bluuebunny/crossref_metadata_2025 huggingface dataset:
Bayesian Updating of Estimated Parameters Representing Multi-Modal Directional Wave Spectrum Using Measured Ship Hull Stresses
Authors: Kubo Hiromi , Okada Tetsuo , Chen Xi , Kawamura Yasumi , Mitsuyuki Taiga , Hayakawa Ginga
Published: September 2023

To ensure structural safety of large container ships, advanced application of monitoring data is pursued. To estimate sea state in a probabilistic manner, in this paper, we attempted peak-by-peak Bayesian updating of the multi-modal directional wave spectrum estimated using the measured ship hull stresses. In addition, time history of the probability distributions of stress responses according to the obtained probabilistic sea state was discussed compared with the measurement.
Hydrodynamic Forces on Near-Bed Cylinders in Steady Currents
Authors: Hu Xiaoyuan , Cheng Liang , Tong Feifei , Teng Yunfei , Qu Yan , Jiang Hongyi
Published: September 2023

Numerical simulations are carried to investigate hydrodynamic forces and flow patterns around cylinder clusters of equally-spaced tandem cylinders closed to a plane wall in steady flow. The Reynolds number covered in the study are Re = 10000 and 200000. The number of cylinders in the cluster are 2, 3 and 6 with the spacing between the cylinders being 1, 2 and 4 and the gap to diameter D ratio (e/D) ranging from 0.1 to 1. The numerical results show that the sheltering effect of the leading cylinder in the cluster leads to significant reductions of hydrodynamic forces on the downstream cylinders in the cluster, for the parameter ranges considered in this study. A methodology based on the combination of low fidelity computational fluid dynamic simulations and reliable published force coefficients is proposed for estimating hydrodynamic forces acting on individual cylinders in the cluster.
Motion Suppression of a Floating Offshore Wind Turbine Using Heaving Point Absorbers: A Case Study in Australia
Authors: da Silva Leandro Souza Pinheiro , Y. Sergiienko Nataliia , S. Cazzolato Benjamin , Meng Fantai , de Oliveira Marielle , Ding Boyin
Published: September 2023

Hybrid platforms composed of a floating offshore wind turbine (FOWT) and heaving point absorbers (PAs) can be a promising solution to reduce project costs while improving the quality of energy and ocean space utilisation. Although this hybrid platform idea is attractive, wave energy converters (WECs) may transfer part of their energy to the FOWT via motion if the devices and their respective power-take off (PTO) systems are not properly designed, leading to undesirable loads. Based on that, an alternative option is the use of WECs to reduce the FOWT platform motions, while absorbing wave energy. This approach is particularly important in locations where both resources are abundant, such as in Australia, where the hybrid solution may extend the platform’s lifetime. In this general context, this work aims to investigate the use of PAs as a motion suppression device. The hybrid platform is assumed to be subject to realistic environmental conditions: turbulent wind (temporal and spatial effects) and irregular waves. The numerical model is built in the frequency domain, and important sources of nonlinearities are estimated using statistical linearisation. The performance of the hybrid platform is compared against the standalone FOWT for an offshore site in Sydney, Australia. Results demonstrate that depending on the PTO configuration, the hybrid platform has a superior response compared to the standalone FOWT, suppressing the horizontal nacelle acceleration by around 8% while extracting an additional 30 kW from waves.
Analysis of Turbulence Parameters for a Tidal Energy Site in a Wave-Current Environment
Authors: Tan Tian , Venugopal Vengatesan , Sellar Brian
Published: September 2023

Tidal power converters deployed in areas where waves and tidal currents coexist face high levels of turbulences, which can lead to unstable power generation and increase the risks of turbine blade fatigue failure. In order to improve the design and safety operation of tidal turbines in a combined wave-current environment, it is necessary to understand and characterise the turbulence parameters such as turbulence intensity (TI)/turbulent kinetic energy (TKE) etc. It is also important to characterise how waves and currents separately affect these parameters.

In this study, field data collected by an Acoustic Doppler Current Profiler (ADCP) at the Pentland Firth, Orkney Islands, Scotland, are analysed to evaluate the levels of TI produced separately by waves and tidal currents. The empirical mode decomposition (EMD) method has been utilised for this analysis. At first, using the EMD, the velocity components corresponding to waves and tidal current components are separated. In order to verify the separation methodology, a two step process is adopted. In step one, wave component velocities are converted to significant wave heights using linear wave transfer function. For the second step, the significant wave heights obtained from step one are compared with the same hindcast by a coupled wave-current numerical model. A very good match between wave heights is observed with a correlation coefficient of 0.8, thus validating the methodology followed. Then, the depth-varying vertical profiles of the turbulence intensity (TI) of the decomposed wave and current components are calculated. It is found that the streamwise wave-induced TI is about 5% at the height of 15m where the turbine hub is placed, while the tidal current-induced TI is 10%–17%. The wave-current combined TI is 13%–20%. This study has demonstrated a methodology to successfully separate and quantify turbulence intensities produced individually by waves and tidal currents when they coexist at a site.
Deepwater RCM and SRI Design of Production Rigid Flowline Loops
Authors: Chatzimanolis Nikolaos , Jalali Hossein , Bedrossian Arek , Xie Min , Lewis Mark
Published: September 2023

