Ship Length Research Articles

Automatic identification system data-driven model for analysis of ship domain near bridge-waters

AbstractThe ship safety domain plays a significant role in collision risk assessment. However, few studies take the practical considerations of implementing this method in the vicinity of bridge-waters into account. Therefore, historical automatic identification system data is utilised to construct and analyse ship domains considering ship–ship and ship–bridge collisions. A method for determining the closest boundary is proposed, and the boundary of the ship domain is fitted by the least squares method. The ship domains near bridge-waters are constructed as ellipse models, the characteristics of which are discussed. Novel fuzzy quaternion ship domain models are established respectively for inland ships and bridge piers, which would assist in the construction of a risk quantification model and the calculation of a grid ship collision index. A case study is carried out on the multi-bridge waterway of the Yangtze River in Wuhan, China. The results show that the size of the ship domain is highly correlated with the ship's speed and length, and analysis of collision risk can reflect the real situation near bridge-waters, which is helpful to demonstrate the application of the ship domain in quantifying the collision risk and to characterise the collision risk distribution near bridge-waters.

Application of an Artificial Neural Network and Multiple Nonlinear Regression to Estimate Container Ship Length Between Perpendiculars

Abstract Container ship length was estimated using artificial neural networks (ANN), as well as a random search based on Multiple Nonlinear Regression (MNLR). Two alternative equations were developed to estimate the length between perpendiculars based on container number and ship velocity using the aforementioned methods and an up-to-date container ship database. These equations could have practical applications during the preliminary design stage of a container ship. The application of heuristic techniques for the development of a MNLR model by variable and function randomisation leads to the automatic discovery of equation sets. It has been shown that an equation elaborated using this method, based on a random search, is more accurate and has a simpler mathematical form than an equation derived using ANN.

A method for compressing AIS trajectory data based on the adaptive-threshold Douglas-Peucker algorithm

The deficiencies of massive data like storage difficulty, computation inefficiency, and information redundancy call for ship trajectory compression. While most studies on ship trajectory compression have one or more of the following drawbacks: the drawback of low compression efficiency; the problem resulted from error ship static information when the distance threshold is set based on ship length or width; poor compression quality for some trajectories, which is caused by experience-based optimal threshold. To solve these problems, we propose the ADP (Adaptive-threshold Douglas-Peucker) algorithm based on DP (Douglas-Peucker) algorithm. By determining the key points of each trajectory through the threshold change rate, ADP no longer relies on ship static information and makes it easier to determine the threshold, which is what traditional algorithms cannot achieve. Additionally, we use the advantage of matrix operation and the method of reducing points to improve the algorithm's computation efficiency. To verify the feasibility and superiority of the proposed algorithm, we compared our algorithm with DP algorithm, Partition-DP algorithm and Sliding Window algorithm from four aspects, namely, compression rate, Synchronous Euclidean distance, Length Loss Rate and running time. The experimental results prove that our algorithm has advantages over the other three algorithms, especially in threshold setting.

Mechanical properties analysis of the naval ship similar model with an integrated sandwich composite superstructure

The research object of the article is a similar model of a naval ship with an integrated sandwich composite superstructure. The similarity model of this naval ship is based on the similarity theory, which is obtained by scaling down the actual naval ship. Based on the theoretical guidance of the double-beam method, by using the static loading test of the four-point bending method, the article analyzes the magnitude and trend of the strain, stress, and deformation of the measuring points on the naval ship model under different load cases. The main measuring points of the similar naval ship model are located in the typical cross-sections, each deck, and the interface between the steel main hull and the integrated sandwich composite superstructure. The article mainly explores the changes of longitudinal strain and stress of the measuring points with height on three typical cross-sections, and the changes of longitudinal strain and stress with the ship's length on the interface, and the deformation of the top deck of the superstructure. Combining with the results of finite element numerical simulation, the complicated mechanical properties of the naval ship model with an integrated sandwich composite superstructure are explored by mutual verification with the experiments. Some valuable conclusions are obtained for the construction and design of the naval ship with an integrated sandwich composite superstructure.

