This study delves into computational fluid dynamics (CFD) applied to roll decay tests for Floating Production, Storage, and Offloading units. The main objective of this work is to investigate complexities of the corresponding CFD simulations and aspects of the numerical setup optimization to enhance understanding of factors influencing precision, computational efficiency, and reliability in such numerical applications. Moreover, different bilge keel configurations along with the presence of other submerged appendages are studied and assessed in a compendious manner.
The coupling loss factor (CLF) is an essential parameter in the rapid assessment of high-frequency structural vibration and sound. This paper utilizes the wave motion theorem to formulate the CLF between two flat plates connected at any angle under harmonic wave incidence. The derived CLF formulation is rigorously validated through literature comparison and commercial software simulations. Numerical results reveal that the CLF exhibits pronounced dependence on the incident wave characteristics while demonstrating significant correlations with excitation frequency, coupling configuration, material properties, and geometric parameters of the structural system. This research significantly enhances comprehension of structural energy attenuation.
To evaluate the performance of real-time energy management strategies, we utilize the dynamic programming method to find the optimal energy flow allocation among two engines and batteries for a dual-engine hybrid power system (DHPS). First, the mathematical models of the DHPS are established. Then, the optimization problem, aimed at minimizing fuel consumption, is formulated. Next, the flowchart of the energy management strategy based on dynamic programming is introduced. Finally, the superiority of the proposed method is validated by comparing it with two real-time energy management strategies. The results show that up to 12.79% of fuel consumption is saved.
To achieve carbon neutrality by 2050, 50,000 m3 liquefied hydrogen storage tanks are being developed. A key design challenge is fatigue from repeated refilling and seismic events. The fatigue crack propagation behavior at cryogenic temperatures, especially with the martensitic transformation of austenitic stainless steels, is unclear. In this study, low-cycle fatigue tests were performed at different temperatures and materials to investigate the relationship between crack tip opening displacement (CTOD) and crack growth rate. The effect of martensitic transformation on CTOD was quantified by electron backscatter diffraction. These results were used to estimate crack propagation in large tanks.
This paper is to study the influence of soil liquefaction on the seismic response of a monopile foundation for the Technical University of Denmark (DTU) 10-MW reference wind turbine (RWT) on the west coast of Taiwan. Taiwan is located in seismically active regions, and the soil conditions of Taiwan's offshore wind farms are softer than those in Europe. Therefore, there is significant interest in assessing the behavior of a wind turbine subjected to seismic load. Based on the flexible volume method and the practical, two-surface plastic constitutive model for sand (P2PSand), the two foundation models of the DTU 10-MW RWT are employed to carry out a series of seismic design load cases as defined in DNV-RP-0585. The results show that soil liquefaction has significant influence on the dynamic response of the DTU 10-MW RWT with monopile foundation under the local environmental conditions in Taiwan. In particular, vertical displacements and rotations are significantly amplified by soil liquefaction during strong ground motions. It means that without considering the potential effect of soil liquefaction, structural responses, including displacement and rotation angle, may be greatly underestimated.
The open ocean water mass has affected the water quality of the Seto Inland Sea. In this study, the entering path and behavior of the open ocean water mass were analyzed using a three-dimensional flow simulation and Lagrangian particle tracking. The analyses revealed that the entering paths changed significantly, depending on the path of the Kuroshio Current. The entering of open ocean water may affect the water quality and primary production not only in the Kii Channel adjacent to the Pacific Ocean but also in other sea areas, including Harima Nada and Osaka Bay.
To tackle the challenges confronted by traditional deep-draft SEMI, a novel donut-type platform featuring a large moon pool is put forward. The computational fluid dynamics method integrated with wind tunnel and wave basin experiments has been employed for moon pool response analysis and for time-domain coupling analysis of the mooring system and steel catenary risers (SCRs). The results show that the donut-type platform has good global performance benefiting from the moon pool damping effect, and the feasibility for SCR application is demonstrated. With additional advantages such as lower topside elevation, larger storage capacity, higher hull structural strength, and better constructability, the donut-type platform could be a competitive new conceptual hull option for SCR utilization.
Due to their corrosion resistance, bolting assemblies manufactured from stainless steel are becoming more and more important in various applications, such as in offshore structures and machinery. An enhanced level of knowledge based on publications of the last few years offers opportunities of using preloaded bolting assemblies. However, missing design rules and insufficient data on the fatigue strength of stainless steel bolting assemblies limit their application. Neither Eurocode 3 for structural engineering nor VDI 2230-1 for mechanical engineering provide sufficient design rules regarding the verification of the fatigue strength of stainless-steel bolts. A total of 345 fatigue tests at constant amplitude loading up to 107 load cycles were carried out on bolting assemblies made from austenitic, duplex stainless steel and carbon steel in nominal sizes, M6, M12, and M20, with strength grades, 80 and 100 (8.8/10.9).