Deepwater High Pressure High Temperature (HPHT) rigid flowlines laid on large slope seabed morphology, with complex operational loading and multiple subsea well tie-in locations, impose significant design challenges. This paper presents a novel thermomechanical design for production flowline loops which involves the deployment of deepwater Residual Curvature Method (RCM) and Subsea Rock Installation (SRI). It focuses on the RCM engineering which ensures that the design satisfies all the criteria for any as-landed angle of the RC sections; i.e. irrespectively of the level of rolling of the RC sections during installation. This design accounts also for the effect of the cooldown of thick insulated flowlines, on the seabed just after pipelay from as-laid to ambient seawater temperature, on their response. The effects of soil berms on the initial formation and through-life performance of the lateral buckles at RC sections are discussed. Moreover, the design accounts for the through-life response of the engineered lateral buckles at locations of relatively high transverse slopes. Furthermore, the reliability of the RCM is demonstrated with a deterministic approach. Additionally, this paper presents a comparative study which demonstrates the lower carbon footprint of RCM relative to that of sleepers. Finally, the paper discusses the deployment of SRI to partially restrain the flowlines and control their axial displacements at critical locations to acceptable levels.
A Dynamics Experiment With a Submerged and Suspended Vertical Riser Pipe Small Scale Model Undergoing Forced Motions at the Top
Authors: Cesar de Oliveira Trigo Caio , Bordalo Sergio Nascimento , Morooka Celso Kazuyuki
Published: September 2023

The present work describes a laboratory experiment with a small scale model of a vertical marine riser with a free lower end and with forced motions at the top end, inside a water tank. Long and slender flexible vertical riser pipes are very common in offshore operations. They are used in drilling rigs for re-entry operations in subsea petroleum wellbores, they are employed to elevate cold water from the deep ocean in order to refrigerate equipments in the floating petroleum production facility at the sea surface, among other purposes, and they are also used to lift mineral slurry mixtures in seabed mining operations.

In the present experiment, the transversal movements of the model along its length were recorded over time. This paper describes the experimental set-up and the optical measurement system developed to obtain the model’s displacements. The challenges and solution to find a satisfactory material for the pipe model are commented and the design of the small scale model is discussed. Numerical simulations for the model’s vibrations were computed to evaluate the measurement results. Advancements were developed for the experimental procedure and modeling, including the testing mechanism and the instrumentation to measure the main parameters of the dynamic behavior of the vertically suspended and submerged flexible pipe model.

The experimental method used herein could be extended to other configurations and conditions with the proper scaling and design of the physical set up, and consequently be applied to various offshore operations dealing with the exploitation of natural resources and energy of the oceans.
Hydrodynamic Forces Acting on Small-Diameter Pipelines Under Combined Irregular Wave and Current Flows: A Case Study
Authors: Teng Yunfei , Chen Zhanjie , Griffiths Terry , An Hongwei , Draper Scott , Mohr Henning , Cheng Xin , Hu Xiaoyuan , Cheng Liang
Published: September 2023

The hydrodynamic forces induced by combined irregular waves and currents acting on a small-diameter pipeline are investigated based on some physical tests. The results suggest that the Morison equation leads to poor predictions of the time-variant forces when the pipeline is mounted on the bottom. For the on-bottom cases, the method suggested by Jacobsen et al. (1988) is demonstrated to work better than the traditional Morison equation. However, the Morison equation performs reasonably well on describing the temporal forces when the pipeline is far away from the seabed.
Wave-Induced Loading Simulation for a Semi-Submersible FOWT Platform Using CFD-SWENSE Coupled Solver
Authors: Shen Cong , Chen Nian-Zhong
Published: September 2023

The low-frequency wave-induced loading on semi-submersible floating wind turbines is normally small, but the loading can result in large motions due to resonant responses in surge and pitch. Therefore, one of the most important concerns regarding the numerical simulation of wave-induced loading on floating wind turbines is how to accurately predict the difference-frequency wave-induced loading, especially near the resonance frequencies. The potential flow method based on the Morrison formula cannot consider the fluid viscosity, and thus the numerical accuracy of the prediction of wave-induced loading is generally insufficient, and usually underestimating the highly nonlinear difference-frequency wave loading. Navier-stokes equation based the computational fluid dynamics (CFD) method has shown the merit for improving the numerical prediction of nonlinear wave-induced loading and motions of offshore floating structures, however, the computational cost of the CFD method is too expensive as a higher-fidelity modeling tool, which is not suitable for engineering application at the current stage. This paper aims to establish a CFD-SWENSE (Spectral Wave Explicit Navier-Stokes Equations) coupled solver to solve this problem but maintaining sufficient numerical accuracy. The potential part (the incident waves) is solved with the spectral wave model. The viscous part (the complementary perturbation on the incident waves) is solved with the CFD solver. Based on this potential viscous flow coupled solver, the differential frequency of wave loading of a semi-submersible floating body under the influence of bichromatic waves is investigated. The results show that the computational efficiency of the coupled solver is improved compared with the CFD method, however, the wave-induced loading predicted by the coupled solver is in good agreement with that predicted by the CFD method.
Validation of CFD-Based Numerical Wave Basin for a Floating Offshore Wind Turbine in Irregular Waves and Dynamic Wind
Authors: Jang Hyunchul , Jang Hakun , Teng YihJeng
Published: September 2023

