GLSP), aiming to minimize fuel emissions and maximize navigation efficiency. Considering the realistic constraints, a mixed-integer linear programming model and a large neighborhood search solution algorithm are proposed. From a job shop scheduling perspective, the problem is decomposed into three main components: ship-lockage assignment, ship placement subproblem, and lockage scheduling subproblem coupled with ship speed optimization. A large neighborhood search algorithm based on a decomposition framework (LNSDF) is proposed to tackle the GLSP. In this, the complex lockage scheduling problem is addressed efficiently by mapping it to a network planning problem and applying the critical path method. Numerical experiments substantiate the effectiveness of our proposed model and a heuristic approach was used in solving the GLSPs. In the sensitivity analysis, under three different objective weight assignments, the resulting solutions achieved average effective ship fuel savings of 4.51%, 8.86%, and 2.46%, respectively. This indicates that our green lock scheduling problem considering ship speed optimization can enhance ship passage efficiency while reducing carbon emissions.

The anchorage in cramped travel conditions

It is known that the safety of the anchorage is largely determined by the correct choice of the anchorage location, the depth and type of soil, the dimensions of the water area, protection from wind exposure, the presence of currents in the anchorage. Parking on sea raids in terms of the limited water area does not pose any special problems. In river conditions, the raids are located in close proximity to the ship's passage and are limited in width. Therefore, the question of the width of the strip occupied by the anchored vessel is important. Vessels on the river usually stand on the bow anchor against the current, but quite often, with strong crosswinds, it is necessary to give up the stern anchor in order to reduce the width of the lane occupied by the vessel and not interfere with the movement of passing vessels. The paper presents studies of safe conditions for anchoring ships in river conditions with wind in a limited-sized water area at different flow speeds. Calculated dependences are obtained for determining the transverse size of the water area occupied by a vessel standing at the bow anchor, bow and stern anchors with respect to the axis of the ship's course, depending on the speed of the current, wind speeds and direction.

Potential benefits of climate change on navigation in the northern sea route by 2050

Climate change has been inducing a continuous increase in temperatures within the Arctic region, consequently leading to an escalation in the rates of Arctic ice depletion. These changes have profound implications for navigation along the Arctic Northern Sea Route (NSR). However, access to the NSR is constrained to specific temporal intervals when the sea ice thickness reaches a threshold that permits safe passage of ships. This research employs climate change model simulations and the Polar Operational Limit Assessment Risk Indexing System framework to investigate the navigational feasibility of diverse ship types along NSR during the calendar years 2030, 2040, and 2050, under SSP2-4.5 and SSP5-8.5 scenarios. Different ship categories were analyzed within the context of these two scenarios. Results indicate considerable variation in the navigability of different ship categories across different scenarios and years. In general, polar ships demonstrate a higher navigational potential throughout most of the year, while pleasure crafts are constrained to specific periods. These findings bear significant implications for the future of shipping along the NSR. As Arctic ice continues to melt, NSR is anticipated to become more accessible to ships, albeit with navigational availability remaining contingent on the ship category and seasonal considerations.

Field study on endogenous perfluoroalkyl acid release and their spatiotemporal distribution processes induced by inland navigation