In this paper, the authors describe their validation and verification exercises with the novel Scale Resolving Hybrid (SRH) turbulence model, also known as the Hybrid Temporal Large Eddy Simulation, in application to the CFD analysis of aerodynamic performance of wind turbines. Focusing on the two benchmark cases - UAE reference wind turbine and DTU 10 MW wind turbine - investigations include the prediction of rotor thrust and torque, blade bending moment, pressure distributions at different sections along the blade span, as well as vorticity field in the rotor wake. The SRH model is shown to provide a good balance between the accurate prediction of integral loads on the turbine and high-fidelity resolution of field variables. Accurate prediction of blade pressure distribution under varying operating conditions is an essential result for the analysis of unsteady blade deformations and the resulting fatigue loads. Detailed resolution of vortex structures in rotor wake as observed in the experiment remains a challenge due to the need for very fine spatial and temporal resolutions. The latter aspects will be addressed in future studies, particularly regarding full scale operating conditions.
Hydrogen embrittlement for SUS316L weld metal is investigated in this work by analyzing the failure mechanism of slow strain rate tensile specimens tested in a high-pressure hydrogen environment. Tungsten inert gas (TIG) weld metal (WM) specimens, which showed delta ferrite and austenite in the microstructure, were pre-strained in the helium environment at 4 K to induce a-martensite before testing in hydrogen. Shielded metal arc welding (SMAW) and submerged arc welding (SAW) WM specimens were tested in the condition of the most severe case, without pre-strain, to clarify the participation of martensite and delta ferrite in the loss of ductility and in the failure process induced by hydrogen. The degradation and failure modes were assessed using a scanning electron microscope, electron back scattered diffraction, and energy-dispersive x-ray spectroscopy. The loss of ductility by the hydrogen embrittlement (HE) at low temperatures was more significant on the TIG WM specimens, and this was mainly promoted by a higher content of delta ferrite and martensite, which served as paths for the hydrogen to induce crack propagation in a quasi-cleavage pattern. Delta ferrite and martensite competed to cause higher degradation in the TIG WM, with delta ferrite being the predominant crack path, and a-martensite as a booster of the HE. SMAW WM showed a better HE resistance, which can be related to the lower Md30 temperature and the negligible presence of delta ferrite.
This study presents methodologies to simulate material hardening and rate-dependent behaviors in umbilical and subsea power cable elements using an earlier developed multi-linear hysteresis model. The model employs interpolation and boundary correction techniques to adapt the stress-strain response based on established principles of rate dependency and plasticity. Validation of the methodology demonstrates its ability to replicate expected material responses in the time domain. The findings highlight the model's versatility and its potential application in simulations to assess the structural integrity of subsea cable elements under complex loading conditions.
In this study, thermal-fluid-solid coupled simulations on the gas-phase pre-cooling operation of the corrugated cryogenic hoses were performed. Attention was focused on the temporal evolution and spatial distribution of transient thermal stress in the hose structure caused by convective heat transfer of the cooling medium, Liquefied Natural Gas Boil-Off Gas (BOG). The effects of different corrugated hose parameters, i.e., boundary conditions, hose lengths, BOG inlet flow rates, and corrugation shapes (C-type and U-type), on the transient thermal stress behavior were thoroughly assessed. The thermal stress developed at different locations of the corrugated hoses with these parameters is found to be governed by two major factors: the boundary constraint and local temperature gradient. The objective of this study is to offer practical insights for the structural strength design of corrugated cryogenic hoses and effective pre-cooling strategies, aiming to mitigate structural safety risks caused by excessive thermal stress.
Cumberland Plain Woodland (CPW) is the original native vegetation of the shale soils in Western Sydney but now so reduced in extent that it has been declared a Critically Endangered Ecological Community. While the species composition of above-ground CPW is well documented, this is not the case for the below-ground seedbank. An investigation of the below-ground seedbank was undertaken for two sites of remnant CPW to determine species presence, growth form and numbers, and whether germination treatments of smoke, heat or fire affected species composition. Soil blocks taken in June 2001 were subjected to the following treatments: untreated controls, aerosol smoke, heat, smoke and heat, or fire. Seedlings were counted over July-November and left to grow on to allow identification where possible. A total of 10,436 seedlings appeared, of which 7,596 from 60 taxa were identified. The study showed that natives were present in the seedbank, were responsive to germination cues and outnumbered exotics both in species richness and number of seedlings. Of the identified seedlings, 43 were native species and 17 were exotics. Native forbs, shrubs and grasses each had 10 or more species. Exotics were largely forbs and some grasses. 39% of the CPW groundcover and shrub indicator species appeared in the experiment. Germination treatments significantly increased total natives species richness; smoke alone gave a significant increase over the control, and heat or heat plus smoke gave further significant increases. Species richness of exotics did not respond to any of the germination treatments. Seedlings numbers were dominated by natives, with 6,503 counted (5,011 identified as Themeda triandra). Exotics numbered 1,073 seedlings. Germination treatments significantly increased numbers of seedlings for native shrubs, and approached significance for total natives and for grasses. Numbers of exotic seedlings, while highest in the controls, did not vary significantly with germination treatments. Seedlings from 8 individual species responded to germination treatments in the same way over both sites; 4 were natives in which numbers of seedlings increased, and in a further 4 species (1 native, 3 exotic) numbers of seedlings decreased. Species composition was significantly affected by heat and by site; but smoke effect only approached significance. Heat and smoke effects were consistent across the two sites. Plotting the nMDS analysis grouped the controls with the smoke treatment, which were separate from the treatments with a heat component. Analysis of species contributing to cumulative similarity showed thatthe number of native species was lowest in the controls, but this progressively increased over the smoke, heat, smoke and heat and fire treatments.
