bluuebunny/crossref_metadata_2025 huggingface dataset:
Microbiota‐derived butyrate dampens linaclotide stimulation of the guanylate cyclase C pathway in patient‐derived colonoids
Authors: Velez Lopez Alejandro , Waddell Amanda , Antonacci Simona , Castillo Daniel , Santucci Neha , Ollberding Nicholas J. , Eshleman Emily M. , Denson Lee A. , Alenghat Theresa
Published: September 2023

Background & Aims

Disorders of gut‐brain interaction (DGBI) are complex conditions that result in decreased quality of life and a significant cost burden. Linaclotide, a guanylin cyclase C (GCC) receptor agonist, is approved as a DGBI treatment. However, its efficacy has been limited and variable across DGBI patients. Microbiota and metabolomic alterations are noted in DGBI patients, provoking the hypothesis that the microbiota may impact the GCC response to current therapeutics.

Methods

Human‐derived intestinal organoids were grown from pediatric DGBI, non‐IBD colon biopsies (colonoids). Colonoids were treated with 250 nM linaclotide and assayed for cGMP to develop a model of GCC activity. Butyrate was administered to human colonoids overnight at a concentration of 1 mM. Colonoid lysates were analyzed for cGMP levels by ELISA. For the swelling assay, colonoids were photographed pre‐ and post‐treatment and volume was measured using ImageJ. Principal coordinate analyses (PCoA) were performed on the Bray–Curtis dissimilarity and Jaccard distance to assess differences in the community composition of short‐chain fatty acid (SCFA) producing microbial species in the intestinal microbiota from pediatric patients with IBS and healthy control samples.

Key Results

Linaclotide treatment induced a significant increase in [cGMP] and swelling of patient‐derived colonoids, demonstrating a human in vitro model of linaclotide‐induced GCC activation. Shotgun sequencing analysis of pediatric IBS patients and healthy controls showed differences in the composition of commensal SCFA‐producing bacteria. Butyrate exposure significantly dampened linaclotide‐induced cGMP levels and swelling in patient‐derived colonoids.

Conclusions & Inferences

Patient‐derived colonoids demonstrate that microbiota‐derived butyrate can dampen human colonic responses to linaclotide. This study supports incorporation of microbiota and metabolomic assessment to improve precision medicine for DGBI patients.
Diel and seasonal stem growth responses to climatic variation are consistent across species in a subtropical tree community
Authors: Zhou Bo , Sterck Frank , Kruijt Bart , Fan Ze‐Xin , Zuidema Pieter A.
Published: September 2023

Understanding how intra‐annual stem growth responds to atmospheric and soil conditions is essential for assessing the effects of climate extremes on forest productivity. In species‐poor forests, such understanding can be obtained by studying stem growth of the dominant species. Yet, in species‐rich (sub‐)tropical forests, it is unclear whether these responses are consistent among species.

We monitored intra‐annual stem growth with high‐resolution dendrometers for 27 trees belonging to 14 species over 5 yr in a montane subtropical forest. We quantified diel and seasonal stem growth patterns, verified to what extent observed growth patterns coincide across species and analysed their main climatic drivers.

We found very consistent intra‐annual growth patterns across species. Species varied in the rate but little in the timing of growth. Diel growth patterns revealed that – across species – trees mainly grew before dawn when vapour pressure deficit (VPD) was low. Within the year, trees mainly grew between May and August driven by temperature and VPD, but not by soil moisture.

Our study reveals highly consistent stem growth patterns and climatic drivers at community level. Further studies are needed to verify whether these results hold across climates and forests, and whether they can be scaled up to estimate forest productivity.
A new set of international Leptosphaeria maculans isolates as a resource for elucidation of the basis and evolution of blackleg disease on Brassica napus
Authors: Van de Wouw Angela P. , Scanlan Jack L. , Al‐Mamun Hawlader A. , Balesdent Marie‐Hélène , Bousset Lydia , Burketová Lenka , del Rio Mendoza Luis , Fernando W. G. Dilantha , Franke Coreen , Howlett Barbara J. , Huang Yong‐Ju , Jones E. Eirian , Koopmann Birger , Lob Suhaizan , Mirabadi Ali Z. , Nugent Bridgit C. , Peng Gary , Rossi Franco R. , Schreuder Huibrecht , Tabone Annie R. , Van Coller Gert J. , Batley Jacqueline , Idnurm Alexander
Published: September 2023

A collection of isolates of the fungi Leptosphaeria maculans and L. biglobosa, which cause blackleg disease on Brassica napus (canola/oilseed rape) and other Brassicaceae species, was assembled to represent the global diversity of these pathogens and a resource for international research. The collection consists of 226 isolates (205 L. maculans and 21 L. biglobosa) from 11 countries. The genomes of all 205 L. maculans isolates were sequenced, and the distribution and identity of avirulence gene alleles were determined based on genotypic information and phenotypic reactions on B. napus lines that hosted specific resistance genes. Whilst the frequencies of some avirulence alleles were consistent across each of the regions, others differed dramatically, potentially reflecting the canola/oilseed rape cultivars grown in those countries. Analyses of the single‐nucleotide polymorphism (SNP) diversity within these L. maculans isolates revealed geographical separation of the populations. This "open access" resource provides a standardized set of isolates that can be used to define the basis for how these fungal pathogens cause disease, and as a tool for discovery of new resistance traits in Brassica species.
Ghrelin is related to lower brain reward activation during touch
Authors: Pfabigan D. M. , Frogner E. R. , Schéle E. , Thorsby P. M. , Skålhegg B. S. , Dickson S. L. , Sailer U.
Published: September 2023

