bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Study on the Automatic Ballast Control of a Floating Dock
Authors: Wen Xueliang , Conde Alejandro Garcia , Zhang Jianan , Ong Muk Chen
Published: September 2023

Ballast control of a floating dock mainly relies on manual control, which requires highly skilled workers to master the ballast water system in several hours. Automatic control of the ballast water system can dramatically reduce the number of workers, improve operational efficiency, and increase safety during the vessel docking process. Motivated by this, this work studies the automatic ballast control of a floating dock and proposes a modified P-controller based on a numerical model for simulating the dynamic process of the floating dock’s operations. The numerical model includes a six-degree-of-freedom (6-DOF) model, a hydrostatic force model, a hydrodynamic force model and a hydraulic model. The hydrostatic force model is developed using the Archimedes law and a strip theory along the longitudinal direction. The hydrodynamic model is made based on the effects of added mass and dynamic damping. The hydraulic model is proposed to deal with the hydraulic calculation of the ballast water system. The present automatic ballast control is designed based on a proportional controller to control the valve opening angles when the pitch or roll angles are larger than corresponding threshold values. During the ballasting and de-ballasting operations without controllers, the roll angles of the dock reach value over 12°, which results from the asymmetric allocation of the ballast tanks. The present proportional controller can help stabilize the dock, i.e., keeping the pitch and roll angles within small allowable ranges of [−0.02°, 0.02°] and [−0.08°, 0.08°], respectively. The present automatic control will be further implemented in the vessel docking cases and can significantly improve the stability of the dock.
Anchoring System of Rigid Riser – Flowline Connection With Torpedo Piles
Authors: Novel Matthieu , Genzani Rachel C. , Solano Rafael F. , Jebali Adel , Scultori Marcio , Camilleri Florent , Valer Carlos , Mustiere Olivier
Published: September 2023

This paper discusses the innovative methodology for the anchoring of the rigid riser-flowline transition (TRF) in the Mero Field located in ultra-deep waters of the Santos Basin, offshore Brazil. The Mero Field is located in the Northwest area of the Libra block. Mero 1 project is composed by rigid MLP flowline systems which operate under high temperature and high inner pressure (HPHT) conditions, two different fluid types (oil and water alternating gas, i.e. WAG), permanent and transient flow regime with several predicted shutdown/start-up cycles during design life, unburied condition, with fully restrained anchoring system in the flowline at the well side and compliant in-line anchoring system (i.e. torpedo piles) at the TRF side interconnecting the SLWR. Suction piles connected to an in-line structure via mooring chain or in-line structure with pin piles are commonly used to anchor the rigid riser-flowline connection to the seabed. Both provide a robust anchoring solution with limited uncertainty with respect to the capability of the system to move under operating condition. The drawback of those solutions is that they often require procurement of heavy subsea structures and availability of large construction vessel for their installation. Despite the significant track record in the oil and gas industry for the use of torpedo piles for anchoring flexible and umbilical risers to avoid large displacement of the lines once installed or to enable design of subsea layout with tight curves, their use for anchoring of rigid riser-flowline connection was a first on Mero 1 project. The paper addresses the benefits and challenges associated with the use of torpedo piles for anchoring of rigid riser-flowline connections looking at every step of the process and in particular the following ones : definition of riser-flowline loading to be transferred to the anchoring system, behavior of anchoring system in operating condition (rendering of slack from embedded mooring chain, soil consolidation, requirement for pre-tensioning, etc.), flowline design limitation and requirement to avoid overloading of subsea equipment associated with the rigid line (pipeline end termination, suction pile, sleepers, etc.) and installation challenges to deliver an effective pipeline system.
Are Rogue Waves Predictable From Field Measurements?
Authors: Breunung Thomas , Balachandran Balakumar
Published: September 2023

Rogue waves, which are defined as waves with a wave height, or alternatively a crest height, exceeding the significant wave height by a certain factor, continue to endanger ships and offshore infrastructure. Hence, reliable rogue wave forecasting is of utmost importance to increase the safety for maritime operations. While the occurrence of rogue waves is widely acknowledged, their emergence remains unpredictable due to the lack of a well-accepted basis for explaining their occurrence. In fact, two popular mechanisms explaining the formation of rogue waves lead to considerably different conclusions about their predictability. On the one hand, a rogue wave could be formed by a superposition of wave trains with unknown phases. With this generation mechanism, rogue wave prediction is not viable. On the other hand, nonlinear focusing leading to the Benjamin-Feir instability gives rise to slowly developing rogue waves. Hence, this rogue wave formation could be detected with significant advance time. Given this background, there is an imperative need to address the basic question: Are rogue waves predictable?