Dense populations and industries in regions with developed inland waterways have caused the significant discharge of perfluoroalkyl acids (PFAAs) into surrounding waterways. Despite being the dominant energy input in the waterways, the impact of ship navigation on endogenous PFAA release is unclear. In this study, a field experiment was carried out in the Wangyu River (Taihu Basin, China) to investigate the spatiotemporal distribution processes of PFAAs in the water column after passage of ships with different tonnages, speeds, and draughts. The results showed that the PFAA contents did not decrease continuously with time but increased with a lag after the passing ship triggered a transient massive dissolution of PFAAs into the overlying water. In addition, PFAA contents in suspended particulate matter (SPM) exhibited a fluctuating downward trends after their peak at the moment of ship passage. Vertically, the PFAA concentrations among the layers of overlying water were relatively homogeneous, whereas SPM exhibited substantial heterogeneity in its distribution and adsorption of PFAAs. Moreover, the differences in jet scouring velocity (u), disturbance duration (t), and draught (h) of ships resulted in large variability in PFAA contents in the water column. Variance partitioning analysis further quantified the effects of u, t, and h on total PFAAs in the water column, with individual contributions of 53 %, 12 %, and 6 %, respectively. Furthermore, the release of endogenous PFAAs induced by ship passage involved rapid and slow processes, the former determining the overall PFAA release and the latter affecting PFAA concentration recovery in the water column. The findings provide in-situ observational data on spatiotemporal variations of PFAAs in multiphase media following ship passage, enhancing our understanding of endogenous pollution in inland waterways.

The mental image of the United States of America among the Jordanian public after the outbreak of the Gaza Wa

This study aims to explore the mental image of the United States of America among the Jordanian public after the outbreak of the events of October 7, 2023, which led to the eruption of a war between Hamas and Israel. This war resulted in the deaths, injuries, and disappearances of tens of thousands of victims. The war extended to neighboring countries, where Hezbollah from southern Lebanon, some Islamic organizations supporting Iran in Iraq and Syria, and the Houthi Ansar Allah group from Yemen participated. The Houthis prevented the passage of American, Israeli, and British ships, declaring that they did so in solidarity with Hamas, which governs the Gaza Strip. This study is descriptive in nature, and within its general framework, the survey method was adopted. An electronic survey tool was used to collect information about the study sample, with 370 individuals considered leaders of public opinion in Jordan. The study revealed that the image of the United States of America is negative among the Jordanian public, as political and popular leaders organized sit-ins and protests in front of the US Embassy in Amman in protest against its supportive stance toward Israel. The study sample considered that the United States of America strongly supports Israel, providing it with money and weapons, and considers it the main supporter of this country in the Middle East and the world.

“River Ice above and Below the City Has Passed”: Development of Waterways in the Neva Region at the Beginning of the Great Northern War

The paper is devoted to the problems of obtaining, the “mechanism” for transferring, generalizing and using knowledge about the natural and climatic features of the lands conquered from Sweden during the Great Northern War (1700—1721) and became part of the Ingermanland province. The beginning of the development of waterways in the Neva region is associated with military actions, when the Russian command needed to organize the transportation of people and cargo. The main information about waterways came from local residents — landowners, traders and peasants. Shipyards were founded on the rivers flowing into Lake Ladoga, where the first ships of the Baltic Fleet were built. The development of waterways included not only measuring river depths, clarifying fairways, but also observing the weather. Analysis of reports from Shlisselburg commandant Poroshin to Menshikov allowed to establish that his duties included ensuring the safe passage of ships past the fortress, as well as immediately informing the governor and the St Petersburg chief commandant about changes in weather conditions on Lake Ladoga. During the Great Northern War, topographical study of the Neva region was carried out simultaneously with its economic development. By the end of the reign of Peter I, the Neva turned into the main transport artery of St Petersburg, and a system to inform the city residents about the time of opening and freezing of the river was established.

Maximizing Efficiency in the Suez Canal: A New Approach to Evaluate the Impact of Optimal Time-Varying Tolls on Ship Arrival Times

