Light Ship Research Articles

Detection Method of Key Ship Parts Based on YOLOv11

The current ship target detection algorithm is not adaptable to changes in target size and position, and its detection accuracy and speed are difficult to balance in the process of algorithm improvement. In particular, there is little research on the detection of key parts of ships. In this paper, an improved YOLOv11 ship key location detection algorithm is proposed. It is difficult to balance the relationship between detection efficiency and model complexity using current key parts detection algorithms. The processing performance of deforming key parts according to the algorithms is not strong. Moreover, the algorithms’ detection performance of occluding overlapping targets and small-size targets is not high. In view of the practical problems existing in the algorithms and the realistic demand for real-time and accurate detection of key parts of targets on dynamic ships at sea, three aspects of improvement on YOLOv11 are proposed. The visible light ship key position dataset is then constructed for the experiment. The experimental results show that the improved YOLOv11 network in this paper can detect the key position information of ships more accurately and efficiently, effectively balance the relationship between model accuracy and speed, overcome the interference of dynamic factors, improve the fine interpretation of dynamic ship information at sea, and provide a feasible technical approach for accurately and precisely mastering ship information at sea and realizing real-time sea area detection.

Effect of ice class to vessel fuel consumption based on real-life MRV data

Effect of ice class to vessel fuel consumption based on real-life MRV data

Changing the frequency of heеling test for small fishing vessels during their operation

Loss of stability of the vessel belongs to the category one of the most dangerous disasters, several ships perish each year from capsizing around the world, and in some years the number is measured in tens. Therefore, the ships should carry out constant of monitoring of the main parameters of stability. The displacement and height of the center of gravity above the main plane a of light ship increase during operation. This growth is due to repairs, modernization, bringing the vessel into compliance with the new requirements of the IMO Conventions, and improvements in working and living conditions. An analysis of the records of the ships MRTK of the Baltica type heeling test showed that their displacement increased by 0,5-14,8 tones and that the increase in height of the center of gravity above the main plane was about 5,47 centimeters, and a maximum increment has reached of 15 centimeters. Such changes in the characteristics of a light ship may result in a disruption of the vessel's stability in operational load cases. Calculations of changes in displacement and height of the center of gravity above the main plane of light ship for Baltika type MRTK and Obolon type SRTM (333 design) under the worst-case load in terms of stability were made in the article. Analysis of the plotted graphs changes static stability curve for MRTK Baltika type showed, that during 10 years of operation, maximum metacentric arm decreased by 0,05 m, and change of height of the center of gravity above the main plane of the light ship made 0,1 m. For the SRTM Obolon type the maximum shoulder of the dynamic stability curve decreased by 0,038 m and the change in the height of the center of gravity above the main plane for the light ship 0,05 m. All this suggests that a heeling test for small craft should be carried out more frequently than every 10 years.

ON THE MACRO HYDRODYNAMIC DESIGN OF HIGHLY EFFICIENT MEDIUM- SPEED CATAMARANS WITH MINIMUM RESISTANCE

A new class of fuel-efficient and environmentally friendly twin-hull vessels is currently under development. Compared to high-speed catamarans, a significant reduction in speed combined with an increase in deadweight tonnes will lead to a highly efficient medium-speed catamaran design. Recently-built conventional and high-speed ferries are compared to each other in terms of length, speed, deadweight and transport efficiency to classify the new design. The goal of this study is to find a preliminary macro design point for minimum total resistance by considering the main particulars of the catamaran vessel: block coefficient, prismatic coefficient and slenderness and separation ratios of the demihulls. Publications containing recommendations towards the optimum hull form parameters for moderate Froude numbers are reviewed and existing experimental data analysed to identify parameters for this new class of vessel. Designs with varied L/BOA-ratios and constant deck area are compared to find configurations of low total resistance for carrying a nominated deadweight at a particular speed, the associated change of the light ship weight has been taken into account. Two different model test series of catamaran models have been considered and their resistance curves agreed to each other. Recommendations are made; with the most important being the vessel should not exceed a speed of Fr = 0.35, with optimal prismatic coefficients around CP ≈ 0.5 and low transom immersion. This study presents the preliminary design of medium-speed single and twin-hull vessels for operations close to hump speed.