In this article, the authors explore the predictability of rogue waves by constructing and parameterizing neural networks. The networks are trained on available buoy data, which allows not only for an assessment under the most realistic conditions but also for indicating the sufficiency of current ocean measurements for rogue wave prediction.
A Design and Numerical Study on a New Kelp Culture Facility
Authors: Lian Yushun , Shen Shutian , Zheng Jinhai , Boamah Samuel , Yim Solomon C.
Published: September 2023

As the market demand for seaweed products increases rapidly over the last few decades, farming of seaweed has become one of the most economical and environmentally friendly marine operations in aquaculture. Seaweed cultivation areas are primarily concentrated nearshore at present. However, with the expansion of aquaculture facilities, rapid coastal development and industrialization, available coastal area for aquaculture is decreasing sharply. This led to seaweed aquaculture being expanded to deep-water regions. In addition, the seaweed cultivation industry will likely transform from a labor-intensive industry to a technology and mechanization-intensive one. Based on the traditional raft culture facility, this paper develops a new design of a set of kelp culture facility focusing on improving their efficiency and stability. This facility is able to automatically adjust the submergence depth of kelp breeding ropes in different growth periods and dive into the water to withstand wind and waves at extreme sea conditions. The kelp breeding facilities are analyzed using the finite element software ANSYS AQWA. According to numerical analysis results, the dynamic response of aquaculture facilities under different sea conditions is discussed, and the effect of avoiding wind and waves after diving under extreme sea conditions is analyzed. It proves that this facility satisfies the requirements of offshore kelp cultivation, thus providing an essential reference for seaweed cultivation from nearshore to offshore areas.
Study on Cantilever Weighing Technology of Jackup
Authors: Yang Hankun , Wen Yan , Zhou Bo , Li Chunhui , Fan Shida , Yan Yongsi
Published: September 2023

The weight of cantilever beam is an essential part of the lightship weight of a jack-up drilling platform. Its weight and gravity center plays a very important role on the subsequent series of tests, such as inclining test, cantilever beam load test and so on. So how to get the weight and center accurately is a very important step during the construction of a jack-up rig. Based on a JU2000E construction project, this paper introduces the detail process of the whole weighing work of a cantilever beam. It includes the reasonable arrangement of lifting points and preliminary theoretical value of each lifting point, subsequent design of weighing system, the operation and monitor during the weighing process, and at last analyzing the weighing result of each weighing step and comparing the theoretical value and actual weighing result to prove that the arrangement of lifting points, the design of weighing system and site operation are all reasonable. Through the whole tracing of a cantilever beam weighing test, yard has got enough experience for the similar work of the future other jack-up drilling platforms and some other weighing works.
Hydroelastic Analysis of Offshore Floating Photovoltaic Based on Frequency-Domain Model
Authors: Shi Yongkang , Wei Yanji , Chen Zuogang
Published: September 2023

In this study, a frequency domain model for offshore floating photovoltaic (OFPV) hydroelastic response is developed by coupling the potential flow theory and the Euler Bernoulli beam theory. The OFPV was considered as modularized elastical plane in structural analysis while it was simplified as an dense array of rigid bodies in hydrodynamic analysis. The boundary element method open-source code Capytaine is used to solve the scattering and radiation problem. The third-order beam deflection equation is used to describe the continual response between the modules. The matrix method is used to model Euler-Bernoulli beams in structural mechanics, and the beam stiffness matrix is substituted into the structural dynamics equations. The proposed method was validated by comparing the results with the experimental and numerical benchmark. The hydroelastic response of a 300m × 300m OFPV was investigated using the proposed method. The results show that the response of the peripheral modules of OFPV is commonly large while the response of the internal modules may be amplified in specific sea conditions. It was suggested that the additional mitigation measures, such as proper connectors and/or wave dissipation systems, should be introduced into the OFPV design.
Modular Collision Avoidance Using Predictive Safety Filters
Authors: Vaaler Aksel , Robinson Haakon , Tengesdal Trym , Rasheed Adil
Published: September 2023

The number of maritime projects is increasing yearly, including offshore applications, underwater robotics for ocean condition monitoring, and autonomous ship transport. Many of these activities are safety-critical, making it essential to have a robust closed-loop control system that satisfies constraints arising from underlying physical limitations and safety aspects. However, this is often challenging to achieve for real-world systems. For example, autonomous ships at sea have non-linear and uncertain dynamics and are subject to numerous time-varying environmental disturbances such as waves, currents, and wind. There is growing interest in using machine learning-based approaches to adapt these systems to more complex scenarios. However, there is currently no standard framework to guarantee the safety and stability of such systems. Predictive safety filters have emerged recently as a valuable method for ensuring constraint satisfaction, even when unsafe control inputs are used. The safety filter approach leads to a modular separation of the problem, allowing the usage of arbitrary control policies in a task-agnostic way. In this work, a predictive safety filter is developed to ensure anti-grounding and ship collision avoidance for a small prototype ferry. The filter takes in a nominal input sequence from a potentially unsafe controller and solves an optimization problem to compute a minimal perturbation of the nominal control inputs, which adheres to physical and safety-related constraints. The system is validated by simulations for several realistic scenarios with map data from Trondheim, Norway. It is demonstrated that the predictive safety filter can avoid collisions with static and dynamic obstacles. The predictive safety filter approach is flexible and can be used to improve the robustness of various offshore applications, e.g. wind turbine stabilization, autonomous vessels, and marine robotics.
Evaluation of Wear and Damage on Large-Diameter Disc Cutters
Authors: Tytler Oluwafemi , Li Zijian , George Judith , Butt Stephen
Published: September 2023

