Higher Order Wave Excitation Forces and Station-Keeping Capability of A Semisubmersible

A floating body like a semisubmersible in regular or irregular waves experiences first-order and second-order wave excitation forces due to potential flow effects (radiation-diffraction theory). However, for a slender structure like columns of a semisubmersible, higher-order forces originate due to viscous effects, resulting in mean and slowly varying forces much higher than those calculated by potential flow effects. Such a significant difference may severely underestimate the wave excitation force calculation while dealing with mooring analysis or dynamic positioning (DP) capability of a semisubmersible regarding station-keeping capability. Experimental works have shown that regular waves have a much higher-order wave excitation force (cubic). This force is much higher than second-order wave excitation forces (potential flow effects) while dealing with the mean/steady drift force. Two different diameter model cylinders have proved it well. The theoretical part has also been established while dealing with the viscous drag term up to its instantaneous wave elevation. Experiments were also done for the pontoons of a semisubmersible. These experimental works resulted in an engineering rationale formula introducing a mean drag coefficient dependent on the Keulegan-Carpenter (KC) number. Further demonstration with currents has proved that these drift forces enhance considerably with the presence of currents with waves. As the natural sea is irregular, experiments with a floating semisubmersible have proven that, like the higher-order drift force, the slowly varying (low-frequency) force also increases due to viscous effects. The experimental results with cylinders and pontoons prove that second-order forces due to potential flow effects are insufficient. The viscous effects cause both mean and slowly varying forces to be considerably larger in waves and currents and waves. As a result of these variations in computation techniques, only dealing with potential flow effects may seriously underestimate the wave excitation forces while carrying out both mooring and dynamic positioning (DP) capability analysis of a semisubmersible. So, having a sufficient design safety margin, especially in storm conditions when wave frequencies are extremely low and wave heights are high, will be attractive for viscous effects to dominate both the mean and slowly varying forces. Experimental works have well-established the viscous effects in wave excitation forces (higher-order). There has also been theoretical development for engineering solutions in waves and currents. Both mean, and slowly varying forces are essential in the mooring and DP capability of a slender-body structure like a semisubmersible. Thus, additional sources due to viscous effects resulting in higher-order forces should be addressed, especially safeguarding the floater for storm conditions\u27 safety. These novel findings are equally applicable to new floating solutions for wind turbine floaters, which are very slender structures. So, wave excitation forces’ analysis without taking viscous effects may also underestimate the mooring and dynamic positioing analyses

Analysis of Drydock Use in Ship Repairing

Drydocking a ship is essential to the routine maintenance process during its service/operational life. During the drydocking time, various surveys/inspections are carried out per requirements of the classification society, flag administration, and statutory bodies, particularly the underwater items. For shipyards, optimum utilization of drydock capacity (deadweight) is the most considered factor to optimize the physical performance indicators like drydock occupancy rate, capacity utilization rate, and drydock utilization. However, in real life, even after mobilizing all available resources to achieve the optimum usage rate, the overall physical performance could be higher or lower or not up to the expectation. The average size (deadweight) of ships calling to the drydock is observed to be far below the expected capacity, resulting in under-utilization of installed capacity. However, although the drydock occupancy rate is satisfactory, even 100%. For a substantial amount of time, the drydock has been under-utilized in terms of capacity utilization and drydock utilization rate. Drydocking activities of ships in two (2) drydocks of a shipyard are collected and analyzed. Various physical performance indicators (PPIs) are calculated. They are diagnosed year-wise and presented in tabular and graphical form to demonstrate their behavior over the operating period. Authors have investigated the behavior of the above-mentioned physical performance indicators to justify, technically, the selection of capacity of a drydock. A further attempt has been made to propose some recommendations and guidelines from technical viewpoints for the selection criteria of a drydock capacity based on available resources

Global Reporting Initiative; Sustainability Reporting

Sustainability and Corporate Governance are becoming significantly important criteria for globalinvestors and capital market. Such issues are increasingly impacting investor decision. Sustainabilityreporting also helps organizations to assess their Operations v/s Sustainability issues. This in turn willhelp organizations to establish sustainable goals, measure and improve their ‘sustainability’performance and be more acceptable to Government, Society and interested parties.Stock Exchanges as a focal point for investors, have received a number of questions frominvestors relating to Sustainability practices. Exchanges are now driving and promoting Sustainabilityby encouraging businesses to adopt sustainable development reporting policies and practices

Case Studies of Single Nitrogen Expander Liquefaction for FLNG

Nowadays, global carbon dioxide emissions into the atmosphere have reached a historically high level due to carbon dioxide emissions. The current effort to change the alternative energy source of LNG fuel was found to be one of the cleanest fossil fuels due to lower carbon emissions to ease the rapid growth of carbon emissions. LNG marine industry forecasts that the increasing demand for FLNG vessels will accelerate the development of gas resources, research work on the system process analysis and optimisation of the Liquefaction system. The rapid growth in equipment and processes of FLNG development is the response to the challenges due to weight and space limits. One of the critical objectives onboard FLNG is to build the combined plant models of clean energy. The research boundary covers processes of LNG liquefaction, nitrogen separation and boil-off gas handling. BOG re-liquefaction will be used as a fuel gas supply system. BOG will also be converted to clean energy fuel such as hydrogen or ammonia for the main and auxiliary engines onboard. A small-scale liquefaction process with a refrigerant cycle is proposed in this study to meet these FLNG challenges. The Brayton refrigeration (BR) cycle is found to be most suitable for FLNG vessels, among other refrigerant cycles. The BR cycle using nitrogen as a refrigerant and a single expander is the focus of this study [8]

