bluuebunny/crossref_metadata_2025 huggingface dataset:
Petro-AIMS: Implementation of Muhlbauer and El Reedy Method for Integrated Subsea Pipeline and Offshore Platform Integrity Management System
Authors: Pravi Maulidiyah , Putra Bakti Farid , Surjadi Frederick Gavin
Published: August 2024

This study investigates the implementation of combining two risk assessment methods that was developed for two distinct types of assets: the Muhlbauer and El Reedy techniques. The Muhlbauer method was developed for pipeline assets, while the El Reedy method was developed for offshore jacket platform assets. Even though they were developed for different type of assets, both Muhlbauer and El Reedy method uses the same straight-forward semi-quantitative risk assessment framework. The implementation of combining the two method is done within a web-based asset integrity management system: Petro-AIMS environment. To demonstrate a real-world case application of the proposed method, the data from four offshore platforms that are connected to ∼70 km offshore subsea pipeline is investigated. By implementing the same Likelihood of Failure (LoF) and Consequence of Failure (CoF) assessment framework for two different asset type, it is shown that Petro-AIMS is projected to be a practical and effective tool to perform asset integrity management function.
Optimization for Buoyancy Modules Attachment on Riser System for the Production of Polymetallic Nodules
Authors: Yamamoto Marcio , Yamamoto Joji , Masanobu Sotaro
Published: August 2024

The exploitation of polymetallic nodules will require the use of riser systems longer than 4,000 m. The main issue of such riser systems is that the effective tension increases linearly with length and overcomes the riser material’s yield strength at its top portion. Thus, buoys must be attached along the riser to reduce this effective tension. In this article, we apply a classic Genetic Algorithm to optimize the number and position of these buoys. The algorithm was set to minimize the failure criterion defined in a standard of riser pipes. This failure criterion considers the effective tension and bending moment. The evaluation function was calculated using only the static result of the riser simulation. However, the Genetic Algorithm minimized the failure criterion by reducing the riser’s effective tension with attached buoys. The dynamic simulation results show that this reduced effective tension raised other issues, such as large amplitudes of the effective tension and bending moment; even axial compression was observed. A large effective tension variation may result in the Mathieu Instability. The large bending moment variation may result in cumulative fatigue damage. At the same time, axial compression may cause the riser to buckle.
A Study on Route and Fuel Oil Consumption of Ships Considering Change of Weather Derived From Climate Change
Authors: Sogihara Naoto , Tsujimoto Masaru
Published: August 2024

Climate change brings significant impacts on various industrial sectors. In shipping sector, it is expected in future that weather condition such as winds and waves at sea will be different from current one. This makes significant influence on ships in service. As a ship navigates in winds and waves, the fuel oil consumption changes by the encounter weather condition. Accordingly, even though the ship route is not changed, the amount of the fuel oil consumption in future is different from the current one due to the effect of the climate change. Besides, an oceangoing ship navigates on an optimized route based on the weather routing system, generally. Therefore, in future the optimized route will be changed, which is affected on the climate change.

At Intergovernmental Panel on Climate Change (IPCC), Representative Concentration Pathways (RCP) scenarios are indicated in the fifth assessment report. In the report four concentration scenarios of greenhouse gases (GHG) are used for the prediction of the climate change. There are some investigations on weather condition in future based on RCP scenarios.

This paper addresses the climate change impact on the fuel oil consumption of ships in service and focuses on the fuel oil consumption of an oceangoing container ship in North Pacific Ocean. The fuel oil consumption in the great circle route and the optimized route are calculated under the present weather condition and future one based on RCP2.6 and RCP 8.5. Finally, the climate change impact on the fuel oil consumption is discussed.
One-Way Fluid-Structure Interaction of Submerged Floating Tunnel Under Current Action
Authors: Pathak Keshav , Saha Nilanjan
Published: August 2024