The disc cutter is commonly used on cutter heads for drilling engineering, including tunnel boring, raise drilling, large diameter drilling, etc. Continuous use of the disc cutters over an extended penetrating time during drilling will lead to the disc cutter’s wear and damage, which then leads to reduced drilling performance, lost time, and ultimately higher economic cost. Therefore, it is significant to evaluate the development of the wear and damage of disc cutters in the drilling process and how they influence the overall drilling operation, thereby improving drilling performance prediction and cutter life assessments. In this study, the disc cutter wear and damage development were studied based on several ongoing field trials and research, and a quantitative method of measuring the wear and damaged of disc cutters was developed and has been used over the course of the research project.
Investigation of the Microstructure of Bismuth Alloy and its Interaction With Cement and Steel Casing
Authors: Manataki Andriani , Kontis Paraskevas , Sangesland Sigbjørn
Published: September 2023

Well-plugging and abandonment (P&A) of oil and gas wells involve the placement of barrier plugs at critical intervals in order to prevent leak paths between the reservoir and the surface. As per the Oil and Gas UK Well decommissioning Guidelines a barrier material, among all the prerequisites, should also provide an interface seal or bond, preventing flow around the barrier plug at the interfaces with adjacent casing steel or formation rock. So far, the most well-known barrier material is cement. It is well-qualified, but since it has also some limitations, other materials, such as bismuth-based alloys, have been investigated as an alternative to cement. This study focuses on the use of the eutectic BiSn alloy for well plugging, with 58% bismuth (Bi) and 42% tin (Sn). Like all bismuth-based alloys, this alloy expands on solidification, which is considered an important property for improving its sealing capability in a well. In addition, the microstructure resulting from the interactions between the BiSn alloy, cement, and steel casing, will affect the sealing performance. For this purpose, lab tests have been carried out using a small-scale test set-up. By scanning electron microscopy, various microstructures, in the BiSn alloy were observed and correlated with the interaction of the alloy with the steel casing and the presence of cement.
Innovative Crash Barrier Concepts to Prevent Ship Collisions With Wind Turbines
Authors: Otto William , Koldenhof Yvonne , Buchner Bas
Published: September 2023

The rapid development of offshore wind farms coincides with a growing amount of ship movements. This combination puts pressure on maritime safety, especially in the North Sea where space is limited. This risk was demonstrated at January 31st 2022, when bulk carrier Julietta D got adrift in a wind farm under construction. MARIN estimated that the annual probability of a collision between a ship and a wind turbine will be 1.5–2.5/year in 2030.

There are several mitigations possible to prevent ship-to-turbine collisions. As addition to the existing measures, MARIN investigated another innovative solution, a ‘crash barrier at sea’. A variety of barriers has been conceptualized by a team of industry experts. Out of this variety, three concepts were distilled for further analysis: A) a floating surface line, B) a mid-water buoy line and C) a pile supported net.

To test the three concepts, explorative scale model tests have been performed in MARIN’s Offshore Basin. As a reference case, a free drifting vessel similar to the Julietta D, in scaled storm conditions similar to January 31st 2022, was modelled. In general we can conclude based on these very initial experiments that collisions between drifting ships and offshore windturbines can in principle be prevented with these types of barriers, but also that they need further development, validation and evaluation with all partners involved.
Lumped-Mass Model to Represent the Installation Process of Subsea Equipment
Authors: Salvador Lopes Filipe , Fernandes Antonio Carlos , Sena Sales Junior Joel , Martins de Andrade Emerson , Machado João Paulo
Published: September 2023

The installation of subsea equipment is a complex process and due to that different installation methods were developed throughout the years, as the vertical installation method, which is this work’s focus. One of the main concerns when vertically lowering an equipment regards the tension on the installation cable, which might spike due to the high amplitudes of the equipment’s motions. If the tension on the cable exceeds its minimum break load the equipment will be lost. Therefore, this process must be properly simulated, to determine safe operation windows for installation. A numerical model to simulate this installation process was developed, using a lumped-mass model to represent the cable, and the six degrees of freedom of the equipment were considered during the simulations. Special attention was given to the possibility of snap loads occurrence, and the fourth-order Runge-Kutta method was used to solve the equations of motions of both the equipment and the cable, to provide the cable’s tension time series. The results obtained by the numerical model were compared to benchmark data and good adherence was found. It was observed that the cases in which the snap loads occur are indeed the ones in which the highest tension values happen, which indicates that these are the critical conditions for the installation operation.
What a Wave Buoy Actually Measures in 3D: Analysis of a Mild Sea State
Authors: Ding Yue , Taylor Paul H. , Zhao Wenhua , Dory Jean-Noel
Published: September 2023