Fatigue crack growth of new FML composites for light ship buildings under predominant mode II loading condition

The use of light but strong materials is largely studied in various area of the shipbuilding, this because the need of reducing the weight, and especially the weight of all the structures above the main deck assume primary importance for the stability. Traditionally in fast boats like fast ferries, hydrofoils, patrol boats, the typical materials are Aluminum alloy or composites, both those materials have advantages and disadvantages, but the new development of technologies made possible to combine them, in order to have a new material, combining the advantages of both, in terms of fatigue resistance, firefighting characteristics. In this paper, predominant mode II fatigue delamination tests of fiber metal laminates made of alternating layers of 2024-T3 aluminum alloy sheets and unidirectional E-Glass/epoxy laminates are presented. Several experimental tests are carried out employing the End Notched Flexure fixture and a progressive damage model is used to simulate the damage accumulation in the aluminum-composite interface, in the localized area in front of the crack tip, where micro-cracking or void formation reduce the delamination strength during fatigue tests. In particular, the numerical model is based on the cohesive zone approach and on the analytical definition of a damage parameter, directly related to the fatigue crack growth rate da/dN. The numerical model, implemented in ANSYS environment, uses a fracture mechanics-based criterion in order to determine the damage propagation. In particular, the study has allowed to determine the damage model constants that are used for numerical verification of the experimental results.

Optimal dimension design of a hatch cover for lightening a bulk carrier

ABSTRACT : According to the increase of the operating cost and material cost of a ship due to the change of international oil price, a demand for the lightening of the ship weight is being made from various parties such as shipping companies, ship owners, and shipyards. To satisfy such demand, many studies for a light ship are being made. As one of them, an optimal design method of an existing hull structure, that is, a method for lightening the ship weight based on the optimization technique was proposed in this study. For this, we selected a hatch cover of a bulk carrier as an optimization target and formulated an optimization problem in order to determine optimal principal dimensions of the hatch cover for lightening the bulk carrier. Some dimensions representing the shape of the hatch cover were selected as design variables and some design considerations related to the maximum stress, maximum deflection, and geometry of the hatch cover were selected as constraints. In addition, the minimization of the weight of the hatch cover was selected as an objective function. To solve this optimization problem, we developed an optimization program based on the Sequential Quadratic Programming (SQP) using C++ programming language. To evaluate the applicability of the developed program, it was applied to a problem for finding optimal principal dimensions of the hatch cover of a deadweight 180,000 ton bulk carrier. The result shows that the developed program can decrease the hatch cover's weight by about 8.5%. Thus, this study will be able to contribute to make energy saving and environment-friendly ship in shipyard.

Study on the Influence of Modularization on Warship General Design

The versatility of ship is reflected in the modularization design. On the basis of summarizing the module and modular theory, the modularization design concept is applied to the design procedure of ships. This paper studied the impact of modularization on the ship general design, proposed an idea of functional areas. According to the different tasks, the light ship can be divided into three types: civilian type, guard type and military type.

Elastic Soft-Core Sandwich Plates: Critical Loads and Energy Errors in Commercial Codes Due to Choice of Objective Stress Rate