In the existing literature, an optimal time-varying toll scheme has been proposed for the Suez Canal to address the inefficiency of numerous ships queuing and waiting at the anchorage area to enter the canal. The primary objective of this tolling strategy is to alleviate the significant issue of ships queuing at the canal’s anchorage area. This stands in contrast to the current tolling system employed by the Suez Canal, which primarily aims to recover the management and operational costs associated with ship passage through the canal. However, the existing literature has yet to explore how the arrival times of ships at the anchorage area will change after implementing the optimal time-varying toll scheme. The goal is to ensure that the equilibrium cost of each tolled ship does not result in losses and achieve maximum efficiency in eliminating queueing at the anchorage area. To address this gap, this paper adopts the principle of cost equilibrium conservation and utilizes the Point-Slope Form to derive two mathematical formulas representing all ships’ post-toll arrival times at the anchorage area of the Suez Canal. These formulas are specifically derived for two categories of tolled ships: those that enter the canal earlier than the latest entry time regulated by the canal authorities and those that enter later. The derived formulas are concise and comparative, strengthening the theoretical underpinnings of the current pricing model for a queuing canal. Furthermore, they serve as valuable references for canal authorities in devising pertinent measures, such as organizing the scheduling of canal pilots, to facilitate the implementation of the optimal time-varying toll scheme.

Improvement of the mathematical model of the navigation area for the optimal ship passage route

Planning the optimal route of a vessel passage is a key problem in the design of traffic planning and navigation systems. This problem consists in the need to determine the trajectory from the initial point to the final point, which ensures the absence of collisions with obstacles. When solving this problem, it is also necessary to take into account the dynamics of the vessel, the uncertainty and non-stationarity of the water environment, the time to calculate the path and the physical feasibility of the trajectory. The planning task is traditionally formulated as the task of optimizing the state of the current position of the vessel relative to the target position. Most often, this problem is solved in the configuration space, which consists of a set of obstacles, kinematic and dynamic constraints, and a set of points in the swimming areas. Planning methods are divided into global and local. Global methods build a route based on a known map, while local methods adjust the path when obstacles are detected. However, at the moment, mathematical models of the navigation area only partially take into account the uncertainties of the zones in which the vessel operates. This determines the planning of local trajectories within a specific swimming area using a simple straight-line algorithm. Since in the process of planning the transition from «berth» to «berth» in order to ensure the navigational safety of the ship, it is necessary to use all available information to compile the most detailed imaginary model of the ship's transition before the start of each voyage. In order to solve this task, this paper proves that in the process of building the optimal route, it is necessary to conduct a full analysis of all stages of the passage of the vessel, which increases the optimality of the planned passage route. The mathematical model of the navigation area for the optimal route of the ship's passage has been improved, in which the mathematical apparatus of fuzzy sets is applied

Risk Approach Based on the FRAM Model for Vessel Traffic Management

Abstract This study analyzes the risks in ship traffic services management using the functional resonance analysis method (FRAM), a novel approach that focuses on identifying interactions leading to performance variability rather than errors. The research area is the Turkish Straits vessel traffic service management (VTSM) region, known for frequent risky ship passages. The goal is to ensure safe VTSM, minimize the negative impacts on people, goods, and the environment. The daily routine functions of the VTSM, determined through consultations with vessel traffic operators (VTOs), are explained by following FRAM analysis principles. Qualitative methods, aligned with expert opinions, are used to examine potential performance variabilities and hazard factors. The resulting risk situation for each function is categorized by criticality on a color-coded scale. Solution proposals are provided to manage critical function variability, enhancing the VTSM system's responsiveness and adaptability.