Measurements of surface waves from oceanographic buoys have been regarded as the ‘ground truth’ for validation of sea-state prediction models, providing the basis for input to the design of offshore structures. The engineering practice is to produce wave statistics of vertical surface displacements over periods of years. However, a wave buoy can provide simultaneous time histories of its motion, one vertically and other two horizontally, giving the complete vector displacement field in time. We investigate the measured time histories of a wave buoy in three orthogonal directions, and explore the relationship between them, for a relatively benign, so typical, sea state. We adopt a NewWave-type analysis to investigate the average shape of the large events across the measured time histories. In combination with a conditioning analysis, we give a reciprocity relationship between the vertical displacement of the wave buoy and those in the horizontal plane. The relationship is of value, as it allows for the prediction of wave kinematics in the horizontal plane based on the vertical measurement only. We observe significant second-order components in the measured data in the horizontal directions and smaller contributions vertically. This data-driven analysis paves the way for wave-by-wave prediction and the active control of wave energy converters and floating wind turbines in engineering practice.
Scale Effects and Variability in Wave-in-Deck Type of Impact Loading, More Insights Into the Results of the BreaKin JIP
Authors: Scharnke Jule , Helder Joop
Published: September 2023

To quantify the loading due to breaking waves, model tests are currently the option of choice. However, it is suspected that scale effects lead to an overestimation of the prototype loading. As such, a typical question in impact load assessment is how conservative load measurements are. To understand how realistic model testing is in this respect, it is necessary to quantify scale effects in the measured loading due to breaking waves as well as to investigate to which extent entrapped air in the wave and during the wave impact is involved. To do so, the BreaKin Joint Industry Project was started in 2016. The objective of the BreaKin JIP was to get more insight into scale effects involved in wave-in-deck model tests and to take first steps towards linking wave kinematics with measured impact loads. During this JIP wave-in-deck model tests were carried out in MARIN’s Depressurized Wave Basin (DWB) at two scales (25 and 50) in atmospheric and depressurized condition. In previous work, a summary overview of these model test results was presented [1]. The current paper provides more in-depth insights into possible sources of scale effects involved in wave-in-deck type of loading, based on further analysis of the existing model test data. It includes a detailed review of a.o. local loads in correlation to the variability of measured (global) impact loads between repeat measurements.
Data Extraction Algorithm for Power and Speed Performance Analysis of Operating Vessel Based on Sliding Time Window
Authors: Wen Yiyan , Ma Ning , Shi Qiqi , Zhang Yanfei , Zhang Ziwen
Published: September 2023

Engine power and voyage speed performance analysis of operating vessel has strict requirements on the size and quality of operational data sets. A sliding time window and information entropy based algorithm for stable navigation interval extraction of operating vessels is proposed. Chebyshev’s inequality is introduced to clean the noisy data from the operating ship data and identify multiple feature parameters that are highly correlated with the engine power. By introducing a sliding time window, the period T of the sliding time window is determined using the trend of the autocorrelation coefficient between the features, and information entropy is introduced to analyse the multiple features to determine the stable operating interval of the main engine of the operating vessel. The results show this algorithm has strong adaptability and quality improvement effect for the operational big data filtering and extracting which is related to engine power and voyage speed analysis.
Comprehensive Evaluation of Surface Ship Performance Based on Deep Reinforcement Learning
Authors: Ji Shengchen , Wang Hao , Luo Liang , Hao Zhailiu , Li Shengzhong
Published: September 2023

In order to evaluate the performance of surface ships accurately, this paper presents a comprehensive evaluation method based on deep reinforcement learning. The evaluation index system involves ship hydrodynamics, structural safety and stealth. And the initial index weights of each level are calculated by the hierarchical analysis method. Considering the difficulty of weight calculation caused by too many evaluation indicators, a weight correction model based on deep reinforcement learning is proposed. The model can quickly revise the index weight according to the subjective opinions of experts. For verifying the effectiveness, a comprehensive evaluation test of surface performance is conducted based on the published data of Type 5 surface ships. The findings demonstrate that deep reinforcement learning can produce intelligent index weight and assessment result corrections based on the knowledge of numerous experts.
When Do JONSWAP Spectra Lead to Soliton Gases in Deep Water Conditions?
Authors: Lee Yu-Chen , Brühl Markus , Wahls Sander
Published: September 2023

When a large number of solitons dominates the dynamics of a system, scientists describe this collective behaviour of solitons as a soliton gas. Soliton gases are currently the subject of intense practical and theoretical investigations. The existence of soliton gases has been confirmed in experiments, but is not clear what kind of sea states might lead to soliton gases. Therefore, in order to determine the wave parameters for sea states that lead to soliton gases, large numbers of surface wave elevations are generated by the well-known JOSNWAP model in this paper. Here, we only discuss soliton gases in deep water governed by the nonlinear Schrödinger (NLS) equation. The nonlinear Fourier transform (NFT) with vanishing boundary conditions is applied to the simulated ocean surface waves. The resulting nonlinear Fourier spectrum is used to calculate the energy of radiation waves and solitons. We investigate which JONSWAP parameters result in sea states that can be characterized as soliton gases, and find that a large Phillip’s parameter α, a large peak enhancement parameter γ and a short peak period Tp are important factors for soliton gas conditions. The results allow researchers to estimate how likely soliton gases are in deep waters. Furthermore, we find that the appearance of rogue waves is slightly increased in highly nonlinear sea states with soliton gas-like conditions.
Nonlinear Aero-Mooring Effects on Floating Offshore Wind Turbines Under Random Wind and Waves: Environmental Direction Effects
Authors: da Silva Leandro Souza Pinheiro , Y. Sergiienko Nataliia , S. Cazzolato Benjamin , Kiu Kwong , T. Gonçalves Rodolfo , Ding Boyin
Published: September 2023