The gut hormone ghrelin drives food motivation and increases food intake, but it is also involved in the anticipation of and response to rewards other than food. This pre‐registered study investigated how naturally varying ghrelin concentrations affect the processing of touch as a social reward in humans. Sixty‐seven volunteers received slow caressing touch (so‐called CT‐targeted touch) as a social reward and control touch on their shins during 3T functional imaging on two test days. On one occasion, participants were fasted, and on another, they received a meal. On each occasion, plasma ghrelin was measured at three time points. All touch was rated as more pleasant after the meal, but there was no association between ghrelin concentrations and pleasantness. CT‐targeted touch was rated as the most pleasant and activated somatosensory and reward networks (whole brain). A region‐of‐interest in the right medial orbitofrontal cortex (mOFC) showed lower activation during all touches, the higher the ghrelin concentrations were. During CT‐targeted touch, a larger satiety response (ghrelin decrease after the meal) was associated with higher mOFC activation, and this mOFC activation was associated with higher experienced pleasantness. Overall, higher ghrelin concentrations appear to be related to a lower reward value for touch. Ghrelin may reduce the value of social stimuli, such as touch, to promote food search and intake in a state of low energy. This suggests that the role of ghrelin goes beyond assigning value to food reward.
Health inequities in dialysis care: A scoping review
Authors: Purcell Lindsey Kay , Schnitker Joseph William , Moore Ty Michael , Peña Andriana Mercedes , Love Mitchell Faris , Ford Alicia Ito , Vassar Benjamin Matt
Published: September 2023

Main Problem

We aim to look at potential gaps in current dialysis literature on inequities and explore future research that could contribute to more equitable care.

Methods

Following guidelines from the Joanna Briggs Institute (JBI) and the Preferred Reporting Items for Systematic reviews and Meta Analyses extension for Scoping Reviews (PRISMA‐ScR), we conducted a scoping review of health inequities in dialysis. PubMed and Ovid Embase were searched in July 2022 for articles published between 2016 and 2022 that examined at least one of the following NIH defined health inequities: race/ethnicity, sex/gender, LGBTQ+ identity, underserved rural populations, education level, income, and occupation status. Frequencies of each health inequity as well as trends over time of the four most examined inequities were analyzed.

Results

In our sample of 69 included studies, gaps were identified in LGBTQ+ identity and patient education. Inequities pertaining to race/ethnicity, sex/gender, underserved rural populations, and income were sufficiently reported. No trends between inequities investigated over time were identified.

Conclusions

Our scoping review examined current literature on health inequities pertaining to dialysis and found gaps concerning LGBTQ+ and patients with lower levels of education. To help fill these gaps, and possibly alleviate additional burden to these patients, we recommend cultural competency training for providers and dialysis center staff as well as community‐based educational programs to improve dialysis patients' health literacy.
Missed nursing care in relation to registered nurses' level of education and self‐reported evidence‐based practice
Authors: Falk Ann‐Charlotte , Boström Anne‐Marie , Nymark Carolin , von Vogelsang Ann‐Christin
Published: September 2023

Background

Patient safety is one of the cornerstones of high‐quality healthcare systems. Evidence‐based practice is one way to improve patient safety from the nursing perspective. Another aspect of care that directly influences patient safety is missed nursing care. However, research on possible associations between evidence‐based practice and missed nursing care is lacking.

Aim

The aim of this study was to examine associations between registered nurses' educational level, the capability beliefs and use of evidence‐based practice, and missed nursing care.

Methods

This study had a cross‐sectional design. A total of 228 registered nurses from adult inpatient wards at a university hospital participated. Data were collected with the MISSCARE Survey‐Swedish version of Evidence‐Based Practice Capabilities Beliefs Scale.

Results

Most missed nursing care was reported within the subscales Basic Care and Planning. Nurses holding a higher educational level and being low evidence‐based practice users reported significantly more missed nursing care. They also scored significantly higher on the Evidence‐based Practice Capabilities Beliefs Scale. The analyses showed a limited explanation of the variance of missed nursing care and revealed that being a high user of evidence‐based practice indicated less reported missed nursing care, while a higher educational level meant more reported missed nursing care.