Most commercial finite element codes, such as ABAQUS, LS-DYNA, ANSYS and NASTRAN, use as the objective stress rate the Jaumann rate of Cauchy (or true) stress, which has two flaws: It does not conserve energy since it is not work-conjugate to any finite strain tensor and, as previously shown for the case of sandwich columns, does not give a correct expression for the work of in-plane forces during buckling. This causes no appreciable errors when the skins and the core are subdivided by several layers of finite elements. However, in spite of a linear elastic behavior of the core and skins, the errors are found to be large when either the sandwich plate theory with the normals of the core remaining straight or the classical equivalent homogenization as an orthotropic plate with the normals remaining straight is used. Numerical analysis of a plate intended for the cladding of the hull of a light long ship shows errors up to 40%. It is shown that a previously derived stress-dependent transformation of the tangential moduli eliminates the energy error caused by Jaumann rate of Cauchy stress and yields the correct critical buckling load. This load corresponds to the Truesdell objective stress rate, which is work-conjugate to the Green–Lagrangian finite strain tensor. The commercial codes should switch to this rate. The classical differential equations for buckling of elastic soft-core sandwich plates with a constant shear modulus of the core are shown to have a form that corresponds to the Truesdell rate and Green–Lagrangian tensor. The critical in-plane load is solved analytically from these differential equations with typical boundary conditions, and is found to agree perfectly with the finite element solution based on the Truesdell rate. Comparisons of the errors of various approaches are tabulated.

On The Macro Hydrodynamic Design Of Highly Efficient Medium-speed Catamarans With Minimum Resistance

A new class of fuel-efficient and environmentally friendly twin-hull vessels is currently under development. Compared to high-speed catamarans, a significant reduction in speed combined with an increase in deadweight tonnes will lead to a highly efficient medium-speed catamaran design. Recently-built conventional and high-speed ferries are compared to each other in terms of length, speed, deadweight and transport efficiency to classify the new design. The goal of this study is to find a preliminary macro design point for minimum total resistance by considering the main particulars of the catamaran vessel: block coefficient, prismatic coefficient and slenderness and separation ratios of the demihulls. Publications containing recommendations towards the optimum hull form parameters for moderate Froude numbers are reviewed and existing experimental data analysed to identify parameters for this new class of vessel. Designs with varied L/BOA-ratios and constant deck area are compared to find configurations of low total resistance for carrying a nominated deadweight at a particular speed, the associated change of the light ship weight has been taken into account. Two different model test series of catamaran models have been considered and their resistance curves agreed to each other. Recommendations are made; with the most important being the vessel should not exceed a speed of Fr = 0.35, with optimal prismatic coefficients around CP ≈ 0.5 and low transom immersion. This study presents the preliminary design of medium-speed single and twin-hull vessels for operations close to hump speed.

Research on shafting alignment considering ship hull deformations

Ship hull deformation is one of the most significant influences on propulsion shafting alignment. Based on the calculation fundamentals of ship hull deformations, a new method of shafting alignment considering ship hull deformations is proposed in this paper. Ship loadings, wave loads and environment temperature differences in some extreme conditions, as well as elastic constraints, are simulated and applied to the finite element model of 76,000 DWT product oil tanker, so that ship hull deformations can be solved. Then, the deformations of the double bottom are converted to bearing offsets, which behave as boundary constraints for shafting alignment calculations. Taking the condition of light ship in calm water as a reference, the impact of hull deformations on shafting alignment is analyzed and optimized shafting alignment considering ship hull deformations is realized.

The role of local wintertime atmospheric heat flux in determining springtime temperature variability in the northern Middle Atlantic Bight during 1965–1973

Abstract This project examines the role of local atmospheric forcing during the transition from relatively cold wintertime to relatively warmer springtime temperatures in the northern Middle Atlantic Bight (MAB) region during 1965–1973. A one-dimensional water column model is run for eight consecutive winter seasons with local surface heat flux used as the only external forcing. Historical data from the Nantucket Light Ship, along with modeled radiation estimates for New York and Boston are used for the heat flux calculations. Two model simulations were made for each winter season, allowing for both a qualitative and quantitative comparison of model output with observed regional temperature variability and with observed temperature changes measured at Nantucket Lightship (NLS). Interannual variability (IAV) in local atmospheric heat flux during wintertime is shown to be a dominant factor in determining springtime temperature conditions during the study period. However, the residuals from a regression analysis suggest that advective processes may have contributed to the observed temperature variability, although it is believed that the advective influence is secondary to local surface heat flux in the northern MAB for this study period.