Investigation of Non-Linear Ship Hydroelasticity by CFD-FEM Coupling Method

With the increase of ship size, the stiffness of the hull structure becomes smaller. This means that the frequency of wave excitation tends to be closer to the natural frequency of the hull vibration, which in turn makes the hydroelastic responses more significant. An accurate assessment of the wave loads and motion responses of hulls is the key to ship design and safety assessment. In this paper, the coupled CFD (Computational Fluid Dynamics)-FEM (Finite Element Method) method is used to investigate the non-linear hydroelasticity effect of a 6750-TEU (Twenty-foot Equivalent Unit) container ship. First, by comparing the heave, pitch, and vertical bending moment at midship section (VBM4) against experimental results reported in the literature, the validity of the numerical method in this paper is illustrated. Secondly, the ship responses under different wave length–ship length ratio, wave frequency-structure natural frequency, wave steepness, and ship speeds are studied. It is found that the wave length–ship length ratio has a more important influence on the hydroelastic response than that from wave frequency-structure natural frequency ratio, and the effect of wave non-linearity will behave differently under different wave length–ship length ratio. The increase of rigid body motion caused by forward speed will not correspondingly increase the non-linearity of the hydroelastic response.

Application of fault tree analysis in LNG fire risk assessment of LNG fueled ships

Assess the risk of LNG fire of LNG fueled ships navigating in the middle reaches of Yangtze River of China according to the acceptable risk criteria so that support technically to design, building and shipping safety management of LNG fueled ships and also to marine safety administration. “Fault tree analysis” was used to analyze the contribution of factors for LNG fire of LNG fueled ships. Statistical analysis base on the Normal distribution was carried out to reveal the confidence intervals of the probability of ships collision, touch and general fire. Quantitative assessment showed that LNG fuel is not suitable for passenger ships and chemical cargo carriers. It was found that ship length is the key to people onboard evacuating in case of LNG fire, so that LNG valid volume above 20M3 was unsuitable for a ship with length less than 80 m as well as that more than 10M3 was very dangerous for crew onboard a ship with length less than 45 m. Factors of bridges over river, berths along banks and anchorages in river, which would aggravate the consequences of LNG fire, were taken into consideration during risk assessment. In view of navigation condition in the middle reaches of Yangtze River, measures were suggested for LNG fire risk control of LNG fueled ships.

Experimental and Theoretical Study of the Effect of Hull Roughness on Ship Resistance

Hull roughness increases ship frictional resistance and, thus, results in economic and environmental penalties. Its effect has been prevalently predicted using the similarity law scaling procedure. However, this method has not yet been validated with experimental data using a model ship. This study presents an experimental investigation into the effect of roughness on ship resistance and provides a validation of the similarity law scaling, by using tank testing of a flat plate and a model ship. Both the plate and the ship were tested in smooth and rough surface conditions, respectively. For the rough surface conditions, sand grit (aluminum oxide abrasive powder) was applied on the surfaces of the flat plate and the ship model. The roughness functions of the rough surface were derived by using the results obtained from the flat plate tests. Using the roughness function and the flat plate towing test, frictional resistance was extrapolated to the length of the model ship following the similarity law scaling procedure. The total resistance of the rough ship model was first predicted using the extrapolated frictional resistance and the result of the smooth ship model, and then compared with the results from the rough ship model. The predicted total resistance coefficients for the rough ship model showed a good agreement with the measured total resistance coefficient of the rough ship model, thus proving the validity of using Granville’s similarity law scaling to extrapolate the roughness effect on ship resistance.

