Naval Architects Research Articles

Epoxy Resin Biocomposites Reinforced with Flax and Hemp Fibers for Marine Applications

A broader application of biocomposites still faces many challenges regarding structural integrity, environmental resistance, and biodegradability. These issues are particularly important when their marine applications are considered. Therefore, this paper seeks to address the hygroscopicity, mechanical properties, and biofouling resistance of biocomposites made of epoxy resin with 28 m% bio-based carbon content reinforced with flax and hemp fibers. A series of experiments are performed to acquire water absorption rates, saturation limits, mass increase, tensile and flexural properties, interlaminar shear strength, impact resistance, and mass gain due to biofouling. All tests of mechanical properties are conducted before and after immersion in seawater. The acquired saturation limits of flax/epoxy and hemp/epoxy biocomposites amount to 7.5% and 9.8%, respectively. The water uptake causes the tensile and flexural properties to decrease by 26–74%, while interlaminar and impact strength increase for flax/epoxy and decrease for hemp/epoxy biocomposites. In addition, it is observed that in almost all cases, flax/epoxy has superior properties compared with hemp/epoxy biocomposites. It is expected that this research will motivate naval architects and classification societies to consider biocomposites as prospective hull materials that provide both structural integrity and environmental sustainability.

Sodium chloride inhibits effective bubbly drag reduction in turbulent bubbly Taylor-Couette flows.

Using the Taylor-Couette geometry we experimentally investigate the effect of salt on drag reduction caused by bubbles present in the flow. We combine torque measurements with optical high-speed imaging to relate the bubble size to the drag experienced by the flow. Previous studies have shown that a small percentage of air (4%) can lead to dramatic drag reduction (40%). In contrast to previous laboratory experiments, which mainly used fresh water, we will vary the salinity fromthat of fresh water to the average salinity of ocean water. We find that the drag reduction is increasingly more inhibited for increasing salt concentrations, going from 40% for fresh water to just 15% for seawater. Salts present in the working fluid inhibit coalescence events, resulting in smaller bubbles in the flow and, with that, adecrease inthe drag reduction. Above a critical salinity, increasing the salinity has no further effect on thesize of bubbles in the flow and thus the drag experienced by the flow. Our new findings demonstrate the importance of sodium chloride on the bubbly drag reduction mechanism, and will further challenge naval architects to implement promising air lubrication systems on marine vessels. This article is part of the theme issue 'Taylor-Couette and related flows on the centennial of Taylor's seminal Philosophical Transactions paper (part 1)'.

"TEACHING ENGLISH TO NAVAL ARCHITECTURE STUDENTS IN ROMANIA "

Learning English by naval architects is important for a number of reasons. Different people can communicate with one another with the help of English. Secondly, all advanced knowledge in naval architecture is available in English. The results of the latest researches come to Romania through the medium of English. If we give up English, we will lag behind in the higher fields of study. Today the world has become one family. It is all due to English. English is an international language. English has become a part of Romanian life. In this paper I have tried to mention the problems faced by teachers of English in teaching students of Naval Architecture and Technology, at the same time problems faced by students in learning English. I have also mentioned some suggestions and ways to develop all skills related to English Language that might be useful for both-students and teachers.

"Dronization" of the sea - ships of the future

Maritime areas cover 70% of the surface of the Planet, see the transit of 80% of world trade and accommodate submarine cables through which 99% of telecommunications pass. This carpet of the bottom of the oceans contributes to a wave of digitization of land, air and sea spaces, thus challenging human beings. The development of aerial drones and the autono-mous car has largely inspired the industry of the maritime world. The smart shipping rev-olution is underway. Nothing seems able to prevent it as the expected benefits are numer-ous. Reducing the number of sailors on board ships will reduce the number of premises devoted to human presence, thus freeing up space for that of the goods transported, and will give naval architects freedom to design more hydrodynamic shapes adapted to the as-signments. On this aspect, we are witnessing a transition from automation – which has already enabled significant crew reductions – to autonomy, which will amplify the phenom-enon.