Several recent benchmark studies have demonstrated that Computational Fluid Dynamics (CFD) is capable of capturing both nonlinear and viscous effects in marine hydrodynamics and predicts wave- and current-induced offshore platform motions accurately. A CFD-based numerical wave basin developed by Technip Energies, MrNWB [1, 2], has been well-validated against physical model test results for various offshore floating platforms including a floating offshore wind turbine in National Renewable Energy Lab (NREL)’s OC6 CFD JIP [3]. However, the OC6 CFD JIP focused on the motion responses corresponding to hydrodynamic loadings only.

In the present study, a new coupled analysis methodology is introduced to accurately predict the motion responses of a floating offshore wind turbine considering wind turbine. In the present coupled analysis, aero-servo-elastic behaviors of the wind turbine blade and tower are simulated by OpenFAST [4], and the hydrodynamic loads on the floating platform and mooring system are simulated by Technip Energies’ CFD-based numerical wave basin tool, MrNWB. For the fully coupled aero-hydro-servo-elastic simulation, the OpenFAST dynamic solver calculates the system responses of floating offshore wind turbine, and the hydrodynamic loads on the floating substructure are integrated into the CFD solver with respect to the 6-DOF platform motions. This new coupled analysis tool is called Wind Turbine Numerical Wave Basin (WTNWB).

This paper presents validation of WTNWB for the DeepCWind semisubmersible model tests in irregular waves and a steady wind condition. The validation results are systematically compared with model test results [5, 6] and show good agreement.
Experimental Evaluation of Supercritical CO2 Enhanced Oil Recovery and Storage Capacity Using Dual-Core Core Flooding Technology for Carbonate Reservoirs
Authors: Zhou Xianmin , Yu Wei , Kamal Muhammad Shahzad , Wu Yu-Shu , Khan Sarmad Zafar , Al-Abdrabalnabi Ridha
Published: September 2023

The depleted oil reservoirs are considered as the potential geological storage site for CO2, which is one of the solutions to carbon emissions and the increased temperature in the atmosphere. The geological properties of the depleted oil reservoir, such as reservoir heterogeneity, directly affect the amount of CO2 storage. Unfortunately, no research has been done on this topic. In this study, we experimentally studied the effect of reservoir heterogeneity on oil recovery factors in cases of seawater flooding and supercritical CO2 (sc-CO2) miscible injection and the resultant sc-CO2 storage in depleted oil reservoirs at the end of the oil field development.

A dual-core flooding experiment involving two reservoir carbonate core samples with different permeabilities and porosities was carried out using live oil, which is that gas dissolves in the crude oil as the displaced phase. Seawater and sc-CO2 as the displacing phases were used to conduct water flooding and the miscible injection process under reservoir conditions (overburden pressure of 4,500 psi, pore pressure of 3,200 psi, and reservoir temperature of 102°C), respectively. The scCO2 miscible injection process was followed by seawater flooding to recover the remaining oil after seawater flooding and evaluate the storage capacity of sc-CO2.

From the results of this study, it was found that sc-CO2 miscible injection following seawater flooding can recover additional oil, which is related to the properties of rocks. We also found that high-permeable rock has a significant potential for scCO2 storage compared to low-permeable rocks. In addition, the effect of reservoir heterogeneity on the injectivity of sc-CO2, permeability loss, and scCO2 storage efficiency is-also discussed.
Autonomous Port Navigation With Ranging Sensors Using Model-Based Reinforcement Learning
Authors: Herremans Siemen , Anwar Ali , Troch Arne , Ravijts Ian , Vangeneugden Maarten , Mercelis Siegfried , Hellinckx Peter
Published: September 2023

Autonomous shipping has recently gained much interest in the research community. However, little research focuses on inland - and port navigation, even though this is identified by countries such as Belgium and the Netherlands as an essential step towards a sustainable future. These environments pose unique challenges, since they can contain dynamic obstacles that do not broadcast their location, such as small vessels, kayaks or buoys. Therefore, this research proposes a navigational algorithm which can navigate an inland vessel in a wide variety of complex port scenarios using ranging sensors to observe the environment. The proposed methodology is based on a machine learning approach that has recently set benchmark results in various domains: model-based reinforcement learning. By randomizing the port environments during training, the trained model can navigate in scenarios that it never encountered during training. Furthermore, results show that our approach outperforms the commonly used dynamic window approach and a benchmark model-free reinforcement learning algorithm. This work is therefore a significant step towards vessels that can navigate autonomously in complex port scenarios.
High-Order Phase-Resolving Method for Wave Transformation Over Natural Shorelines
Authors: Tsao Wen-Huai , Schurr Rebecca , Kees Christopher E.
Published: September 2023