Linking evidence to action

Most missed nursing care was reported within the subscales Planning and Basic Care. Thus, nursing activities are deprioritized in comparison to medical activities. Nurses holding a higher education reported more missed nursing care, indicating that higher education entails deeper knowledge of the consequences when rationing nursing care. They also reported varied use of evidence‐based practice, showing that higher education is not the only factor that matters. To decrease missed nursing care in clinical practice, and thereby increase the quality of care, educational level, use of evidence‐based practice, and organizational factors must be considered.
Performance of Finned Absorber Plate Solar Air Heater Having Multiple Triangular Air Flow Passages in Parallel Under Transition to Turbulent Flow Condition
Authors: Karwa Rajendra
Published: September 2023

This paper presents the results of thermal performance study of a solar air heater having absorber plate with inclined fins fitted in equilateral triangular flow passages in parallel using the governing equations under transition to turbulent flow and compares the same with the conventional solar air heater having low aspect ratio rectangular air flow duct at equal pumping power condition. The equal pumping power condition for the equilateral triangular passages of width w and rectangular duct height H has been found to be w = 2.65 H. The finned absorber plate solar air heater has been found to provide 7.3–25.8% better thermal efficiency than the conventional air heater because of the substantial increase in the effective heat transfer surface area due to the fins. The effects of variation of design, ambient, and operating parameters on the performance of the finned solar air heater show that the triangular passage width w must be increased with the increase in the collector length L to satisfy the condition of equal pumping power according to the relation w3/L2.75 = constant. The results of the present study can be utilized for the development of enhanced-performance finned solar air heater with triangular passages.
Hydrodynamic Response Analysis of Ultra-Deep Water FPSO System Using Ansys Aqwa, Wamit, and HydRA
Authors: Sridhar K. , Sannasiraj S. A. , Sundaravadivelu R.
Published: September 2023

Offshore energy resources are essential to the growth of a future civilization. For offshore production, deep and ultradeep water fields are an ideal option. FPSOs are the most commonly installed platform compared to the other types. In this paper, the numerical hydrodynamic response analysis of an FPSO system has been performed using ANSYS Aqwa, Wamit, and HydRA. ANSYS Aqwa is a commercial software used widely in the offshore industry for offshore structure hydrodynamic analyses. WAMIT is the most efficient tool for examining wave interactions with offshore platforms and other structures or vessels. HydRA (Hydrodynamic Response Analysis) is a code developed at IIT Madras that simulates marine and offshore structure linear and nonlinear dynamics. The motion response study of the FPSO platform has been conducted without mooring lines at 2100m water depth and for two different load cases of ballast loaded and fully loaded condition, with the wave headings of 90°. The experimental results of a model study conducted for the FPSO model in the wave basin, IIT Madras have been compared and validated with numerical results of the fully loaded case. Finally, the compatibility of the numerical tools used for the hydrodynamic analysis has been discussed.
Interceptor Effect on Lift and Drag in High Speed Planing Hull
Authors: J. Suneela , Korra Naveen
Published: September 2023

In this paper an attempt has been made to study the effectiveness of interceptor on lift and drag as this device is nowadays used by both partial and dynamic lift crafts. There is change in pressure distribution at the stern region where interceptor is fitted which helps in the lift of vessel. This study focuses on the effect of interceptor in high speed planing hull with 20deg deadrise angle based on experimental, numerical and empirical approaches. Experiments were conducted in the Towing Tank facility, Department of Ocean Engineering at IIT Madras and numerical simulations were carried out in still water condition for the cases of the hull with and without interceptor. Results showed good reduction in resistance and trim of the vessel when fitted with interceptor in planing regime. Savitsky empirical relations for bare hull and Steen empirical equations for hull with interceptor are used to estimate lift and drag on the vessel. The results of this study show that interceptor creates more lift on the vessel due to the pressure created at the stern region which helps in drag reduction and further in better control of trim on the vessel. Measurements were also made to confirm that interceptor has an effect on the dynamic lift of the hull and hence a change in resistance resulting in control of the trim angle.
Modelling and Operation of a Hybrid LNG Propulsion Tugboat
Authors: Mohamed Roslan Sharul Baggio , Konovessis Dimitrios , Ang Joo Hock , Menon Nirmal Vineeth , Tay Zhi Yung
Published: September 2023

The need to reduce ship emissions and the increase in fuel oil prices has driven the interest in incorporating alternative energy solutions to traditional power systems in the maritime industry. In this paper, a hybrid energy system of liquified natural gas (LNG) and batteries for a tugboat is developed and studied. The flexibility of the load allocation is believed to reduce fuel consumption and emission as the tugboats with dynamic power profiles benefited from splitting the load among the multiple power sources. The hybrid system model is created in MATLAB/Simulink®. In addition, fuel data recorded from an operational diesel propulsion tugboat is used where the generated operational data are replicated in the Simulink model before any further analysis and comparisons are conducted. The LNG-hybrid system is tested in three different configurations without the battery in both fixed speed and variable speed, and with a battery. The daily fuel cost, CO2 emissions, energy efficiency operation indicator (EEOI) and CII ratings are then calculated for the different configurations in three different operation cases for comparison studies. The results demonstrate that an average reduction of CO2 by 64.7% and a lowering average of daily fuel cost by 67.5% for an LNG battery hybrid tugboat are achieved as compared to a diesel system.
Inspection Planning in the Marine Sector, A Case Study of a Hydrogen-Fueled Fishing Vessel
Authors: Giannini Leonardo , Jafarzadeh Sepideh , Campari Alessandro , Ustolin Federico , Paltrinieri Nicola
Published: September 2023