Floating offshore wind turbines (FOWTs) have been extensively investigated to harvest the vast offshore wind potential at transitional to deepwater locations. Among the main FOWT components, mooring systems play an important role in the platform dynamics, being the primary source of restoring force in the surge and sway directions. For such degrees, the platform motion can be highly affected by turbulent wind loads due to the platform’s low natural frequencies. Catenary mooring systems are generally applied to FOWTs, which are characterised by nonlinear loads (asymmetrical). In such a system, when the mean aerodynamic thrust force acts on the platform, it leads to an offset position that modifies the mooring restoring force, changing the platform’s natural frequency. In this context, this work investigates the aero-mooring nonlinear effects on the platform dynamics under environmental conditions coming from different directions. The OC4 semi-submersible platform supporting the NREL 5-MW baseline offshore wind turbine with three catenary lines is chosen as a base case. The FOWT is subject to random loads from the wave and wind (temporal and spatial effects). Since efficient tools are favourable during the initial stages of development and in assessing an extensive range of environmental conditions, the numerical model is built using frequency domain modelling and statistical linearisation to estimate the nonlinear effects. The results show that the nonlinear mooring loads affect the natural frequency, making the platform more susceptible to stochastic wind loads when the environmental direction comes with an angle of 60° with respect to the platform.
Design of Mooring System for a 15MW Semi-Submersible, TaidaFloat, in Taiwan Strait
Authors: Chen Chi-Ang , Chen Kai-Hung , Igarashi Yuki , Chen Donghui , Ma Kai-Tung , Lai Zhao-Yu
Published: September 2023

Floating offshore wind turbine (FOWT) is one of the trending topics in the offshore industry. Taiwanese government agency, Bureau of Energy, recently announced a 100 MW floating offshore wind turbine demonstration project, which is planned to be installed in Taiwan Strait to have a jump start in the readiness of floating wind technologies. Compared with bottom-fixed offshore wind turbines, semi-submersible FOWT has many advantages, among different floater types, in economic efficiency as offshore wind farms go to deeper water. This paper summarizes the design of a mooring system and the anchor type selection for a concept floating system, TaidaFloat. TaidaFloat is a floating platform designed to support a 15 MW wind turbine in a water depth of around 70 meters. The mooring design follows the rules and guidelines of American Bureau of Shipping. 3 × 2 and 3 × 3 mooring patterns are investigated for feasibility of withstanding the winds, waves, and currents in Taiwan Strait. According to the rules, the mooring system must sustain an environmental load of a 50-year return period. The priority of the design is to minimize the cost and the footprint of the mooring system. OrcaFlex and ANSYS Discovery are used for the analyses. The results show that a 3 × 3 mooring pattern with an anchor distance (radius) of 10 times water depth is required to meet the design targets under extreme environmental conditions. Anchors of around 23tons are needed to withstand the mooring loads. Overall, in the current design, the mooring chain size and anchor weight turned out to be relatively large as compared to other designs. Reducing the cost of the mooring and anchor systems remains to be a challenge in future work.
Temporal Discretization Investigation of the Unsteady Loading on an Infinitely Long Cylinder in High Reynolds Numbers Using DES
Authors: de Oliveira Marielle , da Silva Leandro S. P. , Saltara Fabio , Carmo Bruno S. , Gonçalves Rodolfo T.
Published: September 2023

The flow around circular cylinders has been extensively investigated over the past decades, both numerically and experimentally, due to its importance in offshore applications. However, the phenomenon of vortex shedding remains not completely understood at supercritical and postcritical regimes due to difficulties in representing the nature of separated flows past bluff bodies at such high Reynolds numbers. This work thus presents a numerical investigation of the flow field and its forces on a circular cylinder at supercritical and postcritical Reynolds regimes using Computational Fluid Dynamics (CFD), more specifically the Finite Volume Method (FVM) implemented in the Open-FOAM software. The flow past a fixed circular cylinder of aspect ratio equal to 2 and periodic boundary conditions at its ends is assessed for Re = 1 × 106, 3.6 × 106, and 1 × 107. We employed the hybrid detached eddy simulation (DES) along with Menter’s k-ω SST model as a turbulence closure model, and analyzed the loads acting on the cylinder and other flow features, such as Strouhal frequency, at each regime. A temporal discretization analysis was carried out for the Reynolds regime of 107, whereby three different Courant-Friedrichs-Lewy (CFL) numbers were tested, namely CFL equal to 0.25, 0.5, and 1. The capability of each CFD simulation in capturing the physics of the system is assessed by comparing it with results found in the literature for similar cases, in terms of lift and drag coefficients, and Strouhal frequency. The numerical investigations presented satisfactory results for all cases; however, a considerable increase in the computational demand was noticed for higher Reynolds numbers and lower CFL numbers, CFL = 0.25 and 0.5.
Integrated Optimization of Hybrid Steam-Solvent Injection in Post-CHOPS Reservoirs Under Uncertainty
Authors: Hou Senhan , Yang Shikai , Jiang Liwu , Yang Daoyong
Published: September 2023