The submerged floating tunnel (SFT) is a long tunnel that remains suspended below the water surface at a considerable depth of around 100–150 m and connects to land masses separated by ‘deep’ and vast water bodies. The present study aims to characterize the flow dynamics around an excessive buoyant type SFT with a circular cross-section. In this paper, one-way fluid-structure interaction analysis is carried out to analyze the dynamic behavior of SFT under current action. Computational Fluid Dynamics (CFD) is implemented to perform a 2D numerical simulation of flow around the SFT cross-section. The k-ω SST turbulence model is implemented to capture the turbulence flow around the structure. The hydrodynamic load from the CFD solver is then sequentially transferred as a uniformly distributed transient load to a structural solver to study the dynamic behavior of the SFT tube segment. In structural solver, only a part of the structure separated by mooring lines at two ends (or SFT tube segment) is considered. Here, the structure is modelled as a Euler-Bernoulli’s beam, discretized as line body elements, and supported by linear vertical springs equivalent to mooring lines at two ends. The structural response of the SFT tube segment and the flow pattern around the structure are discussed and validated from the literature.
Self-Righting Characteristic of Autonomous Surface Vehicle Under Intact and Damage Conditions
Authors: Yanyun Yu , Kai Li , Yunlong Wang
Published: August 2024

In this paper, the concept of self-righting characteristic is introduced into stability analysis of Autonomous Surface Vehicles (ASVs) in order to improve their safety in rough sea. Firstly, the requirements of self-righting characteristic are discussed with the extended GZ curve that covers heeling angle range from 0 to 180 degree, based on the boundary-representation (B-Rep) solid floating body. Then an iteration process is proposed to calculate the righting lever at any heeling angle. With the extended GZ curve for different height of Center of Gravity (CG), the stability surface is created, and applied to compute the curve of extreme height of CG, which is the height limit of CG for ASVs if self-righting characteristic is required. Finally, the damage stability of ASVs is discussed, including how to make ASVs unsinkable, how to treat damage tank/room, how to compute floating state and GZ curve with B-Rep model in damage conditions, and how to analysis the self-righting performances of ASVs with the extended GZ curve etc. An ASV with self-righting hull form is taken as example to illustrate the principles and methods proposed in this study.
Full-Scale Measurements of Offshore Monopile Foundations and Numerical Benchmark
Authors: Winkler Kristof , Sastre Jurado Carlos , Stuyts Bruno , Weijtjens Wout , Devriendt Christof
Published: August 2024

In offshore wind, the modelled structural dynamics used in design do not fully describe the reality of build structures. For monopile supported turbines, previous work and other publications show an underestimation of eigenfrequencies. As fatigue and lifetime of a foundation is strongly dependent on using these eigenfrequencies, better models that more accurately predict reality are needed. This paper will present eigenfrequency measurements taken at two monopile foundation locations with a sandy topsoil layer and one with a clay topsoil layer within the same windfarm in the Belgian North Sea. The three datasets span a timeframe of around eight months, during which a rock armor scour protection was installed and the structures consisted of monopile foundations including a transition piece. Analyzing these measured eigenfrequencies we can see correlations with variable sea state, specifically with tidal level and wave height and period. Also the moment of scour protection installation is detectable by a consistent increase in eigenfrequency at all three locations. An integrated finite element model was then constructed using Timoschenko beam elements and lumped mass formulation to model the transition piece capped monopiles. The importance of the soil-structure interaction was studied by benchmarking the measurements against numerical results from API method and API method corrected for large diameter monopiles.
Shear Thinning Fluid for Shallow Fracture Formation
Authors: Al-Rashead Mohammed , Al-Yami Abdullah , Al-Arfaj Mohammad , Ba Hamdan Abdulaziz , Khan Majad , Tahir Muhammad Nawaz
Published: August 2024

Drilling fluids (water based or oil based) are used to drill wells. Water based drilling fluid utilize fresh water, seawater, or brines. Selection of optimum chemicals are critical to maximize well’s productivity and reduces drilling cost without damaging equipment or the surrounding environment. Drilling fluids need to be evaluated prior to drilling to ensure technical and environmental requirements. There is always a strong relation between the performance of wells to the chemicals used in drilling and completion. Different polymers are used to control filtration loss, viscosity and shale stabilization.

The objective of this study is to formulate low temperature water-based fluid that develop thixotropic properties at static conditions. The thixotropic conditions at static conditions is achieved at low temperature, which help in mitigating losses when drilling operations is suspended. Inorganic cross linkers trigger the thixotropic performance at static conditions. Inorganic trivalent metals cross linkers have been used since 1970. Cross linkers such as Cr (III) and Al (III) are used in operations such as fracturing. However, the issue with the inorganic cross linkers is the stability under high temperature (more than 90 °C). Such temperature limitation makes such thixotropic fluids ideal to drill through fractured shallow formation. A different study will address required modification to extend the temperature stability to be used in higher temperature formations.

