Hydrodynamics of Moonpool-Type Floaters: A Theoretical and a CFD Formulation

Moonpool-type floaters were initially proposed for applications such as artificial islands or as protecting barriers around a small area enabling work at the inner surface to be carried out in relatively calm water. In recent years, a growing interest on such structures has been noted, especially in relation to their use as heaving wave energy converters or as oscillating water column (OWC) devices for the extraction of energy from waves. Furthermore, in the offshore marine industry, several types of vessels are frequently constructed with moonpools. The present paper deals with the hydrodynamics of bottomless cylindrical bodies having vertical symmetry axis and floating in a water of finite depth. Two computation methods were implemented and compared: a theoretical approach solving analytically the corresponding diffraction problem around the moonpool floater and a computational fluid dynamics (CFD) solver, which considers the viscous effects near the sharp edges of the body (vortex shedding) as non-negligible. Two different moonpool-type configurations were examined, and some interesting phenomena were discussed concerning the viscous effects and irregularities caused by the resonance of the confined fluid.

APPLICATION OF INTERVAL TYPE-2 FUZZY SETS DEMATEL METHODS IN MARITIME TRANSPORTATION: THE CASE OF SHIP COLLISION

Accident analyse in marine industry is one of the critical issues for safety practitioners to prevent loss of life. Although considerable efforts were undertaken to prevent marine accident, numerous researches revealed that marine accidents are still on-going. In order to minimize accidents in the marine transportation, this paper presents a proactive decision- making tool which is integrating Decision-Making Trail and Evaluation Laboratory (DEMATEL) method with interval type-2 fuzzy sets (IT2FSs). As the DEMATEL enables to analyse cause and effect relationship in decision-making, the IT2FSs overcome ambiguity and vagueness of linguistic assessment of decision-makers through the DEMATEL. Thus, significant accident causal factors and their effects can be analysed on the basis of cause-effect diagram. The application of proposed approach is demonstrated with a real ship collision case. Beside its theoretical contribution, the proposed approach provides practical benefits to ship owners and operators to perceive cause and effect relationship and to avoid marine accident.

A RESEARCH ON TECHNIQUES, MODELS AND METHODS PROPOSED FOR SHIP COLLISION AVOIDANCE PATH PLANNING PROBLEM

The development of soft computing techniques in recent years has encouraged researchers to study on the path planning problem in ship collision avoidance. These techniques have widely been implemented in marine industry and technology-oriented novel solutions have been introduced. Various models, methods and techniques have been proposed to solve the mentioned path planning problem with the aim of preventing reoccurrence of the problem and thus strengthening marine safety as well as providing fuel consumption efficiency. The purpose of this study is to scrutinize the models, methods and technologies proposed to settle the path planning issue in ship collision avoidance. The study also aims to provide certain bibliometric information which develops a literature map of the related field. For this purpose, a thorough literature review has been carried out. The results of the study have pointedly showed that the artificial intelligence methods, fuzzy logic and heuristic algorithms have greatly been used by the researchers who are interested in the related field.

DEVELOPMENT OF AUTOMATIC MODE DETECTION SYSTEM BY IMPLEMENTING THE STATISTICAL ANALYSIS OF SHIP DATA TO MONITOR THE PERFORMANCE

The shipping industry depends on a global regulatory framework to operate efficiently. The industry is currently facing various technical and regulatory challenges. Performance monitoring, vessel optimisation, reduction of emissions and maintenance have become high priorities for ship operators. The marine industry is also moving towards autonomous operation to reduce human error. The rate of sensor technology implementation has increased and also raised new technological challenges. The analysis of sensor data creates new challenges to achieve operational excellence. This paper presents the implementation of statistical analysis on ship data and develops a system to automatically detect the vessel operational modes based on sensor data.

Effects of Blade Number on the Propulsion and Vortical Structures of Pre-Swirl Stator Pump-Jet Propulsors

Reducing the noise of the underwater propulsor is gaining more and more attention in the marine industry. The pump-jet propulsor (PJP) is an extraordinary innovation in marine propulsion applications. This paper inspects the effects of blade number on a pre-swirl stator pump-jet propulsor (PJP) quantitatively and qualitatively. The numerical calculations are conducted by IDDES and ELES, where the ELES is only adopted to capture the vortical structures after refining the mesh. The numerical results show good agreement with the experiment. Detailed discussions of the propulsion, the features of thrust fluctuation in time and frequency domains, and the flow field are involved. Based on the ELES results, the vortices in the PJP flow field and the interactions between the vortices of the stator, rotor, and duct are presented. Results suggest that, though changing the blade number under a constant solidity does not affect the propulsion, it has considerable effects on the thrust fluctuation of PJP. The wakes of the stator and rotor are also notably changed. Increasing the stator blade numbers has significantly weakened the high-intensity vortices in the stator wake and, hence, the interaction with the rotor wake vortices. The hub vortices highly depend upon the wake vortices of the rotor. The hub vortices are considerably broken by upstream wake vortices when the load per rotor blade is high. In summary, the blade number is also vital for the further PJP design, particularly when the main concerns are exciting force and noise performance.

