Underwater Hull Research Articles

Australia II: A Case Study in Engineering Ethics

Australia II became the first foreign yacht to win the America's Cup in 1983. The boat had a revolutionary wing keel and a better underwater hull form. In official documents, Ben Lexcen is credited with the design. He is also listed as the sole inventor of the wing keel in a patent application submitted on February 5, 1982. However, as reported in New York Times, Sydney Morning Herald, and Professional Boatbuilder, the wing keel was in fact designed by engineer Peter van Oossanen at the Netherlands Ship Model Basin in Wageningen, assisted by Dr. Joop Slooff at the National Aerospace Laboratory in Amsterdam. Based on telexes, letters, drawings, and other documents preserved in his personal archive, this paper presents van Oossanen’s account of how the revolutionary wing keel was designed. This is followed by an ethical analysis by Martin Peterson, in which he applies the American NSPE and Dutch KIVI codes of ethics to the information provided by van Oossanen. The NSPE and KIVI codes give conflicting advice about the case, and it is not obvious which document is most relevant. This impasse is resolved by applying a method of applied ethics in which similarity-based reasoning is extended to cases that are not fully similar. The key idea, presented in Peterson’s book The Ethics of Technology (Peterson, The ethics of technology: A geometric analysis of five moral principles, Oxford University Press, 2017), is to use moral paradigm cases as reference points for constructing a “moral map”.

Design of a new composite underwater hull cleaning robot

In light of the issues associated with marine organisms adhering to hull surfaces during sea transportation, leading to additional fuel consumption and hull damage, this paper proposes a novel design for an underwater hull cleaning robot. Building upon existing technology, the robot integrates traditional mechanical cleaning and cavitation jet cleaning methods, enhancing both approaches. It can first mechanically clean most of the attachments of the hull, and then deeply clean the remaining residues of the cavitation jet, so as to achieve efficient and non-destructive comprehensive cleaning of the hull surface, thereby reducing the ocean transportation cost. We used SolidWorks to conduct modeling and solid simulation experiments, and fluent to conduct fluid simulation experiments. The experimental results show that the robot can meet the cleaning needs of offshore platforms.

Overview of Underwater Robots for Hull Cleaning

At present, the cleaning of the hull surface in China is carried out in the dock, and the cleaning equipment that can be successfully used in underwater operations still needs the assistance of divers in the water, which is high cost and low efficiency. This paper introduces the current situation of hull cleaning robots at home and abroad, as well as the advantages and disadvantages of related technologies, such as dock cleaning technology, underwater cleaning technology, etc., and analyzes the development trend of underwater hull cleaning equipment in the future, providing a theoretical basis for the development of hull cleaning equipment. Underwater cleaning robots have been a rapidly developing research and application field in recent years. Its main goal is to perform cleaning, maintenance, and monitoring tasks in an underwater environment by automated or semi-automated means. Such robots are used in a wide variety of application scenarios, including but not limited to oilfield maintenance, marine debris removal, reservoir and pond management, and ship maintenance study design: Underwater cleaning robots are capable of working long hours in harsh environments and their programmability and versatility enable them to perform a variety of complex tasks. In addition, with the development of advanced technologies such as the Internet of Things (IoT), artificial intelligence (AI), and deep learning, the level of intelligence of these robots is also gradually improving. With global industrialization and population growth, the problem of underwater environmental pollution is becoming more and more serious. Traditional underwater cleanup methods often rely on human labor, which is not only inefficient but also can pose a safety risk to workers. Therefore, automation technology has great potential and value in this field. To sum up, underwater cleaning robot is a multidisciplinary field, involving mechanical engineering, electronic engineering, computer science, and environmental science. It not only contributes to solving current pressing environmental problems but also provides new research and application opportunities in related fields.