Brash ice macroporosity and piece size distribution in ship channels

Merchant vessels' performance on brash ice plays an important role in navigation in fast ice conditions in Northern Baltic ports. Among many parameters, the piece size distribution and macroporosity of the brash ice influence the accuracy of the model simulations of ship performance in brash ice. These properties also govern the brash ice accumulation and consolidation in ship channels. The current work presents analyses of macroporosity and piece size distribution from three full-scale brash ice channels investigated during winters 2020–21 and 2021–22. The results provide insights into brash ice macroporosity and piece size distribution. Smaller brash ice pieces exhibited higher porosity. On each measured cross-section, the average macroporosity ranged from 1.4% to 23%, with standard deviations of 3.8% and 16%, respectively. Porosity variations were observed in relation to equivalent brash ice thickness, the number of ship passages, and cumulative freezing air temperatures. Total porosity and the channel's brash ice porosity initially increased with breaking events and then stabilized at approximately 23% and 30%, respectively, after 9 passages. In contrast, side ridge porosity increased initially (up to 23%) and subsequently decreased. The initial total, brash ice and side ridge maximal porosities after the breaking event were estimated equal to 25%, 35% and 30%, respectively. The first two channels, which were navigated a total of 9 and 10 times, had an average degree of brash ice consolidation equal to 0.84 and 0.76, and an average degree of side ridge consolidation equal to 1.1 and 1.0, respectively. The third channel, characterized by frequent navigation, exhibited a consolidation degree of 0.82 for brash ice and 1.35 in the side ridges. The average vertical piece size across all cross-sections ranged from 0.28 m to 0.52 m with standard deviations of 0.16 m and 0.25 m. The average horizontal piece size ranged from 0.33 m to 0.4 m with standard deviations between 0.2 m and 0.34 m. The horizontal piece size distribution of brash ice was best described by the probability density function of a three-parameter lognormal distribution.

The assessment of the possibility of achieving guaranteed dimensions of the ship's passage to create conditions for the development of river tourism on the Lower Vyatka

The establishment and maintenance of guaranteed dimensions of the ship's passage on the waterway requires an integrated approach. First of all, this is due to the influence of the level regime of the water body on the increase in the depth of the watercourse, taking into account the possible setting of the water level. Navigation conditions of the river Vyatka in the lower reaches largely depend on the influence of the support of the Kuibyshev reservoir. The authors substantiated the areas of support within the boundaries of the investigated area from the Vyatskiye Polyany hydraulic bridge to the Sokolyi Gory hydraulic bridge, conducted studies on the calculation of water level setting during the development of shipping slots. As a result, it was revealed that it is possible to establish guaranteed dimensions on the Lower Vyatka in a section from the mouth of the river to 40 km, including the city of Mamadysh. In the upper section of the river, the hydraulic features of it do not provide a reasonable opportunity to establish the specified dimensions of the path.

Analysis of methods of managing the environmental safety of the navigation passage of ships of maritime transport

The requirements of the MARPOL international convention on ensuring the environmental performance of marine diesel engines in relation to the emission of sulfur oxides, as well as marine fuels during navigation passages of sea transport vessels in special ecological areas, are given. The use of scrubber cleaning of exhaust gases and the use of fuel mixtures, which include biodiesel fuel, are considered as methods that meet these requirements. The research was carried out on ships of the Bulker Carrier class with deadweight of 63,246 tons during the navigation transition between the ports of Northern Europe. One of the vessels used scrubber cleaning of exhaust gases as a method of environmental safety management. The other is the use of fuel mixtures, which include biodiesel fuel. Both vessels are equipped with a 5S60ME-C8.2 MAN-Diesel&Turbo marine diesel engine as the main engine, and three 6EY18ALW Yanmar diesel engines as auxiliary engines. The ratio of sulfur oxides to carbon oxides – SO2/CO2 – was chosen as an indicator for evaluating the effectiveness of environmental safety management methods. This value was monitored and regulated by an automatic monitoring system. It was found that both methods meet the requirements of the MARPOL convention, namely, they will support the SO2/CO2 ratio in the range of 2.29–4.17 (when in special environmental control zones) and in the range of 6.46–20.83 (when in outside the zone of special environmental control). The use of environmental safety management methods increases energy costs for ensuring this process. When using exhaust gas scrubbing, additional power losses reach 237–278 kW. In the case of using a fuel mixture that includes biodiesel fuel, power losses amount to 18–20 kW. It has been experimentally confirmed that the use of a fuel mixture that includes biodiesel fuel is characterized by a lower level of environmental sustainability. At the same time, compared to the use of scrubber cleaning of exhaust gases, this method requires less energy consumption and is also characterized by simpler additional equipment. In this regard (and also taking into account that all the requirements of Annex VI MARPOL are provided), it is recommended as the main one to ensure the environmental safety of navigation passages of sea transport vessels.