Analysing Ancient (Viking) Longship Structures

The Nordic longships of the 9th to 11th Centuries were perhaps the preeminent fast assault ships of the period. Modern engineering analytical tools have been employed from time to time to investigate their stability, performance and structural characteristics. The latter is perhaps the most challenging, since the physical problem is that of a hydro-elastic body in rough seas, constructed of a material with highly variable mechanical properties, fastened together by rivets, treenails, nails, spikes, lashings and wedges of uncertain joint efficiency. The corresponding analysis is potentially considerably more complex than the ‘linked-chain’ method commonly employed in modern design offices to establish acceptable scantlings, i.e. classification society rule loads and criteria together with reliable published material property data which are the essential inputs to scantling formulae/finite element analyses (FEA). This paper outlines one small craft naval architect’s view of the issues involved in applying the standard structural design method to the analysis of a ship type which is radically different from modern craft and in so doing identify issues which may be of interest to modern naval architects analysing unconventional lightweight structures.

‘Careers for women’: BBC women’s radio programmes and the ‘professional’, 1923–1955

ABSTRACT In May 1923, the fledgling BBC launched its first daily programme to be aimed at a female audience, the short-lived Women’s Hour. A popular feature was talks on careers: museum curator, almoner, optician, solicitor, athletics organiser were amongst the newly possible professions that were discussed. By the 1930s, female politicians, lawyers and childcare specialists were discussing their work as established experts, while during the Second World War, naval architects, photographers and life insurance underwriters were lauded as novel female jobs. Woman’s Hour, which was launched in 1946, as well as frequently featuring expert female guests, grappled with a post-war landscape where a return to a career was becoming a possibility for women, once children were grown. This article uses the BBC’s early radio programmes for women as a means to explore the ways in which professional women were represented to its listening public, over a period of thirty-two years.

Maritime Autonomous Surface Ships: Automation Transparency for Nearby Vessels

In the future, maritime autonomous surface ships (MASS) will become more advanced, and mariners will move from the bridge to remote operation centres. To avoid dangerous situations and frequent intervention from the operators, a MASS needs to perceive the environment and calculate the current state and future intention of nearby ships. Another challenge for a MASS is to explain the decisions of its algorithms and make the artificial intelligence’s decisions transparent to not only the operators, but also external stakeholders, such as passengers, vessel traffic services, and nearby ships. This is called automation transparency. In this paper we focus on how MASS, through various means of maritime communication, can (1) express their own state and intention to other ships and (2) perceive other ships’ state and intention. Towards that, we first analyse current maritime communication methods in terms of how well they can be expressed and perceived by today’s MASS in comparison to traditional ships. Next, we analyse which gaps in their communication should be focused on to maximise safety at sea. Finally, we present multiple design recommendations for naval architects, human factors engineers, and interaction designers who are designing and building the next generation of MASS.

A preliminary risk assessment on development the fuel gas supply system of a small LNG fueled fishing ship

Liquefied natural gas (LNG) as an alternative marine fuel is attracting interest from a variety of parties in its use for large and small ships due to the role in improving climate change. However, a broader range of ships including in particular ferries, cargo and offshore support ships is operating with dual-fuel LNG engines. Compared to the conventional marine fuels, the use of LNG could offer an attractive alternative in the fishing industry for reducing exhaust gas emissions in the air in terms of NOx, SOx, CO2, and particle matter (PM), as well as possible economic benefits. In the context mentioned above, our research team has been developing a concept design for small LNG fueled fishing ships. A Hazard Identification (HAZID) study was carried out as one of the essential stages throughout the unique system development of the LNG fueled fishing ship. The HAZID study was done to gain a better understanding of the proposed idea and to identify the significant difficulties or risks that could jeopardize the unique fishing ship design's safety. For hazards with unacceptable risks or as low as reasonably possible (ALARP), additional course of actions and recommendations were discussed and proposed in the safety action register. The results of this study will help the naval architects to follow up the detailed system designs.