Toxic effects of the wastewater produced by underwater hull cleaning equipment on the copepod Tigriopus japonicus

Unmanaged disposal of wastewater produced by underwater hull cleaning equipment (WHCE) is suspected to induce toxic effects to marine organisms because wastewater contains several anti-fouling compounds. To investigate the effects of WHCE on marine copepod, we examined the toxicity on life parameters (e.g. mortality, development, and fecundity) and gene expression changes of Tigriopus japonicus as model organism. Significant mortality and developmental time changes were observed in response to wastewater. No significant differences in fecundity were observed. Transcriptional profiling with differentially expressed genes from WHCE exposed T. japonicus showed WHCE may induce genotoxicity associated genes and pathways. In addition, potentially neurotoxic effects were evident following exposure to WHCE. The findings suggest that wastewater released during hull cleaning should be managed to reduce physiological and molecular deleterious effects in marine organisms.

Insight into the underwater implosion mechanisms of thin-walled metallic cylindrical shells

Underwater hollow structures are prone to implosion due to high hydrostatic pressure and structural imperfections. The implosion deformation patterns and induced shock wave impulses are quite involved, and the underlying mechanisms are still not clear. This paper presents an investigation of the implosion mechanisms of metallic cylindrical tubes. The finite element model is first established and validated by the existing experimental results. Numerical simulations are then performed for the aluminum alloy (6061-T6) cylindrical tubes with different length diameter and wall thickness. The deformation features, as well as the induced implosion shock wave characteristics, are analyzed, and the boundaries for the switch of deformation modes are derived. Furthermore, a comparison between the implosion of the cavity and that of the cylindrical shells is implemented. Results show that with the variation of geometrical dimensions, three deformation modes are developed for the cylindrical shells. The implosion shock wave pressure is non-uniformly distributed in the nearby fluid field, and the higher peak is generated in the area around the valleys of the deformed shells. The finding of this work can help understand the implosion mechanics and facilitate the design of underwater hull structures.

Research on Underwater Hull Inspection Robot Based on Fixed Depth Control

Research on Underwater Hull Inspection Robot Based on Fixed Depth Control

Modal analysis of underwater hull cleaning robot considering environmental interaction

Cleaning ship's fouling can increase the speed up to 95–98% of the original value, decrease fuel costs, increase the ship's maneuverability, and reduce impeller damage by reducing cavitation. In this paper, the dynamic behavior of an underwater cleaning brush system is investigated using modal analysis while the brushing robot is in contact with an underwater ship's hull. The environmental interaction forces on the rotating filaments are considered, resulting from rotating inertia, hydrodynamic drags, and surface contact with external substances such as twisted algae and sediments with different hardness. A prototype robot is designed and built to test and valid the presented theory. Vibrational interaction forces and bending moments of the rotating brush system are investigated by acceleration sensor ADXL345, Arduino UNO and MATLAB software, and compared with the real experimental data. The experimental results demonstrated the theory which are essential to design a hull cleaning robot's suspension system and increase the surface cleaning quality without damaging the ship's hull and antifouling coating.

Optimization of Maintenance Schedule for Containerships Sailing in the Adriatic Sea

Biofouling attaches to immersed surfaces in between hull cleanings. Due to high speeds and relatively short port times, biofilm often attaches to the immersed surfaces of containerships. In most cases, this type of fouling is not given much importance since it is assumed that it will not cause any fouling penalties. In this paper, the fouling penalties related to fouling with biofilm on the example of the Post Panamax and Post Panamax Plus containership fleets sailing in the Adriatic Sea are assessed. In addition, the investigation is performed for real environmental conditions that a containership can encounter on a sailing route passing through the Adriatic Sea. Thus, the impact of waves and wind is taken into account based on mean values of significant wave height and wind speed for containerships sailing at the design speed along the analyzed route. The procedure for the determination of the detrimental effects of biofilm on the increase in fuel consumption and carbon dioxide emissions is given. Further, the proposed procedure includes the determination of calm water resistance by the Holtrop and Mennen method, the added resistance in waves by Liu and Papanikolaou’s method, spectral analysis using the Tabain’s spectrum for the Adriatic Sea, the wind resistance by the Blendermann method, and added resistance due to biofouling using the Granville method. Thereafter, a time-dependent biofouling growth model proposed by Uzun et al. is incorporated, and the adequate timing for underwater hull cleaning is determined for several hull cleaning costs. The obtained results demonstrate that, from an environmental point of view, proactive hull cleaning should be applied, while, from an economic perspective, optimal timing for underwater hull cleaning is recommended.