Measurement report: Inland ship emissions and their contribution to NOx and ultrafine particle concentrations at the Rhine

Abstract. Emission plumes of around 4700 ship passages were detected between March 2021 and June 2022 in the Upper Rhine Valley in Worms, Germany. In combination with ship-related data recorded via the automatic identification system (AIS), the plume composition of individuals ships was analyzed, and it was possible to quantify their contribution to the overall emission load. To obtain an integral picture of inland ship emissions, nitrogen oxide (NOx = NO + NO2) and carbon dioxide (CO2) measurements in the gas phase were combined with detailed particle-phase measurements including particle number concentration (PNC), particle size distribution (PSD) from 5 nm to 10 µm, particulate matter (PM1 and PM2.5), ultrafine particle fraction (UFP, diameter < 100 nm) and aerosol black carbon (BC). One measuring station was located inside a bridge directly above the navigation channel and was especially helpful in deriving emission factors under real-world driving conditions for the fleet on the Upper Rhine. The other station was situated on a riverbank at about 40 m distance to the shipping lane and was thus representative of the exposure of people working or living close to the Rhine. Inland ships contributed 1.2 µg m−3 or 7 % on average to the local nitrogen dioxide (NO2) concentration at the bridge above the shipping lane. NOx concentrations were increased by 10.5 µg m−3 (50 %), PNC by 800 cm−3 (10 %), PM1 by 0.4 µg m−3 (4 %) and BC by 0.15 µg m−3 (15 %). On the riverbank a NOx increase of 1.6 µg m−3 (8 %) and an NO2 increase of 0.4 µg m−3 (3 %) were observed. More than 75 % of emitted particles were found in the UFP range with a geometric mean particle diameter of 52±23 nm. Calculated emission factors (25–75 percentiles) were 26–44 g kg−1 of fuel for NOx, 1.9–3.2 g kg−1 for NO2, 0.3–0.7 g kg−1 for BC, 0.9–2.3 g kg−1 for PM1 and (1–3) × 1015 kg−1 for PNC, with a large variability observed from ship to ship. Relating these values to ship-specific parameters revealed the importance of engine characteristics, i.e., vessels using old motors with low revolutions per minute (rpm) caused comparably high emission factors for both NOx and PNC. A comparison with emission regulation limits set by the Central Commission for the Navigation of the Rhine (CCNR) and the European Union (EU) showed that – within the uncertainty of our calculation method – mean energy-dependent emission factors under real-driving conditions were slightly exceeding those under controlled laboratory conditions. The results from this study underline the importance of long-term measurements with high temporal resolution to reliably estimate the contribution of inland shipping to air pollution in cities along heavy traffic waterways and to monitor a potential future emission reduction when modernizing the fleet.

Effects of anthropogenic noise and natural soundscape on larval fish behavior in four estuarine species.

The larval and post-larval forms of many marine organisms, such as oysters, crabs, lobster, coral, and fish, utilize ambient acoustic cues to orient, settle, or metamorphose. In this study, the effect of anthropogenic and ambient sounds on the orientation behavior of four larval estuarine fishes was examined in a controlled, laboratory experiment. Pre-settlement size red drum Sciaenops ocellatus, southern flounder Paralichthys lethostigma, spotted seatrout Cynoscion nebulosus, and Florida blenny Chasmodes saburrae larvae were exposed to four sound treatments-control, estuarine soundscape, seismic airguns, and large-ship passage-in a linear acoustic chamber. Initial significant (p < 0.05) avoidance of airguns was observed in three of the four species (all but the Florida blenny), but habituation to this sound occurred as the experiment progressed. All species avoided ship passage sounds; however, the avoidance behavior was not significant. Interestingly, none of the species studied were significantly attracted to the acoustic cues alone of the estuarine soundscape; in fact, three of the four species spent less time near the speaker when it was broadcast. These results suggest that larval fish can potentially habituate to anthropogenic noise relatively quickly (<10 min). Understanding how sounds affect larval behavior is necessary because successful recruitment ultimately affects a population's success.