The use of nature-based facilities has become a popular solution to coastal hazard mitigation and shoreline stabilization. Emergent vegetation, such as mangrove forests, has been proven an effective protective system for alleviating wave and surge impact during a tsunami or tropical cyclone event. To reduce the quantification work and uncertain parameterized equations when modeling the wave height attenuation and momentum dissipation through emergent marsh vegetation, a new approach for implementing a high order Cut Finite Element Method (CutFEM) for problems with embedded solid structures in viscous incompressible flows is presented. The CutFEM allows using the same number of degrees of freedom as the underlying conforming Galerkin method on the fixed background mesh, which is independent of the configuration of non-conforming interfaces. Therefore, it has the same element assembly structure as classical FEM on the background mesh. No explicit generation of cut cell meshes, adaptive quadrature, or local refinement is required. The idea of equivalent polynomials is also adopted to compute the exact integration involving products of polynomials with Heaviside and Dirac distributions. Therefore, this method gains high-order accuracy for embedded interfaces and robustness of the signed distance representation in the level set field. The numerical method that uses a physical model of mock-up mangrove forests is validated through the wave flume experiment conducted by Kelty et al. at OSU. The correlations between the numerical results and experimental measurements are presented. All numerical simulations are completed by the open-source toolkit Proteus.
Analysis of Convergence Behavior for the Overset Mesh Based Numerical Wave Tank in OpenFOAM
Authors: Chen Hao , Qian Ling , Cao Deping
Published: September 2023

This paper presents a solution verification and validation study for an overset mesh based numerical wave tank in Open-FOAM, which considers the coupling between a free-surface hydrodynamic flow model, a rigid body motion model and an overset mesh. The coupling between the rigid body motion solver and the free surface flow solver was achieved in a segregated manner. Free decay of roll motion of a barge was modelled using the numerical wave tank, and the damping coefficient was selected as the target quantity for solution verification. The least square based solution verification procedure was adopted, where one of the four types of error estimators was fit to the data in the least-square sense. Both structured and unstructured mesh were tested, and their effects on the convergence order, numerical uncertainty and error were carefully investigated. From the numerical tests, it is found that the numerical wave tank exhibits a very good convergence property for the floating body problems with structured mesh, i.e. nearly second order in space and first order in time. However, when switching the body-fitted mesh to unstructured mesh, the grid convergence is reduced to first order. Unstructured mesh does not significantly affect the convergence order in time domain, but results in a larger uncertainty due to data scattering.
Dynamic Response of a Taut-Moored Floating Oscillating Water Column Wave Energy Converter in Extreme Waves
Authors: Gubesch Eric , Abdussamie Nagi , Penesis Irene , Chin Christopher
Published: September 2023

This paper presents the results of an experimental investigation into the dynamic characteristics of a 1:36 scaled Oscillating Water Column (OWC) Wave Energy Converter (WEC). Two mooring configurations were tested, namely a vertical taut mooring (i.e., tension leg) and a taut mooring with 45° tendons. The tested sea state was based on conditions that were observed during Tropical Cyclone Oma in 2019 and was re-generated in the physical wave tank with NewWave theory. The orifice used to model the OWC’s power take-off system during operational sea states was closed to simulate the WEC in the shut-down condition. Detailed analysis included the OWC WEC’s rigid body motions (i.e., heave, surge and pitch), OWC chamber pressures, and mooring/tendon tensions. The model with both mooring configurations was found to exhibit similar heave motions, however the tension leg mooring demonstrated a larger surge response whereas the 45° taut configuration demonstrated substantially larger pitch rotations. Mooring lines/tendons in both mooring configurations experienced similar maximum tensions, however the occurrence of peak loads relative to the mooring configuration tested could take place in the forward or aft moorings. For instance, the forward moorings of the 45° taut configuration produced an average peak tension of 79.640 N, whereas the aft tendons for the tension leg configuration produced an average tension of 80.725 N. The load distribution between the forward and aft moorings for the tension leg configuration was similar and showed a difference of 8.3%. However, a much larger variation was observed with the 45° taut configuration where a 39.7% reduction was observed between the forward and aft moorings. Finally, a very high-frequency response was observed in the time history (during and post wave impact) of both the forward and aft tendons of the tension leg mooring configuration. Interestingly, the high frequency response was not observed in the 45° taut configuration.
A Risk-Based Fire Protection Design of a LNG Fueled Ship
Authors: Kim Hyunpyo , Nam Hyunjoon , Kang Ga Hyeong , Kim Min Joo , Kim Sunghee , Shin Dongkyu , Park Sung-In
Published: September 2023