The sailing performance of ancient Polynesian canoes and the early settlement of East Polynesia

ABSTRACTScholarly estimates and opinions of the sailing performance of ancient Pacific canoes vary widely. This paper measures performance by testing real sails in a wind tunnel and hulls in a towing tank. The sails were three East Polynesian Oceanic spritsails of late eighteenth century type, held by the British Museum, collected from New Zealand, Tahiti and Hawaii/Marquesas, which conform to the first historical records. Also tested was a hypothetical generic ancestral sail, and the Māori sail was tested in different ways to accommodate different views. Tests of hull form found that upwind sailing performance improved as underwater hull profile changed from U‐shape to V‐shape and some archaeological hulls can be assigned to this scale. Velocity prediction programs (VPPs) were calculated for a range of different canoes and simulated voyages by the fourteenth century AD archaeological canoe (waka) found at Anaweka, New Zealand retraced real voyages made by the experimental Polynesian replica canoe Hōkūle'a between 1980 and 2000, in the same recorded weather. Both canoes could average speeds of up to four knots and sail upwind at 75° to the true wind angle (TWA), as proposed by Lewis and Finney. The paper identifies a package of technological innovations involved in the settlement of East Polynesia following the “long pause” in Pacific settlement in West Polynesia. Two innovations previously suggested by linguistics were the Oceanic spritsail and the double canoe, and a third was the development of complex composite planked hulls and V‐shaped underwater hull forms. East Polynesian canoes were capable of two‐way voyaging and some migrations were planned, as in the case of New Zealand.

DEVELOPMENT OF MODEL-DRIVEN DECISION SUPPORT SYSTEM TO SCHEDULE UNDERWATER HULL CLEANING

Maritime industries are constantly searching for a method to enhance ship efficiency, with increasing concern about the environmental impact and rising fuel prices. Marine biofouling is one of the factors that increase ship fuel consumption. However, removing the fouling of the ship requires effort for hull maintenance. Due to the trade-off between conducting maintenance and performance degradation, this study presents the development of a Model-Driven Decision Support System (MD-DSS) to predict the optimum time for underwater hull cleaning for biofouling management. Five stages (sub-models) are employed to develop a DSS, namely: ship resistance estimation, estimation of additional resistance due to biofouling, an iterative-based method for determining the best time to conduct the hull cleaning, and an analysis report. The implemented algorithm was validated by comparing its result with a manually scheduled maintenance date. The DSS is able to determine the best time (date) for maintenance in all given scenarios. By giving two scenarios of different maintenance costs and different fuel prices, the optimisation results produce the same number of maintenances. Within 60 months, four to five hull cleanings are required. It is also found that when the optimal number of maintenances is known, then increasing this number will not have any impact on reducing the hull cleaning costs because the reduction in fouling does not significantly reduce the costs incurred for maintenance. During several trials of the DSS, it is shown that the system can generate maintenance schedules for different time intervals of ship operation within an acceptable time. It takes approximately 52 minutes, 12 minutes, and 5 minutes consecutively to determine the maintenance schedules for ship operation intervals of 5 years, 2.5 years, and 1 year.