Inspection planning, maintainability and safety aspects are yet to be consolidated topics of hydrogen technologies in most of their applications, including the marine sector. The implementation of electricity in the marine sector is almost only appealing for ferries, which in many cases have daily access to recharge stations. In addition, the climate roadmap of the Norwegian fishing fleet estimates that a low environmental impact technology can contribute to significantly reduce greenhouse emissions, especially carbon dioxide, by 2030. In fact, considering the longer working sessions of fishing vessels, the additional weight of batteries, and the considerable occupied volume, it is more than reasonable to discuss fuel cells as a possible solution. Against this background, this paper discusses a case study of a hydrogen-fueled fishing vessel, focusing on risk-based inspection (RBI) and maintenance planning as a way to significantly decrease safety-related uncertainties and optimize the associated operations. Different hydrogen-induced degradation mechanisms have been considered to investigate how the existing RBI standards might lead to an underestimation of the risks associated with the equipment selected for the fishing vessel. In addition, a discussion regarding the limitations in the applicability of standard RBI planning with respect to hydrogen technologies is carried out as an overall result, along with the limits of the implemented approach.
A Study on the Degree of Bending (DOB) in Two-Planar Tubular DYT-Joints of Offshore Jacket Structures: Geometrical Effects and Fatigue Design Formulation
Authors: Ahmadi Hamid , Karampour Hassan , Ghorbani Mahdi , Fard Hamid
Published: September 2023

Through-the-thickness stress distribution in a tubular member has a profound effect on the fatigue behavior of tubular joints commonly found in steel offshore structures. This stress distribution can be characterized by the degree of bending (DoB). Although multi-planar joints are an intrinsic feature of offshore tubular structures and the multi-planarity usually has a considerable effect on the DoB values at the brace-to-chord intersection, few investigations have been reported on the DoB in multi-planar joints due to the complexity of the problem and high cost involved. In the present research, data extracted from the stress analysis of 243 finite element (FE) models, verified based on available parametric equations, was used to study the effects of geometrical parameters on the DoB values in two-planar tubular DYT-joints. Results showed that it is quite common for an axially loaded two-planar DYT-joint to have a low DoB. Therefore, when the current standard HSS-based S-N approach is used for the fatigue analysis of axially loaded two-planar DYT-joints, results should be modified to include the effect of the DoB in order to obtain more accurate fatigue life prediction. It was also concluded that for axially loaded two-planar DYT-joints, the parametric formulas of uniplanar YT-joints are not applicable for the DoB prediction, since such formulas may lead to under-/over-predicting results. Parametric FE study was followed by a set of nonlinear regression analyses to develop six new DoB parametric equations for the fatigue analysis and design of axially loaded two-planar DYT-joints.
A Wave Run-Up Empirical Modelling Comparison Study for a Scale Model Semi-Submersible Floating WTG Platform
Authors: Foster Tegan S. , Ghadirian Amin , Borg Michael , Hyldahl Per C. , Venugopal Vengatesan , Tao Longbin , Johanning Lars
Published: September 2023

As part of the ongoing development of the Stiesdal Offshore A/S TetraSub floating offshore wind turbine generator (WTG) platform, this study investigates wave run-up acting on the front cylindrical ballast tanks. Using experimental results from a recent test campaign of a TetraSub variant 1:50 scale model, this work aims to review existing semi-empirical methods for predicting wave run-up.

Moreover, for the defined eight regular wave test cases, predicted theoretical values are compared to the measured values recorded during tank experiments. The outcomes from this investigation will contribute to modelling methods used within future front-end engineering design (FEED) and detailed design stages of floating platforms, in order to develop robust and cost-effective solutions.
Combined Fatigue Damages of Bridges From Wind and Wave Actions: Application to Offshore Bridge Structures
Authors: Knoph Magnus , Sigurdsson Gudfinnur , Devergez Mélanie
Published: September 2023

Traditionally, fatigue analyses of offshore bridge structures are calculated separately for the wind and the wave load processes. The total accumulated fatigue damage is often calculated by combining the calculated accumulated fatigue damages from these two processes by using analytic expressions. One widely used approach to combine fatigue damage from wind and wave load is the method from DNV-RP-C203 [1]. It is demonstrated that the use of this method may lead to conservative estimations of the fatigue damage for certain hot spots. Applying conservative values for the accumulated fatigue damage may lead to more frequent in-service inspections, as the calculated fatigue damage is the main input to inspection planning. To obtain a more appropriate inspection plan that is optimised regarding both integrity and cost, a new method combining wave and wind fatigue damages for offshore bridges is proposed. The selected case study is based on typical North Sea MetOcean conditions but is generally also applicable for other offshore locations. The new method results in significantly longer calculated fatigue lives for certain hot spots than obtained by using the method from DNV-RP-C203. By applying more accurate and consistent fatigue calculation approach will also lead to more sound and consistent in-service inspection plans for fatigue cracks which may reduce number of unnecessary in-service inspections.
Full-Scale Validation of Stress Prediction Models for Flexible Pipe Foldless End Fitting Anchoring System
Authors: Gallina Alessandro , Rigon Henrique Chiaradia , Geusti Lucas Alban , Wallauer Frederico , Bertoni Fabiano , Clevelario Judimar de Assis
Published: September 2023