Standard performance for drilling fluids include: fluids preparation, density and rheological properties, HT/HP filtration, pH measurement, thermal stability and contamination testing. Different types of salts were tested for additional compatibility testing. The resulted formulations have shown outstanding rheology and fluid loss control at low temperature at low-density ranges.
Enhancing Subsea Ball Valve Performance: A Material and Design Approach
Authors: Ahmadli Mehman , Gjersvik Tor Berge Stray , Sangesland Sigbjørn , Reynes Christian
Published: August 2024

Subsea field development is an important aspect of offshore oil and gas operations. One of the key components in the production system is the subsea actuated valves, installed on Christmas trees and manifolds to control the produced fluid flow from the well to the manifold, and then to onshore facilities or vessels. With the shift towards All Electric Control Systems (AES) in subsea operations, ball type subsea valves could be seen as a better fit for electric actuation since they operate with rotational movement, which aligns well with electric actuation mechanisms, eliminating the need to convert rotational movement to axial movement as in rising stem gate type valves. However, with the current use of tungsten carbide (WC) based coatings on the contact surfaces and sealings, the friction forces, and consequently the required power for actuation, are quite high. This leads to an extended valve opening duration which exposes the internal parts, especially the seals, to solid particles in the fluid. This results in a high wear and damage rate of the valve components over time and eventually the risk of sealing failure.

Initial lab tests from ongoing research activity on enhancing the material and coatings of the contact surfaces have shown a promising coefficient of friction of 0.08. To quantify the possible force and power reduction through material innovation, a 3D model of the 12-inch subsea ball valve is created, and the model includes different variations of the valve designs depending on the seat type. The models are exposed to different pressurizing scenarios and the maximum torque values are determined through finite element analysis. Considering the safety margins, the results show that with the material enhancement the design torque is expected to be reduced by around 25–35% depending on the valve design. This optimization contributes to the transition to AES in subsea operations by addressing the challenges resulted by high power requirements of subsea ball valves.
A Critical Review of the Correlations Used for Predicting the Onset of the Transition Flow Regime in Pipe Flow of Yield Stress Fluids
Authors: Abou-Kassem A. J. , Jing S. , Ghaemi S. , Kuru E.
Published: August 2024

In this paper, we present a critical review of the models used for predicting onset of the transition flow regime in pipe flow of yield stress fluids. Using the experimental data obtained by the Particle Image Velocimetry (PIV) technique, we developed a new methodology to identify the beginning of the transition flow regime in pipe flow of yield stress fluids. The new method was then used to evaluate the accuracy of the existing transition flow regime model predictions. The proposed approach relies on the boundary layer theory to classify flow into laminar and turbulent. The boundary layer theory enables microscopic characterization of the flow transition that translates into a more in-depth fundamental understanding of the transition phenomena. The corresponding literature, experimental validation, and proof of the concept are presented. We investigated 36 possible permutations of Reynolds number (Re) and critical Reynolds number (Recrit.) definitions (i.e., six Re definitions combined with six critical Re definitions), and in none of these cases, the onset of the transition regime was accurately and consistently predicted. It was noted that the percentage difference between the maximum and minimum values of Re, for the same flow rate and fluid properties, ranged between 27% to 58%, based on fluid properties and flow rate combination, mainly because of the subjectivity of the Re definitions. In order to ensure an accurate prediction of the transition zone, test fluids were designed to have a wide range of generalized Reynolds numbers (i.e., 20 to 9000, as defined by the API-RP:13D) within the physical capacity of the experimental facility (i.e. for a given pipe diameter, maximum pressure capacity of the flow loop and maximum available pump flow rate). The yield stress of the test fluids varied from 0.10 to 0.95 Pa (determined by using the nonlinear curve fitting technique recommended by the API RP:13-D). Results indicated that most of the current transition criteria for the pipe flow of yield power law (YPL) fluids have low accuracy and lack of consistency to predict the onset of the actual transition regime as compared to the data measured by using the PIV technique. This was regardless of the Reynolds number definition used. The proposed PIV measurement-based criterion provides an objective measure that can be used to develop more accurate future transition models or improve the accuracy of existing transition criteria.
Truncation Analysis of Mooring System and Physical Model Test Validation
Authors: Li Ying , Xie Dongxu
Published: August 2024

