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  • Articles  (948)
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  • Wiley-Blackwell  (859)
  • De Gruyter  (89)
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  • 2020-2022  (89)
  • 1970-1974  (859)
  • Technology  (948)
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  • Articles  (948)
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  • 1
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    Towards Improving Optimised Ship Weather Routing (2020)
    De Gruyter
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    Publication Date: 2020-03-01
    Description: The aim of the paper is to outline a project focussing on the development of a new type of ship weather routing solution with improved uncertainty handling, through better estimation of ship performance and responses to sea conditions. Ensemble forecasting is considered to take into account the uncertainty levels that are typical of operations in a stochastic environment. Increased accuracy of weather prediction is achieved through the assimilation of real-time data, measured by an on-board monitoring system. The proposed system will allow smooth integration of short-term Decision Support Systems for ship handling in dangerous or peculiar situations with long-term Decision Support Systems for weather routing. An appropriate user interface is also a critical part of the project and it will be implemented in a commercial Electronic Nautical Chart environment. A prototype of the full system will be installed and tested on a commercial vessel in regular operations and under real environmental conditions.
    Print ISSN: 1233-2585
    Electronic ISSN: 2083-7429
    Topics: Technology , Economics
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  • 2
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    Determining the Best Possible Speed of the Ship in Shallow Waters Estimated Based on the Adopted Model for Calculation of the Ship’s Domain Depth (2020)
    De Gruyter
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    Publication Date: 2020-09-01
    Description: The purpose and scope of this article is to present the best marine practices used to determine the ship’s domain depth (compared to the safety depth parameter in ECDIS) and the safest and best possible speed (also known as optimal speed) of the ship in restricted sea areas limited by the depth of navigation waters. The author also presents a method that can be used to estimate the safe speed of a ship in shallow waters and the so-called navigational risk factor (specified in the range from 0 to 1), using the safety depth parameter specified in ECDIS based on the analysis of a three-dimensional model of the ship’s domain. The essence of the method proposed in this paper is a systematic approach to the operation of a seagoing ship in the aspect of assessing its navigation safety (navigational risk factor) when manoeuvring in restricted sea areas, in particular in shallow waters including navigable canals and fairways.
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    Electronic ISSN: 2083-7429
    Topics: Technology , Economics
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  • 3
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    Analysis of Ultimate Compressive Strength of Cracked Plates with the Use of DoE Techniques (2020)
    De Gruyter
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    Publication Date: 2020-09-01
    Description: The objective of this work is to investigate the structural compressive response of plates with locked cracks accounting for all relevant factors and correlation between them. The nonlinear FE model considering both geometric and material nonlinearities is employed herein, and the FE model of the structural response of intact plates is validated with the available experimental data. In the common studies, based on One Factor at a Time analysis, some of the parameters and interactions between them are excluded. In the present study, the numerical investigations are conducted with the use of the Design of Experiments techniques, where all essential parameters and their interactions are adequately considered. With a total of 32 numerical analyses, the most influential factors and their interactions are identified. As a study outcome, empirical formulations, which allow for a fast estimation of the ultimate compressive strength of intact plates, plates with locked cracks, and repaired cracked plates, are derived. The developed formulations represent a fast and practical tool for estimating the ultimate compressive strength of intact, cracked, and repaired plates, which can be easily employed in the reliability analysis.results followed by their discussion.
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    Electronic ISSN: 2083-7429
    Topics: Technology , Economics
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  • 4
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    Short Review and 3-D FEM Analysis of Basic Types of Foundation for Offshore Wind Turbines (2020)
    De Gruyter
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    Publication Date: 2020-09-01
    Description: Some problems of the foundations of offshore wind turbines are considered in this paper. A short review is presented on the two basic types of foundations, i.e. monopiles and gravity foundations, including their basic features and applications as well as general design considerations. Also, some issues regarding analysis are discussed, including geotechnical problems and modelling techniques. A numerical model of offshores turbine and some preliminary computations are presented. Finite element analysis was carried out for wind turbines supported on both gravity and monopile foundations. The wind turbine tower, blades (simplified model), gravity foundation and part of the surrounding soil are included in the model. The turbine was loaded by wind and loads induced by waves, inertia and gravity. Both non-linear static and dynamic analysis of the wind turbine was performed. The displacements and stresses under the tower foundations were calculated and a comparison analysis carried out.
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    Electronic ISSN: 2083-7429
    Topics: Technology , Economics
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  • 5
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    Multi-Criteria Optimisation of Multi-Stage Positional Game of Vessels (2020)
    De Gruyter
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    Publication Date: 2020-03-01
    Description: The paper presents a mathematical model of a positional game of the safe control of a vessel in collision situations at sea, containing a description of control, state variables and state constraints as well as sets of acceptable ship strategies, as a multi-criteria optimisation task. The three possible tasks of multi-criteria optimisation were formulated in the form of non-cooperative and cooperative multi-stage positional games as well as optimal non-game controls. The multi-criteria control algorithms corresponding to these tasks were subjected to computer simulation in Matlab/Simulink software based on the example of the real navigational situation of the passing of one’s own vessel with eighteen objects encountered in the North Sea.