Due to cryogenic and flammable nature of LNG, the LNG-fueled ships require the risk assessment for the safety designs against the release of LNG during operation. Fire is a major accident resulting from LNG leak and the rational fire protection can be achieved by considering the probability and consequence of fire, i.e., the risk of fire. However, the current fire protection of the LNG-fueled ship depends on the prescriptive approach and this may lead to an unreasonable design of the ship. The validity of the fire protection requirement has been questioned and this paper proposes the need for the risk-based design approach. An LNG-fueled product carrier is developed and uncertainty on the interpretation of a part of the fire protection requirement in the design standard is discussed. Using a quantitative assessment technique, a fire risk is estimated and the results are presented through a risk contour which is expressed as a combination of a specific fire intensity and frequencies of fire occurrence. As the result of the risk assessment study, an affordable fire protection design is adopted and the findings of this paper are summarized in relation to the needs for the risk -based fire safety design of the LNG-fueled ship.
Optimised Wave-by-Wave Prediction of Spread Waves: Comparison With Field Data
Authors: Hlophe Thobani , Taylor Paul H. , Kurniawan Adi , Orszaghova Jana , Wolgamot Hugh
Published: September 2023

Real-time forecasting of ocean surface waves can be beneficial for many offshore operations such as ship navigation, load mitigation on floating offshore wind turbines, and control of wave energy converters. This study validates a linear, algebraic prediction model for sea states with large directional spreading. The model decomposes observed time histories using a Fourier transform to obtain an approximate representation of the wave field using a small number of directional components. Pre-processing involves the partial removal of nonlinear harmonics by a bandpass filter followed by the attachment of a NewWave-type signal at each end of each record. The model is tested using field data measured using a small array of wave buoys deployed in the Southern Ocean off Albany, Western Australia. It shows good agreement between prediction and target time series. Aggregating and weight-averaging multiple predictions obtained with different sets of optimal representative directions improves the quality of prediction. Based on the linear propagation of representative directional Fourier components, the model is relatively robust to the presence of (unfilterable) higher harmonics and fast enough for real-time predictions.
Detection of Long-Term Changes in Mooring Stiffness Using Vessel Position Monitoring
Authors: Eassom Adrian , Jayasinghe Kanishka , Thomas Clare
Published: September 2023

In recent years there has been a growing appreciation in the offshore sector of the importance of developing reliable and robust methods to continuously monitor the integrity of floating production system moorings. Development efforts have mainly focused on detecting mooring failures which result in changes in the behaviour of the floating structure within a short time scale. However, these monitoring system technologies can also be leveraged to detect degradation in mooring system performance over longer time scales. The stiffness of a mooring system can be influenced by several factors including creep of synthetic rope, damage to rope construction, interlink wear of mooring chain, seabed trenching of mooring lines, excessive marine growth and loss of clump weights on mooring lines. Such changes in stiffness can change the dynamic response of the floating structure, potentially increasing the offset in extreme sea states beyond the allowable design offset limits.

Hardware that measures mooring line loads or departure angles as a direct means of monitoring for mooring line failures can also be used to detect changes in mooring line pre-tension and therefore monitor for long-term changes in mooring stiffness. However, such hardware (load cells, inclinometers, sonar systems, strain gauging, etc.) can be expensive to retrofit, costly to maintain and suffer from long-term reliability issues. This has led to the implementation of solutions using Global Navigation Satellite System (GNSS) vessel position data as a more cost-effective and reliable alternative for real-time mooring integrity monitoring. There are multiple methods by which a GNSS-based integrity monitoring system can be programmed to detect mooring failures, most commonly by employing machine learning models. This paper presents a method to extend a machine learning model used for a GNSS-based integrity monitoring system to also monitor for changes in mooring system stiffness, by leveraging the use of a digital twin and assessing long-term changes in measured excursions. This method will be demonstrated via a case study for a spread-moored floating facility.
Application of Insulated Drill Pipe to Supercritical/Super-Hot Geothermal Well Drilling
Authors: Kohei Ajima , Naganawa Shigemi , Bjarkason Elvar Karl
Published: September 2023

In Japan, a research and development project is ongoing that is aimed at developing supercritical geothermal exploration and power generation methods. The extremely high formation temperatures encountered during supercritical geothermal drilling presents a challenge for the durability of downhole tools. Thus, it is essential to design an effective method of downhole cooling during drilling. To protect commonly used downhole tools from thermal damage, the objective is to reduce the downhole temperature in supercritical geothermal wells to below 175°C, which coincides with the lowest heat resistant temperature of most downhole equipment. In this study, the authors carried out numerical simulations focusing on the effectiveness of using insulated drill pipes to reduce downhole fluid circulation temperatures during drilling through formations with temperatures high enough for a supercritical reservoir. It was found that use of insulated drill pipes effectively controlled the downhole temperature by reducing the heat influx conducted from the formation. Considering the additional cost of using insulated drill pipes, we also looked at cases where the insulated drill pipes were only applied along two-thirds of the entire drillstring. Considering the flow rate of the circulating fluid and the inflow temperature, the temperature simulation was performed to keep the downhole temperature below 175°C. We also considered the additional pressure loss that could be expected from using the narrower insulated drill pipe.
Numerical Investigation of the Statistics of Vertical Bending Moments of Ships in Nonlinearly Evolving Irregular Waves
Authors: Houtani Hidetaka , Matsui Sadaoki , Fujimoto Wataru
Published: September 2023