This article presents a validation analysis of analytical and numerical models that predict the stress distribution of flexible pipe tensile armor wires at the pipe body and inside the end fitting anchoring chamber when under axisymmetric loads. It validates the method and the properties of materials and interfaces obtained using standard and customized small-scale tests. Results from an analytical model and a simplified finite element model of a foldless end fitting are compared against stresses measured in the tensile armors of a full-scale flexible pipe sample submitted to internal pressure and axial tension loads. This analysis is part of an ongoing qualification program for a foldless end fitting for offshore flexible pipes that simplifies the assembly procedure by eliminating the folding process of wires and improving its performance when under dynamic loads by reducing the stress concentration factor at the end fitting anchoring entrance.

The stress profile induced on the tensile armor wires inside the end fitting differs from the one found in the pipe body due to the gradual load transfer from the wires to the epoxy resin as well as a change of the armor geometry inside the anchoring chamber. The tensile armor stress is often used as a critical parameter in design methodologies for the anchoring system, where validated models predict the stress distribution along the wire as a function of pipe layers geometry, disposition of wires embedded in resin inside the anchoring chamber, material, and interface properties. These models can predict the anchoring system maximum load capacity and stress concentration factors induced in the wires at end fitting entrance.
Comparative Study for Numerical Modelling and Analysis of Floating Offshore Wind Onsite Installation
Authors: Hong Sunghun , Yuan Shuai , Zhang Houxiang , Halse Karl Henning
Published: September 2023

This paper discusses an onsite installation method that involves the direct installation of a wind turbine at an offshore operating site. Since a fully assembled wind turbine is lifted and installed on a spar foundation at the operational site, complex responses are expected due to the multibody system of the installation vessel, the lifted wind turbine, and the spar foundation. To verify the reliability of the numerical results of the proposed alternative installation method and to gain a better understanding of the system dynamics, the installation system was modeled using SIMO and OrcaFlex, and the numerical results were compared. The comparative study was conducted in the following steps: 1) eigenvalue/modal analysis, 2) RAO verification and comparison, and 3) dynamic analysis and comparison. The results obtained in this study can be utilized in the design system components such as installation vessels, floating foundations, mooring systems, mechanical dampers, lifting devices, and control systems.
Simulations of Complex Offshore Problems Using GPU-Accelerated Near-Far Field Coupled Model
Authors: Lu Xin , Dao My Ha , Le Quang Tuyen
Published: September 2023

A fully nonlinear near- and far-field coupling numerical model is used for numerical simulations of the wave-current-structure interaction, with specific applications to the marine offshore floating structures. For a better efficiency, a GPU-accelerated high-order spectral (HOS-CUDA) solver is used to simulate the wave propagation and interaction with current in the large far field. In the small near field an incompressible multiphase flow solver with free surface capture scheme from the OpenFOAM library is adopted to solve the nonlinear wave loads and seakeeping response of the structure. The near and far field coupling model is applied to simulate the seakeeping response of a self-propulsive ship hull in head wave conditions. In addition, the model is used to simulate a more complex scenario where two moored floating offshore wind-turbines are considered.
To Improve the Orientation of a Jetty Exposed to Swell and Current to Minimise Operational Downtime
Authors: Eggermont Coen , van Deyzen Alex
Published: September 2023

For a jetty exposed to waves it is important to understand the behaviour of the moored ships and the operational downtime in early stages of the development to determine if the proposed terminal meets the downtime requirements. In case of steep depth contours, a breakwater is not a cost-effective solution to reduce the operational downtime. Other solutions to reduce the downtime to acceptable levels are required.

This paper shows, for a location with strong currents parallel to the coast but also with a predominant swell at a 45° angle with the coast, how numerical modelling of the moored ship response can be used in an early stage to optimize the orientation of the jetty with the aim to minimize the (annual average) downtime. The downtime has been determined based on the behaviour of moored tankers for five different jetty orientations.

The orientation which leads to the least amount of downtime, is an orientation more in line with the swell wave direction. For this location, the effect of current on the downtime is less dominant for the relevant sizes of tankers than the effect of swell waves.