Dynamic model of cable tension and configuration for vessel at anchor

A numerical model considering the seabed friction is developed to investigate the dynamic behavior of anchor cable in this paper. In the model, the anchor cable was divided into hanging and lying parts. The governing equations of hanging and lying anchor cables were established respectively based on finite difference method and coupled according to the boundary conditions. The coupled equations of anchor cable were solved by Newton iteration and the static anchor cable parameters used for the initial values were confirmed by double bisection method. To illustrate the reasonability and validity of the model, several simulations of vessel sway in wind with different time and space step sizes and different seabed friction coefficients were presented. The simulation results show that anchor cable snap load is 3–5 times of average tension, the variation of anchor cable bearing is 2 times of ship heading, and the sway amplitude of the ship’s center of gravity is about one times of ship length. Compared with the experimental data, the model and algorithm in this paper can successfully provide the realistic prediction of the dynamic tension and configuration of anchor cable, and can be used as a reference for anchoring operation. Farther, this paper found out that the normal seabed friction coefficient has considerable impact on the cable tension.

Material Effectiveness Model for the Construction of Aluminum Hull

Construction of a hull generally requires several plates and profile material. Early indications for shipbuilding indicate that in manner, the linear function approach for installed material was 75% to 90%, and waste material was 10% to 25%. This study is conducting an assessment of the area of installed material and waste material on small vessels made of aluminum with variations in ship length and the method of approach trend lines both linear and nonlinear. Secondary data retrieval in the form of an aluminum cutting plan for plate material and profile from the AutoCAD application, which is then reprocessed through the FastCAM application to obtain results in the form of identification of installed material and waste material area. Based on variations in ship length and material area results, a scatter plot process was carried out through the Excel application to obtain results in the form of trend line functions with an R-squared determination coefficient of more than 0.9 and the results of the calculation of the intersection between the function of installed material and waste material, and the waste material function with the x-axis uses the balance method. The final result showed that the linear function gives an indication of the effectiveness of the material located in the range of 6 to 23 meters in length of the boat and polynomial function of order 2 in the range of 6 to 18 meters in length, while the waste material area in the two functions maximum 22%.

Unmanned surface vehicle track control based on improved LOS and ADRC

Objectives Under complex environmental conditions, unmanned surface vehicles (USVs) may deviate from the target course. In order to improve the anti-jamming ability and actual navigation stability, and achieve accurate track control, an improved USV track control method is proposed. Methods According to the influence on navigation signals caused by the environment, track control is analyzed in two cases of GPS signal: effective and invalid. A track control method based on a fuzzy control variable ship length ratio line-of-sight (LOS) algorithm and active disturbance rejection control (ADRC) algorithm is then realized on an autonomous controllable platform, and a lake test is carried out using a USV with dual propellers and dual rudders. Results The simulation results show that this method can meet the requirements of track control, and the heading can be stabilized quickly without frequent rudder swinging after turning. The proposed method can complete track control in real environments with an average track error of about 0.1 m and variance of about 0.03. Conclusions The lake test results verify the feasibility and effectiveness of the proposed algorithm in practical engineering applications.

A Detailed Identification of Classificatory Variables in Ship Accidents: A Spanish Case Study

The present paper shows an original study of more than 163 ship accidents in Spain showing which of the usually employed variables are related to each type of vessel accident due to the lack of information in this region. To this end, research was carried out based on the Spanish Commission for Investigation of Maritime Accidents and Incidents (CIAIM) reports. Detailed combinatory ANOVA analysis and Bayesian networks results showed a good agreement with studies of other regions but with some particularities per each type of accident analyzed. In particular, ship length was defined as the more relevant variable at the time to differentiate types of accidents. At the same time, both the year of build and the fact that the ship meets the minimum crew members required were excellent variables to model ship accidents. Despite this, the particularities of the Spanish Search and Rescue (SAR) region were defined at the time to identify accidents. In this sense, although variables like visibility and sea conditions were employed in different previous studies as variables related to accidents occurrences, they were the worst variables to define accidents for this region. Finally, different models to relate variables were obtained being the base of deterministic dynamic analysis. Furthermore, to improve the accuracy of the developed work some indications were obtained; revision of CIAIM accidents scales, identification of redundant variables, and the need for an agreement at the time to define the classification limits of each identification variable.