This study investigated ship response statistics in waves evolving due to nonlinear quasi-resonant interactions. For that purpose, a nonlinear strip method, NMRIW-II (nonlinear motion in regular and irregular waves), has been extended such that nonlinear wave fields precomputed by the higher-order spectral method (HOSM) can be input. In the numerical simulation, the significant wave height and nonlinear order of the input irregular waves were varied to investigate the impact of wave nonlinearity on ship responses. Furthermore, a container ship and a wall-sided ship were used in numerical simulations to separate the nonlinearity influences attributed to the hull geometry and wave. The lengths, breadths, drafts, and water plane geometries were the same between these ships. The numerical results revealed that the body (hull-geometry) nonlinearity enhances the tail of the sagging moment peak probability distributions. Furthermore, an increase in large wave occurrence due to nonlinear quasi-resonant interaction was revealed to further enhances the tail of the sagging moment peak probability distributions.
Hydrodynamic Performance of a Conceptional Seatrain in Heading Wave Based on Small Water Plane Area Trimaran
Authors: Qin Yan , Wang Qing , Dong Guohua , Yao Chaobang , Feng Dakui
Published: September 2023

Seatrain is a new concept to reduce resistance by using a system that connects multiple ships to achieve broader ocean transportation and ocean warfare. In order to take realistic sea conditions into consideration, the hydrodynamic performance of sea train in heading wave based on multiple identical small-water-plane-area trimarans arranged in a straight line is systematically investigated in present study.

Firstly, present numerical method is validated through the comparison of computational and experimental results of a small-water-plane-area-twin-hull in waves, and good agreement can be obtained. Therefore, the resistances, heave and pitch motion of the single trimaran in wave at different speeds from 0.7m/s to 2.8m/s are obtained using STAR-CCM+. Afterward, in order to investigate the interaction of seatrain system, two or three identical trimarans are arranged in a longitudinal column navigating in regular wave. There are two approaches conducted separately, in which trimarans are physical connection or non-connection. The numerical solution is evaluated with two connection approaches and compared with single ships with the same velocity and wave condtion. The result shows that the train composing a very long, slender hull form can increase transportation efficiency and maximum speed by reducing resistance. Meanwhile, the resistance of each hull while operating as a two-ship-train and a three-ship-train is compared with hydrodynamic performance of the single ship. Through the systematic analysis, the characteristics and laws of hydrodynamic interference to minimize the collective resistance of its system are obtained.
Energy Harvesting From Multiple Responses of an Elastically Mounted D-Section Prism
Authors: Chen Weilin , Li Yuzhu
Published: September 2023

Extracting mechanical energy from flow-induced vibration (FIV) of cylindrical structures has become a critical research subject. In this paper, we numerically investigate the FIV of a D-section prism with various angles of attack (α) and look into energy harness from the identified multiple FIV responses by using immersed boundary method (IBM). We found that as α increases, six distinct responses appear. At α = 0°–40°, typical vortex-induced vibration (VIV) occurs where the amplitude first increases and then decreases with reduced velocity, showing similar behaviour to that of VIV of a circular cylinder. At α = 50°–60°, the vibration amplitude becomes larger, with a third branch observed. At α = 70° and 165°–180°, galloping response dominates where the amplitude generally increases with increasing reduced velocity. At α = 80°, a combined VIV and galloping response occurs. At α = 90°–145°, a narrowed VIV is observed where large-amplitude vibration exists in a narrowed reduced velocity range. At α = 155°–160°, the response behaves like a transition from narrowed VIV to galloping. Examinations of the energy harness from these identified responses indicate that in the VIV, energy extraction, including harness power (Ph) and efficiency (ηh), shows a strong dependence on the amplitude, while in the galloping, its dependence on the amplitude becomes significantly weak.
Proposal for How to Assess the Load Reduction Efficiency of Wellhead Load Relief Systems
Authors: Sætre Stian , Muff Anthony , Hørte Torfinn , Macke Michael , Osen Per , Reinås Lorents
Published: September 2023

Managing the risk of subsea wellhead fatigue failure has been a concern in the offshore Oil & Gas industry in the last decade. Considerable efforts have been spent towards understanding the risk picture through improving underlying analysis methodology described in recommended practices such as DNV-RP-E104.

For wells where the likelihood and consequence of a fatigue failure is viewed as unacceptably high, it may be desirable to reduce the fatigue damage for upcoming operations. This may be achieved by reducing the loads from the MODU and drilling riser to the wellhead, by using a wellhead load relief (WLR) system to reduce BOP motions.

In addition to reducing fatigue damage, WLR systems can also be designed to reduce possible accidental loading on the subsea wellhead.

The design concept of a WLR system is to transfer a major part of the riser loads into subsea facility structures and seabed, thereby reducing the residual loads into the wellhead system.

Understanding which parameters that are of importance to the efficiency of the WLR system is of essence when designing and choosing compensating measures for reducing fatigue damage.