This paper shows how numerical modelling of the moored ship response can provide the required insight in the operational downtime in an early stage of the development of a jetty exposed to waves, which in turn can be used minimize the operational costs.
A Practical Approach for Wave Loads on Bilge Keels in Irregular Seas
Authors: Xia Jinzhu , Liu Huaxing , Sukri Hilmi
Published: September 2023

A probabilistic approach is proposed to derive the design wave loads on bilge keel structures in irregular seas. An equivalent drag coefficient is introduced to account for both drag and inertia contributions in the wave loads. For each irregular sea state, the most probable maximum (MPM) value of the wave load is expressed in terms of the equivalent drag coefficient and the MPM value of the relative flow velocity. A generalized Keulegan-Carpenter (KC) number is also introduced in terms of the MPM value of the relative flow velocity and the associated mean up-crossing period of the relative velocity, which can be directly obtained from 3D diffraction analysis. The KC-dependent equivalent drag coefficient is determined by fitting a modified hyperbolic relation to the values derived based on the total wave load measurement from the model tests in irregular sea states of a Floating Production Storage and Offloading (FPSO) system design. The proposed new approach involves the application of an equivalent drag coefficient for each irregular sea state specified in the metocean report for FPSO design. The wave load formula is directly applicable for calculating short-term extreme wave loads for ultimate strength design. A 2-parameter Weibull distribution is found to fit well the measured short-term wave load distribution. The long-term probabilistic load distribution for fatigue design can be developed by summing the short-term distribution of each sea state weighted by the probability of occurrence. Thus, efficient, frequency-domain wave load calculations can be performed for both ultimate and fatigue state designs of the bilge keels. A practical application is presented of the proposed approach to a deep water Brazilian FPSO project.
Simulation and Characterization of Low-Frequency Flow Oscillations Over a Symmetrical Sail at Large Attack Angles for an Unmanned Sailboat
Authors: Zeng Qingsong , Cai Wei
Published: September 2023

Unmanned sailboats harvest wind energy as their main thrust power. This ability makes them outstanding for continuous marine hydrometeorological research on open seas. Different from airplanes, where small attack angles are generally used to avoid a stall, sailboats typically sail with large attack angles (more than 20 degrees) in downwind conditions. Although stall happens and the lift drops dramatically, the drag now acts as the main contributor to thrust. However, at low Reynolds numbers (around 10^5) and large attack angles, low-frequency flow oscillations would be easily triggered by vortex shedding. Such periodic or quasi-periodic aerodynamic forces would cause an undesirable change at the moment, which would result in large force fluctuations and random behaviors of the sail. In this study, LES simulations are carried out at Reynolds number 3.6E5, with the attack angle varying from 5 to 90 degrees for a 3D NACA0012 sail. Validation is performed at the same Reynolds number using experimental data. The influence of turbulence intensity is also explored. The results show that the wiggles of both lift and drag coefficients increase with the attack angle. The fully separated flow will form a recirculating flow region on the low-pressure surface of the sail, which triggers vortices at different scales. The flow lacks enough energy to keep a fixed shape, and the vortex shedding causes variations in the pressure leading to oscillations in the lift and drag. The dominant frequency locates in the range of 0.5–10Hz, which straightforwardly indicates a low-frequency oscillation. It also shows that a change in attack angle will alter the frequency of the low-frequency oscillations. Designers of the unmanned sailboat should keep this information in mind when determining the attack angle in a specific condition.
Buoyant Miscible Jets in a Viscoplastic Medium With Applications in Plug and Abandonment of Oil and Gas Wells
Authors: Hassanzadeh Hossein , Joshi Saptarshi , Akbari Soheil , Taghavi Seyed Mohammad
Published: September 2023

Plug and abandonment (P&A) is the final stage in the lifetime of oil and gas wells, during which the well is properly sealed to prevent fluid movements between different layers. The main steps of P&A include accessing the annulus section, cleaning the target area, and installing the cement plug barrier. Jet cleaning is an efficient technique for the second step of P&A, in which a heavy fluid is injected to displace lighter undesirable fluids. It is crucial to understand the effects of fluid properties on the jet cleaning process to achieve efficient cleaning. This study focuses on the jet flow dynamics in a miscible buoyant jet, where a Newtonian fluid is discharged through a circular nozzle into a viscoplastic ambient fluid. The effects of different parameters on the jet flow behaviour are analyzed, including the injection velocity and the yield stress of the ambient fluid. The buoyant jet flow behaviour is characterized using various jet features, including the laminar length and the penetration length. Our results show that the yield stress of the ambient fluid resists the jet evolution, decreases the jet penetration length, and changes the laminar length variation.
Environmental Loading on a Concrete Gravity-Based Offshore Structure in the Presence of Freak Waves and Currents
Authors: Zaman M. Hasanat , Akinturk Ayhan
Published: September 2023

There has been a rise in oil and gas industry activity in the offshore area of the North Seas as well as in other parts of the world. Operating offshore fixed and floating structures in such areas come with additional menaces due to the coexistence of large waves and strong currents and their consequent interactions. The effects of strong currents and large waves that move through the area may seriously impair the functionality and safety of these offshore structures, particularly when a large wave travels against a strong current since this could produce extremely high waves. In this study, the loadings of such a strong wave-current coexistence field on a concrete gravity based structure (GBS) are described both on its shaft and topside. The simulations use a 3D mass, momentum, and energy balanced model as numerical tools for predicting loads on the structure. Using mass, momentum, and energy flux conservation equations, the proposed 3D numerical model is formulated that describes the characteristics of the wave-current coexistence field. To study a variety of scenarios, incident wave and current conditions are systematically changed in the simulations. The local still water depth and the geometry of the GBS were maintained constant. The shaft has a diameter of 30m, and a length of 95m and the topside has a dimension of 50m towards incident wave direction, 75m in length, and 2m in depth. The still water depth is taken as 80m, and the estimated air gap is 15m. In each situation, the simulation lasts for three hours.