Engineering Analysis on Vibration Characteristics of Merchant Vessels with Theoretical and Onboard Test Approaches

Recent development of ship design, such as flexible hull structures with somewhat light ship weight in terms of larger/longer/wider principal particulars and long-stroke diesel engine of high brake horsepower, has been demonstrated dramatically. Nevertheless, this kind of ship design concept harmfully degrades system stability of electronic instrumentation and operating performance of human beings in sea service. Therefore practical prediction on structural vibration behavior of designed vessels is of primary concern and has to be taken into account at the preliminary design stage. Two theoretical approaches, preliminary prediction by empirical formula and numerical solutions by finite-element technique (matrix analysis methodology), are briefly reviewed. An onboard test system for structural vibration measurement is developed and comprehensively described. In fact, a standard procedure of data acquisition and analysis system for structural vibration measurement is already set up to deal with several kinds of vibration research work in practical engineering fields. Natural frequencies of vibration behavior for a 1200 TEU container vessel are checked out by preliminary prediction of empirical formula and measurement data from onboard tests. Moreover, a comparison study by finite-element analysis and full-scale measurement is also performed on vibration characteristics of hull structures. The amplitude of vibration acceleration induced by unbalanced moment of the main engine is calculated for any point of hull at the resonance condition and the installation of an electrical balancer onboard is taken into account for vibration countermeasures also. All approximate predictions, compared with onboard test results, are found to meet with an acceptable level of engineering accuracy. The practical package of approximate approaches in both theoretical and onboard test aspects to investigate vibration characteristics of structures, for instance, hull, machinery, piping, and shafting system, in universal service is quite reliable and easily performed on portable computers for extensive engineering applications.

Fast Attack Combatant for Near‐Shore Operation

ABSTRACT The technologies of advanced naval engineering were used to design a corvette‐size vessel which transited the Atlantic Ocean in 1992, without refueling, at an average speed of 53.1 knots. The application of these and related technologies to fast attack craft (FAC) of 200 to 500 tonnes can result in vessels with extraordinary capabilities. The combination of 40 + knot speeds, navigational draft of less than 2 meters, enhancements for signature reduction, active and passive sensors, data linking with remote sources and 75 + tonnes for mission payload and fuel offer creative options for operation in a littoral environment.This paper describes a multi‐mission, 250‐tonne FAC, propelled by waterjets with power supplied by gas turbines and diesels. Sufficient detail is provided to indicate weight allocated for mission equipments, the weights for light ship and the loads and optional stations for launching/recovering delivery vehicles. Operational characteristics of this FAC are described such that they may be used for studying tactical advantages.

An Air-Capable Combatant For the 21st Century

During the next decade, the force structure of the U.S. Navy will be in flux, as it reacts to changing political relationships, advancing technology, and declining resources. Newly developed vertical takeoff and landing (VTOL) aircraft, such as the V-22 Osprey and AV-8B Harrier, offer the U.S. Navy an air capability for its future battle force combatants that needs to be explored. What would a battle force combatant with a detachment of six VTOL aircraft and a destroyer combatant with a detachment of six VTOL aircraft and a destroyer combat suite like the DDG-51's resemble? Can such a ship be designed within reasonable size and cost limits? A feasibility design study was conducted of alternative concepts to determine the smallest, minimum cost, lowest risk, air-capable battle force combatant capable of conducting operations in the 21st century. The paper discusses the evolution of the design, including alternative ship, hangar and elevator configurations. It also describes the development of the light ship weights and vertical centres of gravity, deck area and volume, electrical power and hull form. In addition the paper covers the process used to develop the design, including the use of advanced technologies, such as integrated electric propulsion.