This paper presents how to calculate the wellhead load reduction efficiency and provide guidance on properties that are of importance for the efficiency for different wellhead load relief concepts. Further, the paper will illustrate that a WLR system of high stiffness (relative to the well/BOP stiffness) will achieve a high wellhead load reduction, while a softer system results in a lower load reduction. Conversely, the load reduction for a given WLR system is less for a stiff well than for a soft well. Thus, the performance of a WLR system is impacted by relative stiffness problem and not one of stress or forces.
A Physics-Informed Neural Operator for the Simulation of Surface Waves
Authors: Sproesser Mathias Marlon , Deberaldini Netto Caio Fabricio , Marino Moreno Felipe , Fialho Coelho Jefferson , Palmiro de Freitas Lucas , Rodrigues de Barros Marcel , Cardozo de Mello Pedro , Dottori Marcelo , Gagliardi Cozman Fábio , Reali Costa Anna Helena , Costa Nogueira Junior Alberto , Satoshi Gomi Edson , Aoun Tannuri Eduardo
Published: September 2023

We develop and implement a Neural Operator (NOp) to predict the evolution of waves on the surface of water. The NOp uses a Graph Neural Network (GNN) to connect randomly sampled points on the water surface and exchange information between them to make the prediction. Our main contribution is adding physical knowledge to the implementation, which allows the model to be to be more general and able to be used in domains of different geometries with no retraining. Our implementation also takes advantage of the fact that the governing equations are independent of rotation and translation to make training easier. In this work, the model is trained with data from a single domain with fixed dimensions and evaluated in domains of different dimensions with little impact to performance. We believe this technique could be extended to more complex problems, such as simulating water currents in environments with more complicated geometries. It may also be possible to use encoding models that are aware of temporal evolution to predict a full time series instead of just a snapshot.
Numerical Simulation of a Moored Wave-Buoy in Waves and Current by Smoothed Particle Hydrodynamics
Authors: Capasso Salvatore , Tagliafierro Bonaventura , González-Ávalos Raúl , Martínez-Estévez Iván , Domínguez José Manuel , Altomare Corrado , Crespo Alejandro J. C. , Viccione Giacomo
Published: September 2023

The behavior, safety and survivability of offshore moored systems is determined by the environmental conditions, which, along with the wave characteristics, usually include the presence of currents. Their effect modifies the wave pattern and the overall fluid behavior, and may cause inaccuracies in the estimated sea state parameters, which would eventually jeopardize the design of offshore structures. The present work provides the validation of the interaction of a moored floating sphere with the joint action of waves and current by means of the Smoothed Particle Hydrodynamics (SPH) method. An experimental campaign is carried out in a combined wave-current test tank to assess the dynamic behavior of the moored spherical buoy; the experimental data are eventually used to validate a newly developed wave-current flume in the SPH-based solver DualSPHysics. For this purpose, open boundary conditions are implemented to reproduce the fluid flow perceived by the buoy: third order wave-current theoretical flow velocity field and free surface are derived from Stokes wave theory and imposed at the inlet boundary. Thanks to the coupling with MoorDyn+, which solves the mechanics of anchoring systems, DualSPHysics is able to capture the flow-induced moored buoy motion. The results of this preliminary investigation show the feasibility of this approach for simulating moored structure subject to the joint action of waves and current. A useful and practical application for the numerical framework here developed is the high-fidelity simulation of Wave Energy Converters (WECs), for which the action of current could play a significant role in term of loads, motions and power output.
Effect of Polymer Latex and Cement Density in Wellbore Integrity
Authors: Al-Yami Abdullah S. , Al-Qahtani Hussam , Jaber Nizar , Khan Majad , Wagle Vikrant
Published: September 2023

Due to pressure and temperature changes during the life of the well (from drilling to production); globally many Casing-Casing Annular (CCA) leaks could be observed in the annuli between surface and intermediate casings. A new approach to well cementing had to be developed, and advanced cement technologies considered, taking into account both short- and long-term design parameters.

To assess the effect of pressure and temperature cycling on the long-term well integrity, intensive lab work was done to design cement polymer latex formulations at different densities to improve wellbore integrity.

Experimental work in this study contained short term testing and long-term testing. The short-term testing included thickening time and rheology. The long-term testing included curing for 30 days and mechanical properties measurements. Analytical techniques, such as nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared analysis (FTIR), differential scanning calorimeter (DSC), and thermogravimetric analysis (TGA), were used to help with understanding the structures and physical properties of the latex and its interaction with cement matrix.

Conventional cements had values of static Young’s Modulus range between 3 and 3.5 million psi which indicated that the cement was too rigid to resist any type of pressure or temperature cycling. Adding polymer latex improved wellbore integrity by reducing Young’s Modulus. Reducing density resulted in reducing Young’s Modulus values. Combination of low densities and polymer latex should be investigated for future cementing for potential improved wellbore integrity.
Analytical Optimization Approach for Fatigue Analysis of Flexible Pipes Tensile Armors Inside End Fittings
Authors: Miyazaki Marcelo Noboro Ralim , da Silva Vinicius Ribeiro Machado , de Sousa José Renato Mendes , Ellwanger Gilberto Bruno
Published: September 2023