The new data and information that would be generated as a result of this effort may be vital for potential inclusion in the GBS design process and hence improve structural and operational safety in the severe and wave-current coexistence environment.
Erosion-Corrosion of Steel Structure Caused by Friction of Sea Ice Based on Simple Experiment and Theory
Authors: Kioka Shinji , Takeuchi Takahiro
Published: September 2023

In this study, we focused on the corrosive wear, assuming that the frequent removal of rust layers by sea ice friction may accelerate corrosion. We performed simple experiments on repeated removal of rust layers on a metal material surface by an artificial method to simulate the rust removal caused by friction with sea ice, and developed a simple calculation model for corrosion progression based on diffusion-controlled process of oxygen under the formation of corrosion film. We found that structural steel further corroded with an increase of the removal frequency of corrosion film, and that corrosion progression did not depend on hysteresis and previous removal frequencies of corrosion film, provided each exposure time under the formation of corrosion film is the same. The calculation model showed that corrosion progresses linearly with a square root of time, and also agreed with such experimental trends. Tangent line of the progress curve of corrosion at the time of zero by the model also agreed well with the experimental results with high removal frequencies, which indicates the validity of the model. We demonstrated conceptually corrosion processes depending on contact frequencies of sea ice with steel structure, and added considerations for practical applications.
Lüders Induced Localization in Tubes Under Cyclic Bending
Authors: Zhang Weihan , Kyriakides Stelios
Published: September 2023

Preceding experiments and analyses revealed that bending of tubes whose material exhibits Lüders banding leads to the progressive nucleation of inclined bands of higher strain organized into periodic diamond clusters. The clusters cover both the tensioned and compressed sides of the tube with the affected length developing a higher curvature than the unaffected section. Between the diamond patterns are elastic zones required for each periodic domain to conform to the curvature of the tube. The present work examines how this non-uniformly deformed structure behaves under curvature symmetric cycling. A combined isotropic/kinematic hardening constitutive model that incorporates partial softening over the extent of the Lüders strain is adopted. A tube is first bent until the diamond patterns cover the whole length and in uniform curvature. During unloading and reverse bending the curvature remains uniform. The diamond patterns are gradually erased but simultaneously local secondary patterns of higher strain develop in the hitherto elastic zones between the original diamonds. When completing the cycle, the pattern evolution follows the reverse order with the secondary patterns being erased and the diamond patterns reappearing. The curvature remains uniform throughout and the evolution of local patterns develops simultaneously along the length. The paper demonstrates that the main effects of the extent of the Lüders strain and of the material yield strength are captured under monotonic bending. The behavior under curvature symmetric cycling follows broadly those of the base case outlined above.
Testing to Reveal Vertical Soil Stiffness and Damping at Pipeline Free-Span ‘Shoulders’
Authors: Papavasileiou Vasileios , Bransby Fraser , Watson Phil , O’Neill Michael
Published: September 2023

Pipeline (or cable) engineers routinely have to manage free-spans — i.e. sections of the pipeline which are or which may become unsupported by the seabed — during their operational lifetime. Free-spans can make the pipeline susceptible to Vortex-Induced-Vibration (VIV), with associated potential of fatigue failure, leading to the requirement for regular pipeline inspections and expensive free-span mitigation for critical spans. VIV can lead to significant dynamic movement of the pipelines in the free-span and requires consideration of the metocean inputs, the local hydrodynamics, seabed changes due to scour, the structural response of the pipeline and the seabed support conditions (‘pipe-soil interaction’).

Although recommended practice guidelines exist for pipe-soil-interaction of submarine pipelines, there is a knowledge gap in the realistic selection of non-linear vertical soil springs and dashpots at the free-span shoulders (i.e. sections of continuous pipeline support on either side of a free-span), which may lead to increased conservatism and potentially unnecessary remediation. This paper reports an experimental investigation into the variation of soil stiffness and damping ratio for a pipeline section on the seabed that can be idealised as a segment (representing part of the free-span shoulder) when subject to different cyclic vertical loading conditions.