DESAIN DAN PERHITUNGAN BODY KAPAL ATAU HULL STRUCTURE PEMBERSIH SAMPAH DI PANTAI

This garbage cleaning ship is a new building design that functions as a garbage cleaning beach with a size of a ship length of 12, 4m wide and 2m high. The design of this garbage cleaning vessel is a solution to help cleaning and transporting waste along the coast in general in accordance with the Karimun district government program.
 Based on the results of calculations on the construction design of the garbage cleaning vessel body, the body or hull of the garbage cleaning vessel, weighs 19,766 tons and is designed to lift ± 20 tons of wet garbage. This garbage cleaning vessel has a height of 0.401 m empty ship and is loaded with a load of 0.800 m. For the design of the thickness of the plate on the Deck Plate, Shell Plate and bottom plate from the calculation found the thickness of the plate 8 mm and for the transverse stability value of the ship the value of KM 2.86 m, KG 1 m, KB 0.2 m while the stability value extends the ship KM value 24 m, KG 1 m, KB 0.2 m.

Neural network integration in the analysis, selection of wageningen’s b-series ship propeller

In the preliminary stage, ship design analyzes and evaluates the close correlation and interaction fit between the hull, main engine, and propulsion. Therefore, the process of calculation and selection of the appropriate propulsion device plays the role of ensuring the necessary propulsion to achieve the design speed according to the mission and ensuring the appropriate torque of the main engine to achieve optimal performance. According to the traditional approach, the propeller design method is based on series B - Wageningen's experimental graph to determine the suitable diameter and geometric parameters. This paper presents the method of integrating the neural network algorithm in the preliminary design stage to support selecting the appropriate blade area ratio from input parameters, including the ship length, displacement, design speed, and the number of propeller blades. The neural network principle is to synthesize the reference result from the propeller database's individuals to give the appropriate blade area ratio with the closest probability in the database, taking into account cavitation. In this study, the B-Wagenningen series propeller design database is verified and applied well in practice. On that basis, the propeller geometry parameters are proposed from the neural network algorithm, and the thrust and torque coefficients are calculated and verified based on computational analysis from commercial software.

Model experiment of large superstructures’ influence on hull girder ultimate strength for cruise ships

Cruise ships have large and long superstructures, which are almost extending the whole ship length with discontinuous characteristics, such as side shell recess and many window openings. The superstructure effectiveness on hull girder longitudinal strength is a complicated but unavoidable issue in ship design stage. This paper has carried out a collapse experiment of steel model with superstructures, which is designed based on one actual cruise ship. Critical factors including initial imperfections and welding residual stress used in nonlinear FE analysis have been validated by the experiment results. Then, the superstructure effectiveness is analyzed to revise the increment-iterative to be applicable for ultimate strength evaluation for cruise ships. At last the combination action of bending moment and shear force is studied, and a new combination formula is proposed. The conclusions in this paper will be useful for ship design, rules amendment and safety assessment for cruise ships.

Nonlinear Feedback-Based Path Following Control for Underactuated Ships via an Improved Compound Line-of-Sight Guidance

To promise the high fidelity of path following control for the underactuated ship from the aspect of the nautical practice, this paper develops a nonlinear feedback-based control scheme with an improved compound line-of-sight (ICLOS) guidance law, which has the energy-saving and efficient performance. Based on the methodology of the nonlinear disturbance observer and method of reduced-order extended state observer (ESO), a reduced-order state nonlinear sideslip angle observer is developed for online estimation of the time-varying sideslip angel caused by external disturbances, and a sideslip angle controller is incorporated to avert the sharp acting of actuators. Meanwhile, unlike the traditional line-of-sight (LOS) guidance law, a time-varying lookahead distance is designed as a function that relates to the ship' cruising speed and the cross track error, while the advance steering distance is also variable responding to the ship's length and turning angle, both of them make the turning process smoother. In the control scheme, the second-order closed-loop gain shaping algorithm (CGSA) is employed to design a concise robust controller, where the fuzzy logic system (FLS) is introduced to adjust the integral coefficient online to improve the transient performance. In addition, to further reduce the steering frequency and energy consumption of the system, nonlinear feedback technology (NFT) is adopted. Numerical simulation and comprehensive comparisons are conducted to demonstrate the remarkable performance and superiority of the proposed path following control system.