DEVELOPMENT OF MODEL-DRIVEN DECISION SUPPORT SYSTEM TO SCHEDULE UNDERWATER HULL CLEANING

Maritime industries are constantly searching for a method to enhance ship efficiency, with increasing concern about the environmental impact and rising fuel prices. Marine biofouling is one of the factors that increase ship fuel consumption. However, removing the fouling of the ship requires effort for hull maintenance. Due to the trade-off between conducting maintenance and performance degradation, this study presents the development of a Model-Driven Decision Support System (MD-DSS) to predict the optimum time for underwater hull cleaning for biofouling management. Five stages (sub-models) are employed to develop a DSS, namely: ship resistance estimation, estimation of additional resistance due to biofouling, an iterative-based method for determining the best time to conduct the hull cleaning, and an analysis report. The implemented algorithm was validated by comparing its result with a manually scheduled maintenance date. The DSS is able to determine the best time (date) for maintenance in all given scenarios. By giving two scenarios of different maintenance costs and different fuel prices, the optimisation results produce the same number of maintenances. Within 60 months, four to five hull cleanings are required. It is also found that when the optimal number of maintenances is known, then increasing this number will not have any impact on reducing the hull cleaning costs because the reduction in fouling does not significantly reduce the costs incurred for maintenance. During several trials of the DSS, it is shown that the system can generate maintenance schedules for different time intervals of ship operation within an acceptable time. It takes approximately 52 minutes, 12 minutes, and 5 minutes consecutively to determine the maintenance schedules for ship operation intervals of 5 years, 2.5 years, and 1 year.

Inspection of Underwater Hull Surface Condition Using the Soft Voting Ensemble of the Transfer-Learned Models.

In this study, we propose a method for inspecting the condition of hull surfaces using underwater images acquired from the camera of a remotely controlled underwater vehicle (ROUV). To this end, a soft voting ensemble classifier comprising six well-known convolutional neural network models was used. Using the transfer learning technique, the images of the hull surfaces were used to retrain the six models. The proposed method exhibited an accuracy of 98.13%, a precision of 98.73%, a recall of 97.50%, and an F1-score of 98.11% for the classification of the test set. Furthermore, the time taken for the classification of one image was verified to be approximately 56.25 ms, which is applicable to ROUVs that require real-time inspection.

A novel tool for cost and emission reduction related to ship underwater hull maintenance

International shipping plays a vital role in the world's transport system and economy. However, shipping faces challenges in terms of reducing its environmental and health impact, namely emission of greenhouse gases, air pollutants, and chemical substances to the marine environment. In particular, the roughness condition of underwater surfaces of a ship hull affects the ship's energy efficiency, with marine growth (biofouling) and mechanical roughness leading to propulsion powering penalties. Measures to control biofouling, using antifouling coatings and in-water hull cleaning, may also be associated with significant impacts to the marine environment. In the current study, a new tool is presented, HullMASTER (Hull MAintenance STrategies for Emission Reduction), which aims at enabling the shipping industry and authorities in the Baltic Sea region to make evidence-based decisions on hull maintenance strategies. HullMASTER simulates emissions to air and water, to calculate the differences in economic cost for operators, as well as health- and environmental damage costs between different hull maintenance scenarios. Validation of HullMASTER predictions against 40 vessel-years of in-service performance data on propulsive performance, with operations in the Baltic Sea region, shows good agreement, averaging within 5 percentage-point difference in propulsion penalty. Further, a scenario-based demonstration of HullMASTER on a general cargo vessel shows that, in the comparison between a silicone foul-release coating and business-as-usual scenario of a biocidal coating, retrofitting the coating to a foul-release coating can result in significant savings for society, i.e., along with marginal savings in cost for ship operators. Results for such comparisons and analysis will however be dependent on specific vessel cases and operational profiles, thence the value of an interactive tool such as HullMASTER.

Design parameter sensitivity analysis for SWATH with minimum resistance at design and service speeds

Parametric hull form is efficient in geometric modification, and can help to obtain new hull forms with excellent hydrodynamic performance. Achieving parametric hull modeling depends on the reasonable definition of design parameters. Currently, in parametric hull modeling and optimization, the lack of an effective parameter selection method usually results in blindness and inefficiency in the hull design. This paper provides an automatic calculation framework for SWATH (Small Water-plane Area Twin Hull) resistance at different speeds. A fully parametric SWATH model is established to realize automatic geometric transformation. SOBOL (Sobol’ quasi-random sequence) algorithm is used for space sampling. The sensitivity analysis of all the parameters of SWATH for resistance is carried out. The correlation study between design variables and resistance is performed and the correlation coefficients of all design parameters are given and discussed. Among the parameters of SWATH, 4 design parameters, those control the longitudinal deformation of the bow of the underwater hull, the transverse deformation of the stern, the position of the parallel middle body of the strut, and the inclination of the strut, respectively, are more sensitive to the resistance. The suggestions for the parametric design of SWATH are given based on the sensitivity analysis and optimization results.