The assembly process makes flexible pipes susceptible to fatigue within the end fitting (EF). Notably, the tensile armors are folded and unfolded during this procedure to install the pipe’s inner sealing ring. This process induces a high level of plasticization at the tensile armors, which impacts their fatigue performance. Hence, initially, this work summarizes an analytical approach to assess the stress-strain loop in the tensile armors due to the assembling of the EF, the factory acceptance test (FAT) of the pipe, and its operation. Relying on this approach and employing optimization techniques, different design scenarios with distinct boundaries and criteria may be considered, leading to an optimized EF. A case study based on a 6” production riser in catenary configuration shows the different impacts of each variable in output (utilization factors, fatigue life, and EF cost).
Critical Review of the Literature on Curing Losses and Long-Term Shale Inhibition
Authors: Al-Yami Abdullah S. , Tahir Muhammad , Khan Majad , Wagle Vikrant
Published: September 2023

Lost circulation is one of the prevalent issues in drilling operations. It holds a negative impact on the oil and gas industry as it is a major source of non-productive time (NPT). Moreover, the process of elimination/control is timely and costly. Lost circulation is the loss of drilling fluids to geological formations rather than circulating back to the surface through the annulus. Lost circulation can be categorized based on the volume of fluid being lost to seepage, moderate, severe, or complete loss, and it occurs in the following types of formations: unconsolidated/highly permeable, induced or naturally-fractured, and vugular formations.

The consequences of lost circulation include, but are not limited to, well control incidents, damage of formation, abysmal zonal isolation, and stuck pipe. Therefore, as the vitality of the well affects the quality of both drilling and production, curing lost circulation is essential.

As the topic of lost circulation holds global significance in the oil and gas industry, huge amount of money is allocated to the research and development of solutions to the issue. Many researchers publish papers addressing different and innovative solutions to the ongoing challenge. Long term shale inhibition challenge will be detailed in the case of total losses. This paper will also show some experimental setup to test long term inhibition in the case of total losses.
Analysis of Offshore Helidecks Turbulence and Hot Gas Plumes – A Systematic Approach
Authors: e Silva Daniel Fonseca de Carvalho , Oliveira Allan Carre de , Chads Carlos Eduardo Holmes , Ferreira Marcos Donato Auler da Silva , Liang Denis Alvin , Dolinsky Mauro Cresta de Barros
Published: September 2023

The air flow surrounding offshore helidecks is subjected to many perturbations and obstacles that may represent additional risks to helicopter operations. There are some standards and recommendations for offshore helidecks that establish some thresholds in terms of turbulence and temperature levels that are acceptable for helideck location during early stages of offshore platforms design (e.g.: CAP437 and NORSOK C-004). Nowadays it is usual to perform such evaluations by using Computational Fluid Dynamics (CFD) techniques. Although the hot gas plume evaluation through simulations is done by the temperature field evaluation directly, the turbulence parameter suggested by the standards is not straightforward to obtain from traditional turbulence modelling approaches adopted in CFD. As already discussed in previous publications, the turbulence criteria can be obtained as a function of the turbulent kinetic energy, which is available in traditional RANS (Reynolds Average Navier Stokes) models. This paper illustrates a systematic approach of turbulence and hot gas plume evaluation around offshore helidecks using CFD. The simulations were performed using real case studies for three different offshore unit concepts, namely a semi-submersible, a spread moored and turret moored FPSO (Floating, Production Storage and Offloading). The results are interpreted in terms of the expected risk levels for each key variables threshold. The temperature evaluation method is based on NORSOK C-004 Temperature Gradient Matrix (TGM) and for turbulence, this paper presents a similar and novel approach, called Turbulence Kinetic Energy Gradient Matrix (KGM) according to the standard deviation of vertical velocity levels cited in CAP-437.
Dynamic Small-Scale Riser Model Experiments: A Physics-Based Algorithm to Recover Lost Measurements From Optical Tracking Systems
Authors: Vernizzi Guilherme J. , Schwenck Franco Maciel Vitor , Defensor Filho Wagner A. , Orsino Renato M. M. , Franzini Guilherme R. , Pesce Celso P.
Published: September 2023

While data acquisition to obtain structural displacement fields is traditionally made with the use of strain gauges and accelerometers, recent focus has been put on the use of optical tracking systems for this purpose. Amongst the advantages of this approach, the lack of interference with the investigated structure and the direct measurement of the displacements can be mentioned. However, in recent experimental efforts in which this approach was taken, two types of issues were observed, namely the presence of spurious measurements or the temporary loss of tracking for some targets. The present work focuses on a novel methodology aiming at pre-processing the raw data acquired using optical tracking systems, based on well known mathematical tools. Using a physics-based algorithm, the effects of spurious measurements is diminished and the missing data is adequately interpolated, thus generating a dataset which is much more adequate for subsequent analyses. Even in the case in which no issues occur, this dataset enhances the available measurements since it provides a continuous function for the displacement field, rather than a scatter of a limited amount of points. Both experimental and fabricated numerical sets of data are used to evaluate the capabilities of the algorithm. It is shown that the methodology herein presented leads to an enhanced dataset in which the limitations of optical tracking systems have remarkably less effect on subsequent analyses.