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    Electronic ISSN: 2083-7429
    Topics: Technology , Economics
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  • 6
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    Calculation of the Dynamic Characteristics of Ship’s Aft Stern Tube Bearing Considering Journal Deflection (2020)
    De Gruyter
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    Publication Date: 2020-03-01
    Description: Dynamic properties are vital for the working reliability of aft stern tube bearings. However, the determination of such properties currently involves several simplifications and assumptions. To obtain its dynamic characteristics accurately, the aft stern tube bearing was divided into several bearing segments. The oil film reaction force was considered in the calculation of shaft alignment, and the journal deflection and actual oil film thickness were obtained accordingly. Subsequently, the perturbed Reynolds equation was solved using the finite difference method when the dynamic characteristics of journal bearings with finite width were evaluated. Then, a calculation program was developed and verified by comparing with the results of other studies. Finally, the dynamic characteristics were calculated under different revolutions. The results showed that the stiffness at the vertical direction of the aft stern tube bearing was several times that of the horizontal direction and varied with the revolutions of the shafting system. These findings can provide the foundation for the precise calculation of the journal trajectory under dynamic conditions, as well as for the evaluation of the oil film thickness. Moreover, the results led to favorable conditions for the accurate calculation of the shafting whirling vibration.
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    Electronic ISSN: 2083-7429
    Topics: Technology , Economics
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  • 7
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    Underwater Navigation System Based on Doppler Shift – Measurements and Error Estimations (2020)
    De Gruyter
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    Publication Date: 2020-03-01
    Description: A new acoustic navigation system was developed to determine the position and speed of moving underwater objects such as divers and underwater vehicles. The path of an object and its speed were determined by the Doppler shifts of acoustic signals emitted by a transmitter placed on the object and received by four hydrophones installed at the periphery of the monitored body of water. The position and speed measurements were affected by errors mainly caused by acoustic reflections (returns) from the water body boundaries and surface reverberations. This paper discusses the source of the disturbances with the results of a simulation test and experimental measurements. It was demonstrated that the magnitude of the errors could be acceptable in most of the potential applications of the acoustic navigation system.
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    Topics: Technology , Economics
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  • 8
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    Propeller Hydrodynamic Characteristics in Oblique Flow by Unsteady Ranse Solver (2020)
    De Gruyter
    Details
    Publication Date: 2020-03-01
    Description: Propellers may encounter oblique flow during operation in off-design conditions. Study of this issue is important from the design and ship performance points of view. On the other hand, a propeller operating in oblique flow may sometimes result in a better propulsion efficiency. The main goal of the present study is to provide an insight on the propeller characteristics in the oblique flow condition. In this research, the performance of the DTMB 4419 propeller is studied by the numerical method based on solving Reynolds Averaged Navier–Stokes (RANS) equations in several inflow angles. The sliding mesh approach is used to model the rotary motion of the propeller. Initially, the numerical method is verified by grid and time step dependency analysis at various inflow angles. Additionally, computed results at zero inflow angle are compared with the available experimental data and good agreement is achieved. Finally, the forces and moments acting on the propeller are obtained for 0° to 30° inflow angles. It is concluded that the inflow angle up to 10° has no significant influence on the thrust and torque coefficients as well as the propeller efficiency. However, at high angles up to 30°, the thrust and torque coefficients increase as the inflow angle increases, which may result in a significant improvement of propeller efficiency.
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    Topics: Technology , Economics
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  • 9
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    Neural Network Ensemble Approach to Pushed Convoys Dispatching Problems (2020)
    De Gruyter
    Details
    Publication Date: 2020-03-01
    Description: This paper investigates the use of neural networks (NNs) for the problem of assigning push boats to barge convoys in inland waterway transportation (IWT). Push boat–barge convoy assignmentsare part of the daily decision-making process done by dispatchers in IWT companiesforwhich a decision support tool does not exist. The aim of this paper is to develop a Neural Network Ensemble (NNE) model that will be able to assist in push boat–barge convoy assignments based on the push boat power.The primary objective of this paper is to derive an NNE model for calculation of push boat Shaft Powers (SHPs) by using less than 100% of the experimental data available. The NNE model is applied to a real-world case of more than one shipping company from the Republic of Serbia, which is encountered on the Danube River. The solution obtained from the NNE model is compared toreal-world full-scale speed/power measurements carried out on Serbian push boats, as well as with the results obtained from the previous NNE model. It is found that the model is highly accurate, with scope for further improvements.
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    Topics: Technology , Economics
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  • 10
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    Application of Shape Memory Alloys in Pipeline Couplings for Shipbuilding (2020)
    De Gruyter
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    Publication Date: 2020-09-01
    Description: The aim of the study is to analyse shape memory alloy (SMA) pipeline joints in limited space applications for all kinds of ships. Generally, the space available in various areas on ships is strictly limited and service works usually meet many obstacles. If we consider a pipeline, the flange joints always require a larger free space around the pipe than the pipe alone. A simultaneous problem can occur with the propeller shaft line coupling between bearings. SMA couplings require less space around the pipe and service should be easier, e.g., insulation fixing, painting and so on. SMA couplings last for a lifetime and there is no need for periodical seal replacement. Herein, some proposals among other unpublished data are discussed. There is a significant technological interest in the use of SMAs for applications not widely used yet. A wide variety of alloys present the shape memory effect and many generate an expressive restitution force considerable for commercial interests.
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    Topics: Technology , Economics
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