Preliminary Study of Ship Maneuvering Prediction of Container Ship

Ship maneuvering is defined as the inherent capability of a vessel to turn its path based on the hydrodynamics principles. The maneuvering performance becomes important to the safety of navigation when a ship operates. In case of vessel turning motion, International Maritime Organization (IMO) requires the maximum tactical diameter is five times of the ship lengths. Tactical diameter is the distance travelled by the ship’s center of gravity in a parallel direction to the ship’s initial path. In this paper, semi-empirical approach proposed by Clarke (1983) was used to obtain the first derivative of hydrodynamics equation. After that, the maneuvering performance was calculated using Son and Nomoto’s mathematical model (1981). Based on IMO regulations, the calculation of tactical diameter was conducted with 35° of rudder position. The calculation and analysis of tactical diameter was carried out according to relevant procedure of the ship maneuvering provided by IMO. The calculation result shows satisfactory result based on IMO regulations. The maximum tactical diameter does not exceed the requirements of IMO maneuvering standards. A further investigation was performed to see whether there was any impact on ship’s main dimensions to the maneuverability performance. In the future study, the development of open source software program to analyze the ship maneuvering performance is considered. It is expected to be able to contribute for facilitating in the preliminary ship design process.

Experimental and Numerical Investigation of Green Water Occurrence for KRISO Container Ship

The occurrence of green water on the deck of Korea Research Institute of Ships & Ocean Engineering (KRISO) container ship is investigated using model test experiments and a fully coupled impulse response function (IRF)–computational fluid dynamics (CFD)–based numerical approach. In the experimental study, green water pressure over the deck and superstructure is investigated for different regular head wave conditions (wavelength/ship length ratio: .8–1.5) and vessel speeds (Froude number: .055–.166). The impact pressure on the deck is found to be highest at a wavelength/ ship length ratio of 1.2 and increases drastically with the increase in Froude number. The variation of green water pressure with wave steepness is linear for points on the forward deck and quadratic for the superstructure. In the second part, a coupled IRF-CFD–based numerical method is developed in which the global hydrodynamic forces such as radiation–diffraction and Froude–Krylov force are computed using a potential flow solver, whereas the local pressure due to the shipping water impact is computed using CFD and added as an external force. Comparisons of vessel motions and green water pressures with experiments indicate that the coupled IRF-CFD method can be a robust and efficient tool to predict shipping water loads on ships. Introduction The prediction of green water shipped on the deck and the resulting impact on ships and offshore structures have been an important research topic in the last couple of decades because it is directly related to the safety of the structure at sea. Historically, shipping of water on the deck had caused many serious damages to the bow and superstructure, and some of them have even capsized; e.g., the Schiehallion Floating Production Storage and Offloading (FPSO) was damaged severely in November 1998 because of steep waves. These incidents resulted in considerable research on this topic in the past two decades. The primary focus has been on the understanding of critical aspects and the accurate prediction of green water loading which requires proper modeling of green water occurrence. Also, accurate calculation of the green water loads on the deck and superstructure is very important for structural design load calculation. However, this is a nontrivial task because it depends on many physical and geometrical factors such as wave steepness, the wavelength- to-ship length ratio, hull shape around the bow region, and vessel speed. Hence, efforts have been made to develop suitable numerical models that may consider most of these aspects under necessary underlying assumptions.