THE DEEP‐ VEE HULL FORM — IMPROVES SEAKEEPING AND COMBAT SYSTEM PERFORMANCE

ABSTRACTA unique deep‐Vee hull form has been developed and model tested in Europe for use in the design of corvette and frigate sized ships. The seakeeping performance of this new deep‐Vee hull form, whose proportions are suitable for ship operations in a displacement mode at conventional speed‐to‐length ratios, exceeds the performance of ships with more conventional round‐bilge hull forms. It promises to provide a 4,500‐ton frigate with the speed, course selectivity, and combat system performance equivalent to that of larger destroyers when operating in the high latitudes of the North Atlantic, especially during the winter season.The authors describe and compare the seakeeping performance of two 4,500‐ton frigates, one with a deep‐Vee and the other with a round‐bilge hull. They discuss the impact of differences in seakeeping performance on combat system availability.From the standpoint of incorporating a deep‐Vee hull form into a ship design, certain features of a deep‐Vee hull form affect ship proportions, calm water resistance, hull structure (particularly hull girder bending moments), stability, deck area, arrangements, propulsion plant configuration, light ship weights and centers of gravity, and acquisition and life cycle costs differently than a round‐bilge hull form. Based on a comparative feasibility design study of two frigates of about 4,500‐tons, one with a deep‐Vee and the other with a round‐bilge hull, the authors quantify the impact of these differences on a ship design.

AN ANALYTICAL TREATMENT OF THE ACCURACY OF THE RESULTS OF THE INCLINING EXPERIMENT

ABSTRACTThe ability of the inclining experiment to accurately determine light ship displacement and vertical center of gravity (VCG) will be discussed and analyzed. Discussions will focus on practical considerations involved in conducting an inclining experiment without gross errors and with the highest practical and warranted precision relative to the criteria used to judge the results. The analysis will be carried out by combining the individual errors of the mutually independent measured or calculated parameters in the generalized displacement and VCG formulae. The errors on the parameters, assumed to be Gaussian distributed, are expressed as individual standard deviations, and these in turn are combined to obtain the standard deviations on displacement and VCG.The paper will compare U.S. Navy inclining procedures and the inclining procedures recommended by the U.S. Coast Guard for accuracy of resultant light ship displacement and VCG values. The errors on the independent parameters will be discussed, and a numerical example of an analysis of an actual ship inclining will be presented to demonstrate how much the deviations of the individual parameters affect the accuracy of the inclining result. The paper concludes by suggesting the magnitudes of design allowances required on displacement and VCG in order to account for the probable inaccuracy in the experimentally‐derived displacement and VCG values.

An integral approach to vibration problems of passenger-rail ferries

A rather extensive vibration analysis is described, which has been performed for a passenger-rail ferry in order to find out an acceptable solution of the vibration problem caused by installation of two independent propulsion systems, light ship stru

Factor Analysis of Coastal Air Pressure and Water Temperature

From an examination of the rotated factors produced by common factor analysis, a relationship between water temperatures measured at Blunt's Reef Light Ship and air pressure measured at Eureka, Calif., was isolated. Also water temperatures recorded at both Trinidad Head and Blunt's Reef were quite different as evidenced by differences in factor loadings. Furthermore, the magnitudes of the correlation coefficients between water temperatures and air pressure at most sites were quite small, suggesting a complex system of ocean-air interactions throughout the study area.

The Guidance Manual for Loading Great Lakes Bulk Carriers

This paper explains the need for a guidance manual for loading Great Lakes bulk carriers. The guidance manual is concerned with limiting the stillwater bending moment to the design value. Topics covered herein are the effect of stillwater bending moment on deflection, historical stillwater bending moment as a function of ship parameters, light ship weight distribution, and items commonly included in the guidance manual.

Experimental Evaluation of an Airborne Illumination System

To evaluate an airborne illumination system for night reconnaissance, two investigations were conducted, one in flight and one in the laboratory, both using scaled simulation. The in-flight investigation suggested the desirability of: (1) using an observation aircraft flying below the “light ship”; and (2) increasing the limits of permissable lateral coverage of the lights. Both hypotheses were confirmed by a scale-model laboratory experiment.