In this paper, an integrated algorithm is proposed to optimize the hybrid steam-solvent injection-production schemes for post-CHOPS reservoirs under uncertainty. First of all, the newly developed pressure-gradient-based (PGB) sand failure criterion is employed to generate dendritic (or fractal-like) and regional wormhole networks, based on which the net present value (NPV) is defined and used as the objective function. A hybrid optimization technique based on the genetic algorithm (GA) is then integrated with the orthogonal array (OA) and Tabu search to maximize the objective function by rationalizing the injection and production parameters and simultaneously retarding the displacement front to extend the reservoir life under uncertainty. In a given CHOPS well, not only can the proposed method be used to determine the overall morphology of the wormhole network, including intensity and coverage, but also design, evaluate, and optimize performance of any potential EOR processes in a post-CHOPS reservoir within a unified, efficient, and accurate framework.
Numerical Investigation of Air-Blast Performance of Cross-Filled Honeycomb Sandwich Panel
Authors: Patel Murlidhar , Patel Shivdayal , Ahmad Suhail , Soares Carlos Guedes
Published: September 2023

Today’s biggest terrorist attack is the blast. The public and property are suffering significant harm as a result of the explosion. However, the modern period is looking for a structure that is blast-proof to safeguard people and pricey properties from explosions. Sandwich panels have an excellent capacity to absorb energy under blast as well as impact loads. As a result, a unique blast-proof sandwich panel was created in this study by using a cross-filled reinforced square honeycomb core. The investigation of blast mitigation performance through experiment is very dangerous, costly, and environmentally polluting. However, to overcome these issues, by using ABAQUS/Explicit, the blast mitigation performance of the modelled honeycomb sandwich panels was examined for a constant stand-off distance (SoD) of 100 mm at 1 kg to 3 kg TNT air-blast loadings. This study was carried out after the mesh convergence and validation studies. The new sandwich panel design’s blast resistance was examined by measuring the face deflection and energy absorption capabilities under air-blast loadings. A sandwich panel made of a reinforced square honeycomb core significantly increases blast resistance by reducing face deflection and increasing energy absorption contribution by the core. Compared to the sandwich panel with a square honeycomb core and a cross honeycomb core, the novel designed sandwich panel exhibits greater core energy absorption contribution, a smaller front face, and smaller rear face deflection at all applied air-blast pressures. Therefore, the sandwich made with a cross-filled square honeycomb core has the greatest blast-proof properties. The newly created sandwich panel may be used for several armoured vehicle components to protect soldiers.
A New Method for the Design and Coupled Analysis of Floating Offshore Wind Turbines
Authors: Veen Daniel , Pahos Spiro J. , Meng Shawn , Dillenburg Simon
Published: September 2023

Global power generation from floating offshore wind turbines is expected to grow from 132 MW in 2022 to 289 GW by 2035. During the design phase these floating systems will require advanced numerical analysis tools to ensure strucutural integrity and reliability.

A new method for the hydrodynamic analysis of these structures is presented. The long standing offshore operations simulation software MOSES has been enhanced with the addition of the AeroDyn aeroelastic wind turbine solver from OpenFAST. This coupled analysis tool is designed to compute the motions and loads on the floating system. An added benefit of using MOSES is that these loads can be readily mapped on to a structural model for assessing code compliance.

In this paper the MOSES-AeroDyn solver has been validated against published numerical and model test data of the OC3-Hywind system in regular waves. The coupled MOSES-AeroDyn results were found to be in good agreement with both the experimental and numerical data.
Numerical Study on the Deceleration Effect of Impact Velocity of Tsunami Drifting Objects in Front of Structures
Authors: Takekawa Mebae , Aida Yasuhiro , Nakazawa Hibiki , Sasaki Ami , Ikoma Tomoki , Masuda Koichi
Published: September 2023

Several formulas have already been proposed to predict the impact force of flotsam caused by tsunamis. All of these equations require the impact velocity of the flotsam to calculate the impact force, and many studies have been conducted on the drifting velocity of the flotsam. Although CFD calculation methods have been used for such as problems, detail of behaviors of the flotsam colliding with a structure is still unclear. However, it has been known that the drifting velocity in front of the structure decreases very much. In order to improve accuracy of the impact force, the deceleration and the behaviors should be clarified.