Laivojen pohjien likaantumisen vaikutus kulkuvastukseen Itämerellä: Chow-Liu-puulla täydennetyn Naiivi Bayes -mallin soveltaminen aluksen kulun analysointiin

COMPLETE-hankkeen tavoitteena on ehkäistä haitallisten vieraslajien leviämistä Itämeren alueella. Leviämistä on tapahtunut merkittävästi laivojen painolastivesien mukana, mutta lajikkeita kulkeutuu merialueilta toisille myös vedenalaisiin runkorakenteisiin tarttuneina. Lisäksi biolikaantuminen kasvattaa aluksen kulkuvastusta ja sitä myötä polttoaineen kulutusta sekä hiilidioksidipäästöjä. Tällä hetkellä likaantumista rajoitetaan puhdistamalla pohjia sään­nölli­sesti kesäkaudella. Puhdistusajankohdat valitaan laivakohtaisesti pääsääntöisesti kokemukseen pe­rus­tuen. Myös puhdistuksilla usein koetaan olevan havaittavaa vaikutusta aluksen kulkuun ve­den halki, mutta mittauksiin perustuvia tietoja ei laivaväen käytössä ole. Nykyään laivojen järjes­tel­mistä on mahdollista tallentaa kulkudataa enenevissä määrin. Luotettavien johtopäätösten teke­mi­nen massadatasta vaatii kuitenkin asiaan soveltuvia työkaluja ja systeemin monien sekoittajien omi­nai­suuksien tuntemista. Tässä artikkelissa perehdytään Chow–Liu-puulla täydennetyn Naiivi Bayes -mallin hyödyntämiseen aluksen kulun analysointiin. Menetelmän etuina ovat las­ken­nal­li­nen tehokkuus ja luotettavuus kulkuvastuksen kausaatioiden tunnistamiseksi, vaikka käy­tettä­vis­sä olevaa dataa olisikin vain rajoitetusti.

Electrical Swath Ships with Underwater Hulls Preventing the Boundary Layer Separation

The body shapes of aquatic animals can ensure a laminar flow without boundary layer separation at rather high Reynolds numbers. The commercial efficiencies (drag-to-weight ratio) of similar hulls were estimated. The examples of neutrally buoyant vehicles of high commercial efficiency were proposed. It was shown that such hulls can be effectively used both in water and air. In particular, their application for SWATH (Small Water Area Twin Hulls) vehicles is discussed. In particular, the seakeeping characteristics of such ships can be improved due to the use of underwater hulls. In addition, the special shaping of these hulls allows the reducing of total drag, as well as the energetic needs and pollution. The presented estimations show that a weight-to-drag ratio of 165 can be achieved for a yacht with such specially shaped underwater hulls. Thus, a yacht with improved underwater hulls can use electrical engines only, and solar cells to charge the batteries.

Numerical Simulation of Hydrodynamic Characteristics of Underwater Hull Cleaning Robot Using CFD Techniques

In this article, an underwater hull cleaning robot model based on propeller thrust adsorption is established for near-wall conditions. By using a computational fluid dynamics method, which is proven feasible by comparing a calm water resistance simulation with its experimental data, the influence of floating body shape and wall distance on its hydrodynamic characteristics is studied. Then, the body force propeller model is used to analyze the interaction between the propeller flow field and the flow field around the underwater cleaning robot. Compared with the cuboid floating body, the results show that the streamlined appearance can greatly reduce front high-pressure area, the pressure drag between the front and rear ends, and the viscous resistance. Its drag coefficient is reduced by 11.5%. The presence of the hull will increase the pressure drag and viscous resistance of the underwater hull cleaning robot, which is similar to the "shallow water blockage effect" of a ship. For this model, the decrease in the wall distance results in a progressive increase in resistance and drag coefficient. As the wall distance is .15 m, the drag coefficient of the underwater hull cleaning robot increases by 4.55%, compared with the limitless water field. For the body force propeller model, the study indicates that when the flow velocity is constant, both the resistance in the forward direction and the adsorption force of the underwater hull cleaning robot increase with the increase in rotation speed of the propeller. The thrust propeller generates a higher increase in resistance and a lower increase in adsorption force compared with the adsorption of the propeller. When the rotation speed is constant, the resistance of the underwater hull cleaning robot increases, with the increase in the flow velocity, and the adsorption force of the underwater hull cleaning robot first decreases and then increases. Therefore, it must be fully considered that the significant influence of the hull and the propeller on the underwater hull cleaning robot can provide theoretical guidance for future related design and research.