Evaluation of Validity and Reliability of Rapid Upper Limb Assessment (RULA) Method in Research Experiment: A Systematic Review

This research paper presents an evaluation of the validity and reliability of the Rapid Upper Limb Assessment (RULA) method used in research, examination, and experiment. A systematic review process is adopted in this evaluation approach. A range of scientific journals in which the RULA method is adopted in their respective research fields are selected for the systematic review and evaluation of the RULA method’s validity and reliability. The RULA method is used in the research area for the assessment of ergonomic risk levels using a defined evaluation scoring method with regard to different body postures adopted whilst working or performing specific tasks. It is essential to systematically evaluate and examine the RULA method of assessment in the field of ergonomic study to ascertain its validity and reliability performance. In many research areas, ensuring validity and reliability are critical parameters concerning the research methodology used, the test criteria, the hypotheses development, the assessment tools used and also the data collected and evaluated. Thus, in the research area where the RULA method is adopted, it is primarily crucial to ensure that validity and reliability are upheld and achieved. Discussion of the test of validity and reliability is also pursued in this research paper to encompass the holistic evaluation of the RULA method. Finally, the final judgement is made by proving the hypothesis whether the RULA method is valid and reliable for use in research and evaluation. The scoring of risk levels will be determined and concluded

Conceptual Analysis of Lower Back Pain Resulting from Awkward Sitting Posture in Driver Vehicle Seat—Systematic Review and Surveys

This research paper presents an analysis of the different kinds of pains in particular lower back pain (LBP) which result from the awkward sitting position of the driver. The analysis is conducted through library research and respondents\u27 field surveys. The research methodology adopted is content analysis with systematic reviews of relevant related scientific journals since the research study is from the conceptual approach. In addition, the data from the surveys will also be used to strengthen the justification of this research outcome and its hypothesis. The objective of this research paper is to identify the various main types of pain suffered by drivers resulting from sitting in an awkward posture in the car seat either during driving or stationary mode, with the ultimate aim of determining the most dominant and prevalent pain, namely low back pain (LBP) in relation to the sitting postures of drivers With this research knowledge content, it can help develop measures for the transport car manufacturing industries and policymakers for the drivingindustry to reduce ergonomic risk of low back pain (LBP)

A study on the financial feasibility of compliant ship recycling yards in Bangladesh

\ua9 2023 ANAME Publication.Ship recycling is one of the most promising industries for Bangladesh. A significant amount of local steel demand is fulfilled by scrap metals from ship recycling yards. Bangladesh has been maintaining a competitive position in the ship recycling sector along with China, India, and Pakistan. But, in the absence of substantial workplace safety and infrastructure development and for not following international regulations, Bangladesh may lose its market share to other countries in this sector. This paper presents a financial analysis to establish compliant ship recycling facilities that will fulfill the Hong Kong Convention (HKC) requirements. This analysis has considered all the facilities of a compliant ship-recycling yard, including impermeable floors, mechanized systems, oily water separators, firefighting systems, and other special features. The worthiness, scalability, and sustainability of investing in the development of compliant ship recycling facilities have been assessed from Bangladesh’s perspective and the benefits over the conventional ones have been discussed. Also, the challenges for ship recyclers and their prevalent perspective toward establishing compliant ship recycling facilities have been depicted. Lastly, recommendations have been suggested to assist the ship recyclers in Bangladesh by encouraging them to invest and enable HKC-compliant ship recycling to harness long-term economic rewards

Ship recycling process in Bangladesh and a survey-based risk assessment with mitigation proposal

\ua9 2024 The AuthorsShip recycling industries play a significant role in the economic development of South Asian countries, including Bangladesh. In the wake of entering the Hong Kong Convention (HKC) in June 2025, the industry aims to improve its overall safety standards cost-effectively. However, due to the restrictive nature of the industry, solutions based on field surveys are limited. This study successfully articulates the indigenous industry knowledge of the recycling process in Bangladesh after carefully studying the practices followed by the existing ship recycling yards in the country. Based on field surveys conducted across 18 ship recycling yards in Bangladesh, the risk patterns inherent in the ship recycling industry are studied; for example, highly hazardous tasks in the ship recycling process are found to be (i) explosion hazards during primary cutting operations at the intertidal zone, (ii) falling hazards during inspections at the outer anchorage, (iii) falling and crushing hazards during block cutting and handling heavy objects. Industry experts and scholars consider the perception of the risk pattern regarding the current practices of ship recycling activities to cover a broader perspective of this issue. The correlation of survey outcomes with actual accident cases is comparable. Finally, practical recommendations for minimising risks have been recommended, especially in high-risk workplace areas. The study adds knowledge to the existing literature by giving a clear picture of evidence-based findings for this sector and helps improve the industry\u27s overall safety standard

f(R) theories

Over the past decade, f(R) theories have been extensively studied as one of the simplest modifications to General Relativity. In this article we review various applications of f(R) theories to cosmology and gravity - such as inflation, dark energy, local gravity constraints, cosmological perturbations, and spherically symmetric solutions in weak and strong gravitational backgrounds. We present a number of ways to distinguish those theories from General Relativity observationally and experimentally. We also discuss the extension to other modified gravity theories such as Brans-Dicke theory and Gauss-Bonnet gravity, and address models that can satisfy both cosmological and local gravity constraints.Comment: 156 pages, 14 figures, Invited review article in Living Reviews in Relativity, Published version, Comments are welcom