A purpose of this study is to investigate effects of the deceleration of a drifting object as flotsam in front of the structure. In this study, the MPS method was used to predict behaviors of the object in tsunamis. Then, the study estimated run-up height in front of the wall of the structure. in addition, the effects of the ratio between length of the drifting object and width of the wall and tsunami incidence angles were varied.

Numerical simulation results showed that the velocity before collision decreased when the tsunami incidence angle is 0 degrees,, the velocity decreased very much rather than 0 degrees cases when the width of the structure is wider than it of the object, and when the tsunami incidence angle is 45 degrees.
Time-Series Forecasting for Health Monitoring of Marine and Offshore Renewable Energy Systems
Authors: Abaei Mohammad Mahdi , BahooToroody Ahmad , Arzaghi Ehsan , Abbassi Rouzbeh , Inkinen Tommi , Garaniya Vikram
Published: September 2023

Marine and Offshore renewable structures are widely being developed across the globe, and specifically in Australia, under controlled conditions with little focus on having advanced health monitoring systems, optimization of the structures design and operation to undertake complex operations. Considering a data-driven approach to health management is an essential part of the future offshore renewable energy industries. It allows the detection of critical faults and assists in estimating the remaining useful lifetime (RUL) facilitating more reliable offshore renewable structures. Despite the advantage of machine learning techniques in asset health condition monitoring, few studies have considered the integration of such prognostics into maintenance planning for remotely operated offshore facilities. This paper proposes a model to help the marine and offshore industry in real-time maintenance planning. The model will consider the imperfect RUL prognostics incorporating higher degrees of uncertainty involved with remotely operating systems in offshore environments. A Bayesian Meta-Model is developed for time series change point (CP) detection of multiple anomalies in a random process. The proposed methodology will be useful in incipient failure detection and maintenance planning of complex systems operating in harsh and highly random marine environments.
Computational Fluid Dynamic Modelling of Vortex-Induced Motion of Wind Turbine Monopile Foundation During Installation
Authors: Liu Shengnan , Moen Petter , Fiore Fabrizio
Published: September 2023

The vortex-induced-motion (VIM) of a hollow monopile is investigated using a three-dimensional two-phase Computational Fluid Dynamic (CFD) model in ANSYS CFX. The turbulence effects are modelled using the k-omega SST turbulence model. Both air and water phases are included in the numerical model to consider the variation of the buoyancy due to the rigid body motion. Dynamic mesh techniques with six-degree-of-freedom (DOF) rigid body are used to capture the motion of the monopile. The mesh and time step convergence studies are conducted first, and the converged numerical set-up is used for the other cases. The numerical model is validated against the model test measurements for VIM of a scaled monopile foundation by Seaway7 to show the applicability of the present numerical model for the VIM prediction in subcritical flow regions. The characteristics of the inline and cross-flow motions, hydrodynamic coefficients and flow fields are discussed.
Frequency Domain Dynamic Response Analysis of Three Parallel Ships in a Twin Marine Lifter System
Authors: Zhang Huan , Teng Yanjun , Fan Shida , Wang Yuhan , Wang Chao , Yin Yan
Published: September 2023

Many aging large offshore platforms are facing the problem of decommissioning and dismantling. In this paper, a method of removing the upper module of the platform by using a twin marine lifter system (TML) is proposed. In order to study the reliability of this method, added mass, damping, wave force and RAO of the three-ship system are analyzed, and the influence of three-ship interaction and water depth on the hydrodynamic parameters of the three-ship system are investigated. The hydrodynamic analysis is carried out under different environmental conditions, and the variation characteristics of the hydrodynamic parameters of the ship in the three-ship system are obtained. The results show that when three ships are alongside, the interaction of the three ships will have a significant effect on the hydrodynamic parameters, and the interaction of the three-ship system on the hydrodynamic parameters is mainly in the wave frequency range; The system is sensitive to changes in sea state conditions, and the motion response is maximum when the wave angle is 90° and minimum at 0°, but there is still some lateral motion. In practical operation, it is necessary to avoid the wave frequency and the direction of environmental load when the motion response is large, and consider the relevant effects in mooring and dynamic positioning.
A Numerical Assessment of Mooring System Modelling Uncertainties in Hydrodynamic Model Testing of Floating Wind Turbines
Authors: Berthelsen Petter Andreas , Thys Maxime , Bachynski-Polić Erin
Published: September 2023

This paper presents a general uncertainty assessment in hydrodynamic testing of a floating wind turbine. A general uncertainty analysis is often carried out when the goal is to assess the sensitivity of the results to uncertainties in the input variables, regardless of whether the uncertainty is of systematic or random nature. The analyses are based on the 12MW INO WINDMOOR semisubmersible floating wind turbine. The assessment is carried out as a numerical study of the WINDMOOR hydrodynamic experiment [1]. A global simulation model of the experimental setup is established in the simulation framework SIMA. The propagation of uncertainty is assessed using two different approaches: The classical Taylor Series Method (TSM) and the Monte Carlo Method (MCM). Specifically, the uncertainties in the mooring system and their effects on the mooring line tension and platform responses are investigated. The assessment is performed for a range of standard uncertainties in the input variables, and the results from the two methods of assessing the uncertainty are compared.
The General Nonlinear Stiffness Matrix of Taut-Leg Platforms, TLPs and Suspension Systems of Cable-Connected Floater-Keel Platforms
Authors: Esber Ghaith , Kosleck Sascha
Published: September 2023