A multi-objective optimisation strategy for ice navigation under ship safety-following scenarios

Shipping activities in the Northern Sea Route (NSR) are increasing. However, due to the complex sea ice conditions, ships still need assistance of icebreakers when sailing through most Arctic waters. Icebreaker escort operations are important to ensure the safe passage of ships through ice-covered waters, but the speed of following ships will be limited, thus creating challenges for NSR sailing economics and emission reduction issues. Optimizing the sailing speed of following ships can reduce NSR ship emissions and improve navigation economy while safeguarding their sailing safety. In this paper, a green, economical and safe optimization approach under ship-following navigation has been developed by drawing on similarities with the car-following phenomenon. Then, three ship-following scenarios are designed for simulating the actual ice navigation conditions. Finally, a cost-eco-efficiency multi-objective optimisation model for ice navigation is established, and the performance of the proposed model is demonstrated by the navigation case of “Tian You”. The results show that the proposed model can effectively reduce navigation costs and control navigation emissions while ensuring navigation safety. This study also demonstrates that there is still room for a 20% improvement in the optimised speed and a 4.8% reduction in the ship-following distance compared to the actual situation.

Observations of Snow–Slush–Snow Ice Transformation and Properties of Brash Ice in Ship Channels

The thickness and properties of brash ice are usually compared with the properties of the surrounding level ice. The differences between these ice types are important to understand since the consolidated brash ice layer is typically assumed to have the same properties as level ice. Therefore, significant effort in the measurement campaign during the winters of 2020–2021, 2021–2022, and 2023 was made to develop a better understanding of the full-scale brash ice channel development. The channels were located near the shore in the Bay of Bothnia, Luleå, Sweden. The main parameters investigated were the snow, slush, and total ice thicknesses, including ice formed from freezing water and from freezing slush as well as the ice microstructure and strength. To our knowledge, this is the first paper to report the influence of snow in brash ice channels. It was observed that a significant amount of snow covered the brash ice channels between the ship passages. After each ship passage, the snow was submerged and formed slush-filled voids, which thereafter transformed into snow ice (SI) clusters frozen together with columnar ice. The SI content in the brash ice and side ridges was estimated from image analyses. The analyses showed that the snow ice content was 73% in level ice in the vicinity of the ship channel, 58% in the side ridges of the channel, and 21% in the middle of the test channel, whereas in the main channel, the SI contents were 54%, 43%, and 41% in each location, respectively.

Decomposition of the induced magnetism degaussing problem for fast determination of currents in demagnetization coils wrapped outside an object under arbitrary external field conditions

Safe passage of ships in the presence of sea mines can be ensured by limiting or reducing the ship’s magnetic footprint. For vessels with plastic hulls, the main component that requires magnetic damping is the engine. Demagnetization of such an object can be achieved by wrapping it with coils and setting the direct current appropriately. For each specific geographic location, the currents in the coils can be determined iteratively from measurements of the magnetic signature in the cardinal directions. In this paper the magnetic signatures are calculated using decomposition-based approach for each coil and each component of the external field separately. Hence the overall magnetic signature of the object can be reproduced in arbitrary external magnetic field (i.e. anywhere on the Earth). Knowing the influence of each coil, it is possible to formulate the optimization task (signature minimization) and determine the currents. The presented method is verified in FEM software with the use of engine models of both symmetrical and asymmetrical shapes. Since the determination of the currents takes place as a result of solving the optimization problem, the effectiveness of obtaining the results, the speed of convergence and the dependence on initial conditions is under investigation. The effect of the model mesh size on the quality of object signature reduction is also analyzed. The developed method can be used for a real object. In that case acquiring the data then requires the measurements of the object placed inside the Helmholtz coils.