A modelling and simulation framework to assess integrated survivability of naval platforms in high threat environments

Integrated Survivability analysis of naval platforms incorporates the domains of susceptibility, vulnerability and recoverability, measured temporally. These are accepted as key elements when holistically assessing naval platform survivability against threat scenarios. Conversely, traditional naval platform survivability assessment only considered the vulnerability domain or a combination of susceptibility and vulnerability. However, emphasis is now placed on the interdependence of susceptibility, vulnerability and recoverability. Unfortunately, there are shortcomings with historic survivability modelling and assessment capabilities pertaining to Integrated Survivability. This has resulted in the need to clearly define the concept of Integrated Survivability, and identify modelling requirements to assess platforms exposed to the threat environments. A naval platform Integrated Survivability assessment capability, derived from those survivability modelling requirements, will enable naval architects and mission planners to quantify the effects of platform survivability. Assessments will consider platform safety systems and survivability control measures, and changes to those systems and control measures. Outcomes from the assessments will contribute to platform configuration optimisation for resilience against the threat environment and enable mission success. This paper presents the need for an Integrated Survivability assessment capability, defining relevant terminology, and elucidating modelling requirements to develop such a capability.

PRACTICAL SHIP DESIGN CONSIDERATIONS FOR MISSION MODULARITY

In this paper, the authors seek to review the direction mission modularity has been taking us and look forward to how modularity will influence future warship design, and some of the challenges that the naval architect will need to address.

Seakeeping and Safety Assessment of Fishing Vessel 30 GT

In Indonesia, many fishing vessels are made from generation to generation in a traditional way. As a result, the ships built did not comply with the regulations and permits of the naval architects. The fishing industry is one of the most dangerous because it works on the high seas. Therefore the performance in hydrodynamics and safety should be evaluated on these traditional vessels. The main objective of this research is to evaluate the hydrodynamic performance and safety of fishing vessels. Following standard specifications or criteria, seakeeping performance is evaluated using Maxsurf Ship Design software. Assessment of existing safety equipment uses IMO (International Maritime Organization) regulations and the Torremolinos protocol. As a result, the ship can only operate at a wave height of 0,1-0,5 meters or undersea state 3. Ship safety inspections reveal that they still do not meet the required requirements and do not have the necessary equipment specified by the World Maritime Organization (IMO) .

Experimental study on the effect of biomimetic tubercles on the drag of a flat plate

The necessity to improve the hydrodynamic performance of marine vessels has confirmed the urgency of conducting further investigations on biomimetic tubercles. In this work, towing tank tests were conducted at a range of speeds on conveniently prepared flat plates coated with 3D printed humpback whales mimicked tubercles.The results showed that the artificial tubercles induced a drag reduction of up to 1.3% compared to the bare flat plate. Following the experimental campaign presented, some relevant considerations for ship owners and naval architects will be proposed.

Optimization Modelling of a Catamaran Hull Form towards Reducing Ship’s Total Resistance

Due to the increasing of fuel prices and volatile of environmental regulations, it is a challenge for Naval Architects to design a ship dealing with an optimum ship’s total resistance. The conventional design of catamaran hull has not satisfied yet to reduce the ship’s total resistance. This paper presents a numerical investigation into gaining sufficient reduction of the ship’s total resistance of catamaran through optimizing her hull form. To achieve this research objectives, a numerical optimization modelling coupled with a Computational Fluid Dynamics (CFD) approach has been successfully conducted. Several parameters such as length, beam and draft of catamaran hull have been taken into account towards reducing the ship’s total resistance. Here, the simulation constraints are applied to obtain the optimum dimension, where the length, beam and draft of the catamaran hull were optimized within the range of 1.2 m to 1.5 m, 0.11 m to 0.14 m and 0.07 m to 0.08 m, respectively. In general, the optimization simulation revealed that the optimum dimension of the catamaran hull resulted in reduction of the total ship’s resistance. The results showed that the optimum length, beam and draft of hull led to reduce by 21.08%, 16.95% and 17.91%, respectively. Merely, this numerical optimization simulation provides a useful way for reducing the total ship’s resistance of the catamaran at the preliminary design stage.

