We numerically simulate the hydrodynamic response of a floating offshore wind turbine (FOWT) using computational fluid dynamics. The FOWT under consideration is a slack-moored 1:70 scale model of the UMaine VolturnUS-S semi-submersible platform. The test cases under consideration are (i) static equilibrium load cases, (ii) free decay tests, and (iii) two focused wave cases of different wave steepness. The FOWT is modeled using a two-phase Navier-Stokes solver inside the OpenFOAM-v2006 framework. The catenary mooring is computed by dynamically solving the equations of motion for an elastic cable using the MoodyCore solver. The results are shown to be in good agreement with measurements.
Floating breakwaters (FBs) are frequently used to protect marinas, fisheries, or other bodies of water subject to wave attacks of moderate intensity. New forms of FBs are frequently introduced and investigated in the literature as a consequence of technological advancements. In particular, a new possibility is offered by High-Density Polyethylene (HDPE) by extruding pipes of large diameters (e.g., 2.5 m in diameter) and with virtually no limit in length (hundreds of meters). By connecting two or three such pipes in a vertical layout, a novel low-cost floating breakwater with deep draft is devised. This note investigates numerically and experimentally the efficiency of this type of multi-cylindrical FBs in evaluating different geometries and aims at finding design guidelines. Due to the extraordinary length of the breakwater, the investigation is carried out in two dimensions. The 2D numerical model is based on the solution of the rigid body motion in the frequency domain, where the hydrodynamic forces are evaluated (thanks to a linear potential flow model), and the mooring forces do not include dynamic effects nor drag on the lines. The numerical predictions are compared to the results of a 1:10 scale experimental investigation. An atypical shape of the wave transmission (𝑘𝑡) curve is found, with a very low minimum in correspondence with the heave resonance frequency. The results essentially point out the influence of the position of the gravity center, the stiffness, and the mutual distance among cylinders on 𝑘𝑡.
This paper presents a detailed risk assessment framework tailored for retrofitting ship structures towards eco-friendliness. Addressing a critical gap in current research, it proposes a comprehensive strategy integrating technical, environmental, economic, and regulatory considerations. The framework, grounded in the Failure Mode, Effects, and Criticality Analysis (FMECA) approach, adeptly combines quantitative and qualitative methodologies to assess the feasibility and impact of retrofitting technologies. A case study on ferry electrification, highlighting options like fully electric and hybrid propulsion systems, illustrates the application of this framework. Fully Electric Systems pose challenges such as ensuring ample battery capacity and establishing the requisite charging infrastructure, despite offering significant emission reductions. Hybrid systems present a flexible alternative, balancing electric operation with conventional fuel to reduce emissions without compromising range. This study emphasizes a holistic risk mitigation strategy, aligning advanced technological applications with environmental and economic viability within a strict regulatory context. It advocates for specific risk control measures that refine retrofitting practices, guiding the maritime industry towards a more sustainable future within an evolving technological and regulatory landscape.
Background: Seafarers are at an increased risk of developing cardiovascular diseases (CVDs), potentially due to a stressful working environment and behavioral risk factors. To develop better prevention strategies, it is important to elucidate the extent of this risk. Therefore, we conducted a systematic literature review on CVD in seafarers. Method: We conducted systematic searches in five databases. All studies investigating CVDs among occupational seafarers, published in articles or conference papers, were eligible for inclusion. The identified records were screened and reviewed by two independent researchers, who also evaluated the methodological quality of the included studies. Results: Three thousand nine hundred and seventeen records qualified for screening, and 55 were eligible for inclusion. Most of the studies were observational, including cohort, frequency, incidence or prevalence studies, and review of case records. Around half were assessed at risk of biased findings. Participants in the studies were primarily from North America or the European continent and work onboard transportation vessels. Many studies investigated CVDs as a cause of death, focusing on conditions such as CVD, ischemic heart disease, and myocardial infarction. Frequency of CVD conditions varied but indicate that seafarers face a greater risk compared to the reference populations or control groups. Environmental factors were mainly investigated as risk factors. Conclusion: Our results indicate a higher risk of CVDs among seafarers compared to reference or control groups. However, due to the variable quality of the evidence, well-designed studies are needed to establish the causes of cardiovascular mortality and morbidity in seafarers and to investigate behavioral aspects of cardiovascular risk.
An increasing number of disruptions in ports, plants and warehouses have generated ripple effects over supply networks impacting economic activity. We demonstrate how the spread of the pandemic geographically expands the ripple effect by reducing the workers' participation in production, so undermining the ability of firms and, as a result, the entire cross-border sup- ply chain network to satisfy customers' demands. Our model of the spatio-temporal dynamics of the propagation of Covid-19 infection for supply networks contributes toward ripple effect visualisation and quantification by combining the flow of goods and materials through a typical global supply chain with an epidemiological model. The model enables prospective analyses to be performed in what-if scenarios to simulate the impact on the workforce in each node. The outcome should be helpful tools for managers and scholars. Results from this research will help mitigate the impact and spread of a pandemic in a particular region and the ability of a supply network to overcome the ripple effect. A stylised case study of a cross-border supply chain illustrates the ripple effect by showing how waves with crests at varying dates impact the ability to serve demand showing how a supply chain manager can obtain a forward-looking picture.