Optimization of Wind Sail using Computational Fluid Dynamics Simulation

The marine industry is highly dependent on oil as the fuel and the increased consumption of this fast-depleting oil recourse creates a shortage of fuel for the future as well as pollutes the environment. The pollution of water bodies also seriously affects marine life. Thus, the need for an alternate sustainable fuel source is of great importance. One such feasible alternative energy source is wind energy. The abundance, free availability and ease of conversion make it an ideal alternative to oil. Wind energy can be extracted by wind turbines or by sails. The sails convert the wind energy directly into energy for propulsion. The challenge in the conversion is the relative angle of attack of wind on the sail. The wind cannot be expected to be always in the direction of the course of the ship. When the wind is at an angle to the direction of the course, the thrust in the course director will be reduced and a component of thrust is developed on the sail which shifts the course of the ship. Bringing the ship back to the original course will create an additional expenditure of fuel. In such circumstances modification of the sail section shape from its conventional form to an optimal form helps to reduce these deficiencies. Therefore, the effort here is to numerically analyze the aerodynamic characteristics of wing-sails and to optimize their shape. The aerofoil NACA 0018 used here was chosen through a high fidelity two-dimensional computational analysis which was done earlier. The tip of the NACA 0018 was further modified by tilting it through different angles and at different chord positions forming a flap. The main objective of the study is to optimize the angle and the position of the flap relative to the chord of the aerofoil. The flapped airfoils were formed by modifying them from 10% chord length to 60% chord length. That flap angle was also varied from 0 degrees to 50 degrees in steps of 10- deg. The angle of attack on the sail was varied from 0 to 10 degrees in steps of 2 degrees. The thrust in the direction of course and the lateral thrust of each of these sail sections were estimated, tabulated and graphs were plotted. Analyzing these, an optimum shape for the sail section is derived.

Design of a Mass Air Flow Sensor Employing Additive Manufacturing and Standard Airfoil Geometry

This work concerns the design, fabrication, and preliminary characterization of a novel sensor for determining the air intake of low and medium power internal combustion engines employed at various applications in the marine industry. The novelty of the presented sensor focuses on the fabrication process, which is based on additive manufacturing combined with PCB technology, and the design of the sensing elements housing geometry, which is derived through suitable CFD simulations and is based on standard airfoil geometry. The proposed process enables low-cost, fast fabrication, effective thermal isolation, and facile electrical interconnection to the corresponding circuitry of the sensor. For initial characterization purposes, the prototype device was integrated into a DIESEL engine testbed while a commercially available mass air flow sensor was employed as a reference; the proper functionality of the developed prototype has been validated. Key features of the proposed device are low-cost, fast on-site manufacturing of the device, robustness, and simplicity, suggesting numerous potential applications in marine engineering.

Analysis and forecast of marine economy development in China

PurposeIn recent years, China's marine industry has maintained rapid growth in general, and marine-related economic activities have continued to improve. The purpose of this research is to analyze the basic situation of China's marine economy development, identify the problems therein, forecast development trends and propose policy recommendations accordingly.Design/methodology/approachThis research conducts a comprehensive and detailed analysis of the development of China's marine economy with rich data in diversified aspects. The current situation of China's marine economy development is analyzed from the perspective of scale and structure, and the external and internal development environment of China's marine economy is discussed. With the application of measurement and prediction method such as trend extrapolation, exponential smoothing, grey forecasting and neural network method, the future situation of China's marine economy development is forecasted.FindingsIn a complex environment where uncertainties at home and abroad have increased significantly, China's marine economy development suffers tremendous downward pressure in recent years. As China has achieved major achievements in the prevention and control of the COVID-19 epidemic, the marine economy development will gradually return to normal. It is estimated that the gross marine production value in 2022 will exceed 10 trillion yuan. China's marine economy will continue to maintain a steady growth trend in the future, and its development prospects will remain promising.Originality/valueThis research explores the current situation and trends of China's marine economy development and puts forward policy recommendations to promote the steady and health development of China's marine economy accordingly.

A Numerical Assessment of the Efficacy of a Topography Design with Increasing Gradient Complexity for Filtering Biofouling Material through the Membrane Module of a Water Treatment System

Biofouling can also be defined as the micro- / macro- organisms stuck on the surface that has been submerged in water. This is normally found in marine industry and water treatment industry. There are 3 ways of antifouling where the 3rd method surface modification was the main point to be focused on. Surface modification has high potential for antifouling performance and is not harmful to the ecosystem. In this research study was to find out the efficacy of antifouling performance with increasing the gradient complexity. The 2 models used were smooth topography and circular topography and have been manipulated and simulated with WorkBench 2020, Computational Fluid Dynamic (CFD). The results were simulated with the correct meshed and models. The simulated results were converged and 2 hydrodynamic variables; velocity and wall shear were used to check the efficacy of antifouling performance.