Flow Visualization, Hydrodynamics, and Structural Response of a Flexible Wedge in Water Entry Experiments

_ In this article, a free-falling flexible wedge into calm water is experimentally studied to understand the relationship between the spray root, peak pressure, and structural response. High-speed cameras are employed to record the spray root propagation, whereas hydrodynamic loading is measured with an array of pressure transducers. Stereoscopic-Digital Image Correlation (S-DIC) is used to measure deflection on the bottom of the wedge during the impact. Experiments are conducted from different drop heights to study the effect of impact velocity. Results are interpreted in light of an experimental data set of a rigid wedge of comparable dimensions. The comparison between the rigid and flexible wedges shows that due to fluid-structure interaction, the evolution of the spray root on a flexible wedge is slightly delayed compared to the rigid one. Introduction Nowadays, high-speed planing craft are widely used in commercial, recreational, and naval applications. As the growth in utilization of these vessels is observed, naval architects strive to improve the overall performance while the safety metrics are adequately maintained. One of the major concerns that challenges both the performance and structural strength of small high-speed craft is hull slamming. Once the vessel is subject to incoming waves, the hull repeatedly becomes airborne and then impacts the water surface. These slams cause operators to reduce the speed, and the maneuverability of the vessel is also influenced. Additionally, slamming can lead to the serious injury of sailors in rough sea conditions. Severe motion of the vessel because of the impact may also adversely affect the operability of equipment on board, meaning that autonomous vessels are still vulnerable to these types of loading events. As a result, it is crucial to study and understand the slamming in high-speed craft in order to mitigate its negative effects.

Horizontal impact loads and torsional moment induced by partial cargo shifts

Previous studies demonstrate that significant cargo shifts occurred in all cargo holds of vessels in carriage of nickel ores may lead to catastrophic consequences of ship capsizing and sinking. Nevertheless, partial cargo shifts, despite its seldom occurrence in other types of vessels, are not unusual in bulk carriers, specifically for those with nickel ores which tend to liquefy as vessels experience long-time engine vibrations or unfavorable oblique waves. Regrettably, it has not been well described in previous literatures, therefore overlooked by ship operators and naval architects in ship structural design. The instantaneous impact loads to vessel's structures induced by partial cargo shifts, thus, remain unclear. Despite partial cargo shifts being unlikely to lead to life lost or ship capsizing, critical damage to cargo holds, shell plates and precise apparatuses in the wheelhouse can be identified frequently, sometimes even causing ship a hazardous list of 6–15°. Unfortunately, a number of similar accidents occurred in S.E. Asia waters have been found without reporting these accidents to IMO due to various reasons. The instantaneous impact loads, involving the torsional moments and horizontal sectional loads, initially overlooked by plenty of naval architects but subsequently estimated by our research team, are really huge, usually giving rise to a dangerous list of vessels as well as apparent or underlying damage to vessel's configurations. Conventional approaches, such as potential flow theory, volume of fluid method, moving particle semi-implicit method, smoothed particle hydrodynamics, etc., are significantly limited by their unsatisfactory precision in predicting and calculating those extraordinary loads. Here we estimate the torsional moments and horizontal sectional loads in oblique waves at various exciting rolling frequencies using improved Finite Element approach. The final results yielded from the model tests are strikingly in line with that from the numerical approach, manifesting that the modified numerical method behaves in a reasonable manner in tracking and capturing the complicated surface of large viscous fluid.