The widespread use of software-intensive cyber systems in critical infrastructures such as ships (CyberShips) has brought huge benefits, yet it has also opened new avenues for cyber attacks to potentially disrupt operations. Cyber risk assessment plays a vital role in identifying cyber threats and vulnerabilities that can be exploited to compromise cyber systems. Understanding the nature of cyber threats and their potential risks and impact is essential to improve the security and resilience of cyber systems, and to build systems that are secure by design and better prepared to detect and mitigate cyber attacks. A number of methodologies have been proposed to carry out these analyses. This paper evaluates and compares the application of three risk assessment methodologies: system theoretic process analysis (STPA-Sec), STRIDE and CORAS for identifying threats and vulnerabilities in a CyberShip system. We specifically selected these three methodologies because they identify threats not only at the component level, but also threats or hazards caused due to the interaction between components, resulting in sets of threats identified with each methodology and relevant differences. Moreover, STPA-Sec, which is a variant of the STPA, is widely used for safety and security analysis of cyber physical systems (CPS); CORAS offers a framework to perform cyber risk assessment in a top-down approach that aligns with STPA-Sec; and STRIDE (Spoofing, Tampering, Repudiation,Information disclosure, Denial of Service, Elevation of Privilege) considers threat at the component level as well as during the interaction that is similar to STPA-Sec. As a result of this analysis, this paper highlights the pros and cons of these methodologies, illustrates areas of special applicability, and suggests that their complementary use as threats identified through STRIDE can be used as an input to CORAS and STPA-Sec to make these methods more structured.
This paper investigates the influence of a crown wall on wave overtopping on rubble mound breakwaters. Existing data is used to modify the EurOtop overtopping formula updated by Eldrup et al. (2022) to cover the influence of the crown wall. The effect of raising the wall above the armor crest (elevated wall) or lowering the wall below the armor crest (lowered wall) is investigated. A crown wall at the armor crest level is considered as the reference case. By increasing the elevation of either the armor crest or the crown wall, overtopping is reduced and by lowering either of them, overtopping increases. The influence of the crown wall height, elevated or lowered compared to the armor crest, is not considered accurately in the present design guidelines and thus corrections are suggested. For an elevated wall, a modified crest width has been defined, to better describe the presence of the armor crest in front of the wall. For the lowered wall the effective freeboard might be taken as the average of the wall and armor freeboards. The improvement compared to existing methods is significant, especially for breakwaters with a large elevated wall. The proposed modifications to the EurOtop Manual increase the range of applicability with respect to the wall configuration.
The management of produced water (PW) discharges from offshore oil and gas installations in the North Atlantic is under the auspices of OSPAR (Oslo/Paris convention for Protection of the Marine Environment of the North-East Atlantic). In 2010, OSPAR introduced the Risk Based Approach (RBA) for PW management. The RBA includes a hazard assessment estimating PW ecotoxicity using two approaches: Whole Effluent Testing (WET) and Substance Based (SB). Set against the framework of the WET and SB approach, this study conducted a literature review on the magnitude and cause of PW ecotoxicity, respectively, and on the challenges of estimating these. A large variability in the reported magnitude of PW WET was found, with (E/L)C50-values ranging from 100% and a median of 11% (n=301). Metals, hydrocarbons, and production chemicals were identified as causing ecotoxicity across literature. However, this review reveals how knowledge gaps on PW composition and high sample- and species-dependency of PW ecotoxicity makes clear identification and generalization difficult. It also highlights how limitations regarding availability and reliability of ecotoxicity data result in large uncertainties in the subsequent risk estimates, which is not adequately reflected in the RBA output (e.g. environmental impact factors). Thus, it is recommended to increase the focus on improving ecotoxicity data quality before further use in the RBA, and that WET should play a more pronounced role in the testing strategy. To increase the reliability of the SB approach, more attention should be given to the actual composition of PW. Bioassay-directed chemical analysis, combining outcomes of WET and SB in toxicity identification evaluations, may hold the key to identifying drivers of ecotoxicity in PW. Finally, an uncertainty appraisal must be an integrated part of all reporting of risk estimates in the RBA, to avoid mitigation actions based on uncertainties rather than reliable ecotoxicity estimations.
We contribute to theorizing global human resource strategy by analyzing the mobility of workers laid off due to the failure of a MNC employer. The job opportunities of laid-off workers are affected by their industry legitimacy. Focusing on scarce specialized workers, we propose that prospective MNC employers share an interest in retaining such workers' legitimacy. However, in the light of organizational failure, they may suffer from cross-border legitimacy loss conditioned by their former employer's MNC structure—specifically, their former organizational units or geographical locations. We present an illustrative case study of traders laid off by a spectacular bankruptcy in the global bunker industry. This inspires a discussion of how MNC top management can manipulate worker legitimacy following an organizational failure. Managerial Summary: Strategic hiring of globally mobile scarce specialized workers is central to global human resource strategy. We analyze what drives the legitimacy and mobility of such workers after being laid off by a bankruptcy of their former employer. We demonstrate that laid off workers experience comparatively high legitimacy loss when they were previously assigned to an MNC organizational unit or geographical location where other workers were suspected of being responsible for failure. This weakens their bargaining position vis-a-vis a prospective employer. We present an illustrative case study of traders laid off by a spectacular bankruptcy in the global bunker oil industry.
This paper explores the ways in which maritime labor, maritime risk, and seafarers’ survival are embedded in the financial logics and practices of the global shipping industry. By employing the notion of “existential arbitrage,” the ethnography moves through the pursuit of global profit to the value of labor as a commodity, human and financial risk, and ultimately the value of human lives, all of which are arbitraged. Arbitrage is a profit strategy that is based on a belief in the equalizing power of the market yet is predicated on and creates difference among commodities in order to create opportunities to generate profit. Existential arbitrage brings anthropological studies of security and conflict and trade and finance together. By taking the interdependence of these subfields seriously and showing how the relationship between them manifests itself in practice, the notion of existential arbitrage uncovers a brutal financial trading strategy that requires and forces the oscillation between notions of valuable life and the valuation of labor commodities in a competitive global market.