The Impact of the Underwater Hull Anti-Fouling Silicone Coating on a Ferry’s Fuel Consumption

There are well-known specifics of ro-pax ferry shipping, such as the time factor as a consequence of keeping a regular timetable and the priority given to minimizing heeling, pitching, and rolling caused by maximum focus on passenger comfort and ro-ro cargo safety. It is also extremely important to control the ferry’s fuel consumption, being one of the most important cost components. The aim of the article is to draw the attention of shipping company managers to the great potential that lies in the use of routine operational data, collected exclusively on board the ferries. It is worth noting that the research in this paper is based on standard office software packages rather than advanced statistical methods of data analysis, which are usually not accessible for shipping managers. Contrary to typical ocean-going vessels, there are a number of factors that need to be taken into consideration when analyzing ro-pax ferry fuel consumption. Moreover, these factors occur, in many cases, accidentally and, thus, they are difficult to observe on board the ferry without utilizing expensive and time-consuming methods. The possibility of fuel control is important not only for economic reasons but also due to air pollution caused by engine exhausts. The article presents an estimation of increased fuel consumption caused by the degradation of the hull silicone anti-fouling coating. The presented estimations of fuel consumption may be treated as the base for calculations of the economic effectiveness of ferries. The attempt to resolve the above-mentioned problem was made on the basis of research on a real ferry, which took place on the Świnoujście-Trelleborg line between 2007 and 2019.

Performance of Rosin Modified Antifouling Coated on Mild Steel Surface at Various Immersion Orientation

Steel is one of materials that been used as a hull to build a ship. Steel are well known as strong, easy to fabricate and can withstand higher loading. Major problem for steel in shipbuilding are corrosion and marine fouling. Antifouling paint are applied at underwater hull paint to protect and slowing the microorganism growth, plant and animal that attached to the ship bottom hull. Important additive in antifouling paint known as Tributyltin (TBT) was previously observed good efficiency in prevent marine growth, however International Maritime Organization (IMO), in 2008 banned the usage of TBT due to abnormal growth of oyster shell. Thus, it is crucial to focus on an environmentally friendly antifouling paint and additive. Rosin modified paint is one of natural base of paint matrix that extract from pine tree. Performance of rosin modified with commercial biocide additive at various orientation are evaluate by referring to standard testing method on antifouling panels in shallow submergence. Rosin modified base observed good interaction with primer and steel substrate. Rosin modified antifouling (AF) coating for orientation 0º, 90º and 180º shows less than 4% marine growth after 30 days of immersion. AF coated at 0º and 90º -a orientation observe efficient protection with no marine growth occurred after 30 days of immersion.

Pressure Hull Design Methods for Unmanned Underwater Vehicles

This paper describes design methods for the plastic hull of an Unmanned Underwater Vehicle (UUV), with a particular focus on its cylindrical body and nearly spherical domes at the ends. With the proposed approach, the methodologies reported in the literature were compared, and suitable modifications and improvements were investigated and implemented to extend the classical theories and data to this case study. The investigated underwater vehicle, named FeelHippo, was designed and assembled by the Department of Industrial Engineering of the University of Florence. Its main hull is composed of an extruded PMMA (PolyMethyl MethAcrylate) cylinder and two thermoformed PMMA domes. Breakage of the hull results in destructive phenomena, namely, yielding and buckling. An experimental campaign and FEM (Finite Element Method) analysis were carried out to complete the theoretical study, and the collapse pressures were compared with the derived design values. In conclusion, the proposed innovative method is a lean and effective technique for designing underwater hull domes and predicting the collapse pressures.