WARGEAR: ‘Real time’ generation of detailed layout plans of surface warships during early stage design

Generating detailed warship layouts is crucial to check technical feasibility and performance consistent with emergent requirement elucidation during early stage design. However, generating feasible detailed layouts is a complex and time consuming task.Even today, detailed layout plans are often manually drawn using CAD software, taking up to 150 work hours to complete a single feasible layout plan, as found by the Netherlands Defence Materiel Organisation (DMO). As a result, the number of layout variations that can be generated and analysed is limited. This typically means that further detailed layout generation is postponed, increasing the risk of costly sizing and integration issues later in the design process. Therefore, a method that enables rapid insight into layout sizing issues is required.This paper elaborates on the mathematical working mechanisms of the WARship GEneral ARrangement (WARGEAR) tool, that has been developed to support naval architects in detailing ship arrangements to space level in a matter of minutes. Contributions are: (1) a probabilistic staircase placement algorithm, (2) a network-based approach combined with probabilistic selection for allocation of spaces to compartments, (3) the use of cross-correlation to quickly arrange spaces, and (4) a ‘carving’-based approach to ensure connectivity. A representative WARGEAR application case study is presented. This test shows how WARGEAR is able to confirm the feasibility of future warship arrangements at a high level of detail within minutes.

Web application with data centric approach to ship powering prediction using deep learning

<h2>Abstract</h2> This work describes an AI-based web application to predict passenger ship powering requirements. The data centric approach is developed based on the actual passenger ship design data as a design tool to assist naval architects to quickly estimate the ship brake power. It emphasised on the preliminary design stage to minimise design tasks and laborious calculations. Based on the study, it is observed that the model shows good agreement to the existing empirical method results with 10% mean absolute errors. Significantly, this presents the approach ability to facilitate faster and effective preliminary design, and scalability for large and complex systems.

Topology optimization of an oil tanker bulkhead subjected to hydrostatic loads

In the field of Naval Architecture, the conventional approach to design any vessel is to follow the classification societies’ rules to ensure adequate strength and structural integrity. Nowadays, owners’ demands and purposes of vessels are changing dramatically. To mitigate these demands, sometimes it is necessary to design new types of structures, but the classification society’s rules are not sufficient to prepare these advanced designs. Moreover, Naval Architects are always eager to minimize the lightweight of a vessel as this is directly related to cost and carrying capacity. Topology optimization has become a powerful tool for designing structures in an optimized way. The concept of topology optimization has been utilized by the automotive and aerospace industry for almost thirty years where problems associated with solutions meant to satisfy maximum stiffness and structural integrity with minimum weight which are of utmost importance. However, in the field of marine and offshore structures, the use of topology optimization is infrequent. As structural optimization aims to design structures under certain constraints to achieve better strength and lower cost, the introduction of this technique in ship structure can be lucrative. In this paper, a methodology to apply structural topology optimization in the field of ship design is presented. An Oil Tanker Bulkhead has been selected for this study. SIMULIA ABAQUS software is used in this regard. Topology optimization has been performed by minimizing the strain energy of the component as the objective function and a target stiffness and material volume of the structure as design constraints. Finally, the results demonstrate the general applicability of the methodology presented for obtaining the geometrical layout of the structure.

ENABLING TECHNOLOGY AND THE NAVAL ARCHITECT 1860-2010

Enabling technology permits the naval architect to do more with fewer resources, increasing output, decreasing cost and improving productivity, with the resulting benefits being widely distributed in a worldwide economy. For example a bulk carrier’s energy consumption per ton-mile today is less than 3% of what it was a century and half ago – due to more efficient machinery, larger hulls with lower resistance per ton and improved propulsive efficiency, yet with higher speed and shorter port times.

ON THE ROLL DAMPING OF AN FPSO WITH RISER BALCONY AND BILGE KEELS

Although the topic of roll damping of vessels at sea is already brought to the attention of naval architects by Froude more than 100 years ago, the physics of it remain intriguing, even today. An accurate prediction of the motions of offshore structures in harsh environments, designed for 25 years continuous operation, is the topic of this paper. Model test experiments for two FPSO’s developed by SBM for Petrobras are discussed. It is shown that the FPSO submerged riser balcony on one side of the vessel contributes to the roll damping through similar physics as the bilge keel does. Flow memory effects are discussed in detail since these are shown to have a noticeable effect on the roll damping coefficients. The paper further employs 3D CFD simulations to enhance the understanding of the fluid behaviour around the FPSO appendages, necessary to construct a rational and accurate roll damping model in the future.