Effective ship domain – Impact of ship size and speed

The ship domain is a concept commonly proposed as a safety assessment criterion in planning collision avoidance manoeuvres of a ship or its safe route. The work presents authors’ methods for determining an effective ship domain based on tests using Electronic Chart Display and Information System (ECDIS) simulator. The tests were conducted on non-autonomous real time models of ships steered by expert navigators. Domains were determined for ships of different sizes and speeds. The ship domain was approximated to an ellipse. The study covered absolute and relative domains, the latter defined in ship length units. The dependence of the domain shape and size on ship size and speed has been analysed and described. The formulated analytical relationships enable us to determine the domain of a ship varying in size and speed.

Detection of NO2 pollution plumes from individual ships with the TROPOMI/S5P satellite sensor

This paper presents an analysis of tropospheric NO2 column measurements from the TROPOspheric Monitoring Instrument onboard the Copernicus Sentinel 5 Precursor satellite (TROPOMI/S5P) for an oceanic area in the central Mediterranean on 2 July 2018. The day and area were selected because of the stable and cloud-free weather conditions with low wind speeds throughout most of the area, while covering one of the busiest worldwide international shipping corridors. In addition, the area was affected by sunglint, i.e. sunlight that is directly reflected by the ocean surface waves to the satellite which greatly enhances the signal-to-noise ratio of the satellite observations. The satellite measurements reveal plume-like emission structures in tropospheric NO2 columns while automated identification signal (AIS) data of ship locations reveal a total of 185 ships in the area. Combined with information about wind speed and wind direction within 3 h prior to the TROPOMI/S5P overpass, the ship tracks can almost perfectly be aligned with the plume-like tropospheric NO2 structures. In addition, information about ship length and ship speed, combined with an analysis of ship tracks and ship position, reveal that nearly all emission plume-like tropospheric NO2 structures can be attributed to the largest ships, mostly container ships and crude oil tankers. Overall, our results show for the first time ever that NO2 emission plumes from ships can be detected and attributed to individual ships using satellite measurements, while also providing strong support for using satellite sunglint measurements.

P.845The effect of antipsychotic therapy on the social functioning of patients with paranoid schizophrenia

A ship encounters wave loads in actual seas, it is necessary to estimate the ship's manoeuvring performance in waves for its safe operations. In this study, turning characteristics of a KCS model ship in regular waves were investigated by free-running model tests. 35° port and starboard turning circle tests in regular waves were carried out in KRISO Ocean Engineering Basin with variations of regular wave heights, lengths, directions and model approach speeds. Propeller revolution rate was mostly fixed at the constant value corresponding to the full-scale speed of 16 knots in calm water. Ship's turning behaviours in waves can be divided into initial and steady turn phases. Firstly, during initial turns, the ship's safety which is related to avoiding a fixed front obstacle is focused on. ‘DMINw’ is defined as the minimum distance between the fixed front obstacle and the ship initial trajectory. And safety index ‘STw’ is proposed, which is formulated by using the ratio between DMINw in calm water and in waves. The ship becomes safer in head waves than calm water due to small advances. In starboard beam waves, when the ship turns to starboard, that becomes dangerous due to small transfers. In port beam waves, the ship which turns to starboard is mostly safe. But, in short port beam waves, yaw angle is slowly increased and the advance is relatively large. It is hypothesized that the wave drift yaw moments prevent the ship from turning to starboard. Secondly, drifting distances and angles in steady turns are quantified. The drifting distances increase with decreasing wave lengths, when the wave lengths are varied from 0.5 to 1.0 ship length. The drifting distances are approximately proportional to the wave steepness. Finally, approximate formula of STw is proposed. That is formulated as the function of ship advance and transfer in calm water and waves only. DMINw can be simply obtained if the initial trajectory is approximated as the ellipsoidal quadrant. Based on several parametric simulations, it was confirmed that STw is proportional to the cube of the transfer in waves and is inversely proportional to the advance in waves. STw is formulated so that it can be applied to arbitrary ships.