The Linnean Society of New South Wales was `instituted for the Cultivation and Study of the Science of Natural History, in all its Branches' and was founded in Sydney, New South Wales (Australia) in 1874. Since that time the journal of the Society, Proceedings of the Linnean Society of New South Wales, has published many valued contributions to the study of natural history in all its forms in Australasia. In 2025 we celebrate 150 years of publication, trusting that the Proceedings will remain a hallmark of the Society's activities.
Pherosphaera fitzgeraldii Dwarf Mountain Pine, a rare conifer (Podocarpaceae) restricted to the Upper Blue Mountains in eastern Australia, is described in some sources as dioecious, like its closest relative Tasmanian Pherosphaera hookeriana. This review of early collections shows that dioecy was assumed from the first collection, but that monoecy was also recognised at that time. An assessment of 37 herbarium sheets with specimens from Sydney, Melbourne and Kew (UK) herbaria using recently available high-resolution photographs shows that monoecy is common in the species and has been under-reported. This review confirms current field observations of monoecy and provides new information about the reproductive system for those working on conservation of this critically endangered species.
The rugose coral species Entelophyllum latum is described from the Yarralumla Formation of Canberra. As the species was first recognised in the Glenbower Formation a little to the north of Canberra, and does not occur anywhere else in the Canberra-Yass region, it confirms correlation of the two formations, which on recently revised conodont data are now very likely to be of Sheinwoodian (mid-Wenlock) age.
Community involvement in science, driven largely by advances in digital photography and the widespread use of online databases, has experienced exponential growth over the past decade. This study focuses on potential opportunities in iNaturalist, the leading international platform for community science observations, covering all life-forms. It is essentially based on photographs, usually in the field. iNaturalist is now the largest global contributor of insect species records from community science observations; the surge in observational data offers the potential to address significant gaps in the scientific record. We analysed entomological data from the platform to evaluate the volume, growth trends, and quality of submissions. We also surveyed iNaturalist's top insect identifiers to identify opportunities for enhancing data utility and community engagement. The survey responses explored the various reasons for many observations being unavailable to be identified to Research Grade status. Based on our findings, we propose a development framework to enhance the research utility of community science data in entomology and to better leverage its potential. This includes the establishment of an entomology "Community of Practice", an advisory group comprising a diverse group of influential leaders within the stakeholder communities, to guide future initiatives. The objective would be to formulate actionable strategies for improving the use of iNaturalist and resolve the issues raised by the wider Naturalist stakeholder community. While this paper focuses on iNaturalist, the findings may have applicability for other platforms.
The Rookery Limestone Member is exposed in a small area on 'The Rookery', southeast of Cobar in central NSW. An Early Devonian, either Lochkovian or Pragian, age for the stratum was previously determined based on the brachiopod, trilobite and conodont faunas preserved. Microvertebrate remains include scales of acanthodians Nostovicina guangxiensis and Trundlelepis cervicostulata; scales and dermal bone fragments possibly of the placoderm Connemarraspis; and scales, dermal bone fragments, and possible gnathal plates of a romundinid placoderm. Alternatively, the gnathal plates could be from the stem osteichthyan Lophosteus incrementus. This fauna indicates a late Lochkovian age based on the stratigraphic distribution of these taxa elsewhere in NSW, and accords with dating suggested by the conodont taxa from the same samples.
Modern field development entails the construction of subsea pipe-in-pipe systems in an optimized, cost-effective solution. Clients aim to mitigate risks at an early stage and seek rapid design convergence while reducing development costs. Linking in-place pipeline behaviour with installation techniques is a common source of cost efficiency and overall system design improvement. This paper presents a study aimed at finding an optimum balance between lateral buckling mitigation and the distribution of the internal load sharing devices (i.e. bulkheads) installed along the pipeline.
Vortex-Induced Vibrations (VIV) from fatigue damage due to current loads has become a challenge for ultra-deepwater projects, and the installation of strakes along the riser is typically used for VIV suppression. The present study indicates that by maintaining the same total coverage length while simply optimizing the arrangement of strakes, a significant reduction in VIV damage may be achieved. The optimized strake configuration, with a significant improvement in fatigue response, promotes a reduction of strake procurement and installation compared to a fully straked riser. The reduction on material procurement, fabrication, handling, and installation represents a significant cost saving in the project scope.