Results from the tests are compared with state-of-practice guidelines, and show that both the load history and amplitude of the cyclic loading have a significant impact on the soil response. The reported results will contribute to better understanding of pipe-soil-interaction for free-span shoulders and improved selection of non-linear soil springs and dampers.
Toward Environmental and Structural Digital Twin of Offshore Wind Turbine
Authors: Zhao Xiang , Dao My Ha , Le Quang Tuyen
Published: September 2023

In the wind energy industry, a digital twin (DT) is very useful for managing the operation of a wind turbine and predicting structural health conditions in real-time as well as projections in the near future. A real-time surrogate model is a very crucial part in building a DT. Towards that end, we employ a Reduced-Order Modelling (ROM) approach to construct a surrogate model for the environment-structure system of a bottom-fixed offshore wind turbine (OWT). The entire environment-structure system is broken down into major sub-systems of wind, wave, and structure. Based on the high-fidelity Computational Fluid Dynamics (CFD) data, the wind ROM model can quickly provide the loadings on the components above water level in the parameter space spanned by the incoming wind speed, the rotational speed of the rotor, the pitch and tilt angles of the turbine. The hydro loadings on the underwater components of the OWT are solved by the empirical Morison formula. The OWT structural ROM model is component-based consisting of blades, hub, nacelle, tower, and monopile. The structural ROM model takes the loading data feeds from the wind and wave models to predict the structure responses of the OWT system, including stress. Since the DT is constructed via the component-based, it can also be used to play out “what if” scenarios when there are component level changes. For instance, the model can predict the system response of OWT when certain parts undergo structure failures. Benefiting from the cost-efficient ROM models, the DT is over two orders of magnitude faster than high-fidelity simulations while maintaining good accuracy.
Design Drivers for Pre-Lay and Recovery Installation of Deep-Water Steel Lazy Wave Riser Systems
Authors: Sebastian Abhilash A. , Jeon Jaehyeuk , Patel Vikas , Lal Mayank
Published: September 2023

Wet storage of risers prior to installation on the vessel is generally done to make the installation schedule more flexible, especially in harsh environments with a small weather window. The wet storage of flexible, umbilical, or traditional steel catenary configuration has become quite common. However, more steel lazy wave riser systems (SLWRs) are increasingly being wet stored in recent projects.

This paper will present an installation and wet park example study of an SLWR riser system at 7000 ft water depth. The major design drivers and technical challenges involving wet park configuration, laydown, recovery, and transfer during installation are discussed. The steel lazy wave riser wet park stability and fatigue and transient response of wet-parked risers during flooding and dewatering are evaluated from an analytical aspect. The riser wet park stability and fatigue, consist of clashing checks, extreme strength, and vortex-induced vibrations (VIV) fatigue during the duration of wet park.
Hydrodynamic Damping of a Riser Oscillating in an In-Line Steady Current at Low Keulegan-Carpenter Numbers
Authors: Peng Peng , Liu Kun , Wang Jiaxia , Gao Zhenguo
Published: September 2023

Hydrodynamic damping is key to the fatigue design of risers whose dynamic responses are controlled by the wave induced vessel motions. The effect of in-line steady current on the hydrodynamic damping is not fully understood and the prediction of hydrodynamic damping of a riser at low KC with the relative velocity Morison equation raises concerning for overestimation, which may result in overestimation of fatigue life in design. In this paper, the hydrodynamic damping of a circular cylinder oscillating in an in-line steady current is investigated based on the 2D direct numerical simulation (DNS). The Stokes number is 20950 while the KC is in the range of 0.4 ∼ 4.9 in the numerical simulation. The drag and added mass coefficients from the numerical simulations agree well with those from the experimental measurements at the same Stokes number and KC values. Different steady current velocities are considered in numerical simulations to demonstrate the effect of in-line current on the hydrodynamic damping of the oscillating cylinder. The appropriateness of using relative velocity Morison model for prediction of hydrodynamic damping with an-line steady current is examined by analyzing the in-line hydrodynamic force. The effect of the steady current on the vortex shedding of the oscillating cylinder is investigated to give an insight of the flow field characteristics.
On the Gaussianity of Wind and Wave Field Data
Authors: Laface Valentina , Arena Felice
Published: September 2023

This work deals with an analysis of simultaneous wind and wave records collected at Natural Ocean Engineering Laboratory (NOEL) of Reggio Calabria, Italy. NOEL is a field laboratory located in the Messina’s Strait which is characterized by particular wind conditions that generate sea states representing small scale models of typical ocean storms. Wind data are collected by an anemometer located on a nearshore platform at 5 meters height above mean water level recorded with a frequency of 4Hz. Sea surface elevation is recorded by ultrasonic probes at intermediate water condition with a frequency of 10Hz. Wind data are provided in terms of wind speed fluctuations, while wave data in terms of sea surface elevation. Over time intervals compatible with the stationarity assumption, both wind speed fluctuations and sea surface elevation are represented by a gaussian process characterized by a given frequency spectrum. However, real data exhibit significant deviations from gaussian distribution. This work is focused on the analysis on whether wind and wave records are gaussian or not, elucidating analogies and differences between wind and wave processes. Results show that both wind and waves are asymmetric and non-linear. Waves are right skewed, having crests greater than troughs, while wind speeds fluctuations may be both right and left skewed, revealing that peak amplitudes can be larger than lulls and vice-versa. Deviation from gaussianity for wind speed can be larger than for waves.