The static and dynamic behavior of taut-leg and tension leg platforms (TLPs) is highly characterized by the stiffness properties of their mooring systems. That also applies to the innovative offshore floating wind turbine platforms that are composed of a floater connected to a keel only via suspension cables. Several works have tried to derive the nonlinear stiffness matrix of such systems. Yet, the results are only partially similar. In this study, a general approach is developed for deriving the nonlinear tangent stiffness matrix of a floating platform moored with a single taut line. The stiffness matrix is derived using the virtual work principle as a function of the platform’s general displacement. The derived matrix is analytically verified. Furthermore, the stiffness matrix of a rectangular taut-leg platform and a rectangular TLP is constructed and their initial forms are computed and compared to previous works. In addition, the innovative floating platform concept CBTS (cable-based truss spar) is introduced and the previously presented methodology is adopted to derive the general nonlinear stiffness matrix of its suspension system. The floater initial pitch stiffness of the CBTS platform is further investigated at different initial positions of the platform.
Non-Linear Hydrodynamic Forces on Fixed Axi-Symmetric Bodies in Incident Waves
Authors: Tan Bryan , Orszaghova Jana , Kurniawan Adi , Wolgamot Hugh , Hals Todalshaug Jørgen
Published: September 2023

Hydrodynamic forces induced by surface gravity waves on a wave energy converter directly influence its motion and power capture. Characterisation of these forces is therefore critical to optimising the hydrodynamic design of these devices. This study experimentally investigates linear and higher harmonic hydro-dynamic forces on a fixed sphere at different immersion levels. Diffraction tests are performed in a wave flume where an aluminium sphere is instrumented with a 3-axis load cell to measure the induced horizontal and vertical forces experienced while subjected to incident focused wave groups with different focus amplitudes. The force harmonics are separated using two-phase harmonic separation and subsequently analysed. The measured first harmonic excitation force is found to be consistent with numerical results across all immersion levels but exhibits weak amplitude dependency. The second and third harmonic excitation forces appear to be consistent with the expected quadratic and cubic dependence on the incident wave amplitude. The second-order super-harmonic surge force is found to be the same order of magnitude as the linear force for the largest amplitude case considered. Dependence of the first, second, and third harmonic excitation forces on the immersion level is also investigated, motivated by the small-body approximation for linear forces.
A Fast Algorithm for the Prediction of Distance at Closest Point of Approach in the Maneuvering of Two Ships
Authors: Xu Chen , Jiang Fan , Xu Chaozuo , Zhou Xueqian , Ren Huilong
Published: September 2023

The situation of two ships maneuvering in the vicinity is not so rare, and the significant hydrodynamic interaction effect always poses a threat to navigation safety in these conditions. The assessment of distance at closest point of approach (DCPA) is necessary for ship collision avoidance decision-making. In this study, an efficient ship maneuvering model for close-distance maneuvering is developed to predict DCPA rapidly, where the hydrodynamic interaction between ships is accounted for. The MMG model is used to predict ship motion, and the hydrodynamic interaction effect is estimated in real-time by a code based on the potential flow theory where the variation of free surface is neglected. The ship maneuvering model is validated by the comparison between simulation and experiment in turning and zig-zag maneuvering, furthermore, the validated maneuvering model is used to predict the trajectory under the ship hydrodynamic effect. The characteristic of ship maneuvering under the ship hydrodynamic interaction between two ships is described and illustrated, and the influence of the velocity and lateral distance on the ship trajectory is revealed. A sensitivity analysis of the maneuvering model is performed to determine whether the hydrodynamic interaction effect is necessary to be evaluated exactly for an accurate predicted trajectory and DCPA. The DCPA in different situations are calculated which represents the ship collision risk.
Some Background for the 2023 Revision of the Recommended Practice DNV-RP-C203 Fatigue Design of Offshore Steel Structures
Authors: Lotsberg Inge , Fjeldstad Arne
Published: September 2023

The recommended practice DNV-RP-C203 Fatigue Design of Offshore Steel Structures has been regularly revised since it was first published in 1998. The reasons for these revisions are new data and new learnings from design and in-service experience from installed structures. The standard is also being used for new types of details and structures, and this requires new information to the users of the document. New literature is being published and other standards related to fatigue design is being revised; therefore, a regular revision of this document is needed.

The standard is being used for fatigue design of different structures such as jackets, risers, pipelines, semisubmersibles, spars, floating production vessels, fixed and floating structures for support of wind turbine structures, different types of connectors, etc. This implies that the content needs to be applicable for many different details where the efficiency and reliability of the methods used are being challenged by the industry. During the last year the recommended practice has been through a critical review where the content has been updated where new information has become available.