For a newly designed platform, performing experiments to investigate its motion performances is of significant importance. However, due to the dimension limitation of wave basins, mooring systems in deep waters cannot be modeled in the wave basin with a reasonable model scale. To overcome this limitation, hybrid model tests are carried out with truncated mooring systems. Truncation designs for mooring system are generally based on optimization algorithms as they can improve the accuracy of truncation. An effective dynamic truncation method based on golden-sine dynamic marine predator algorithm (GDMPA) is proposed in this work. A truncated design for the mooring system was conducted on a conceptual semi-submersible platform located in the South China Sea at a water depth of 1500 m, and experiments were carried out according to the truncated mooring system. The results are compared with those obtained from the truncated design based on the NSGA-II. It is found that the proposed method based on GDMPA is accurate and robust.
Hydroelastic Responses of Submersible Seaweed Cultivation Platforms With Single-Point Mooring Systems
Authors: Nguyen H. P. , Wang C. M. , von Herzen B. , Huang C.
Published: August 2024

This paper presents simulated and realized designs for a submersible seaweed platform capable of deep cycling to water depths beyond 100 meters. The platform is composed of a bundle of two ring structures made of high-density polyethylene (HDPE) pipes filled with seawater to support seaweed grow-out lines. The platform is kept in position by a single-point mooring system. Winches attached to supporting buoys are used to lower weights that help lower the HDPE ring structure to the desired water depth. The platforms responses under wave action in floating and submerged states are investigated by using the software AquaSim. The numerical results show that the deformed shapes of the simulated seaweed platform are similar to those of physical seaweed platform trialed in Cebu waters in the Philippines by the Climate Foundation. The numerical analysis also indicates that at least three lowering lines held by supporting buoys are needed to prevent excessive deformation and stress concentrations in the platform.
Engineering the Best Storm in a Teacup – Bespoke Metocean Criteria Improve STABLEpipe Outcomes for Offshore Wind Array and Export Cables
Authors: Oliver Isla , Thwaites Jack , Williams Benjamin , Pistani Fabrizio , McGrath Nicholas , Griffiths Terry , Brand Folkert
Published: August 2024

It has been found that for many offshore windfarm projects the STABLEpipe design methodology offers substantial benefits to demonstrating enhanced cable stability compared to conventional methods inherited from the oil and gas industry. It has also been shown that the behavior of subsea pipelines and cables can be quite sensitive to the local ambient and storm ramp-up conditions. On a number of recent offshore windfarm projects, Aurora Offshore Engineering has had the opportunity to develop a bespoke set of ambient and storm metocean design criteria through reanalysis of the project metocean hindcast dataset. This paper undertakes a comparative analysis of the outcomes of the STABLEpipe analysis with both bespoke and DNV-generic metocean timeseries in order to investigate the relative impact of these different approaches on cable stability outcomes.
Computational Performance of IB-LBM Based VIV Simulation Using Python With JAX
Authors: Zhu Haiming , Du Zunfeng , Yang Yuan , Han Muxuan
Published: August 2024

Vortex-induced vibration (VIV) of offshore cylindrical structures is a complex fluid-structure interaction (FSI) phenomenon that needs to be carefully considered in the design of subsea pipelines and risers. Computational fluid dynamics (CFD) methods have been recognized as useful tools for investigating VIV. However, the extensive computational time remains a major barrier to practical applications. This paper presents an ongoing effort to develop an efficient vortex-induced vibration (VIV) simulation model based on the immersed boundary lattice Boltzmann method (IB-LBM). We implemented the method in Python with the JAX framework, which offers a user-friendly interface similar to NumPy while delivering performance comparable to low-level programming languages, especially on GPU platforms. The current defects are discussed. Particularly, we highlight the computational inefficiencies associated with the immersed boundary method. The confined immersed boundary approach is proposed to mitigate this issue, which is found to be effective in reducing the time cost by about 25%.
The Influence of Structural Stiffness and Ice Shape on Impact Loads in Ice-Structure Interaction Experiments
Authors: Müller Franciska , von Bock und Polach Franz , Ehlers Sören
Published: August 2024

Ships that are navigating in waters with ice occurrence are prone to the risk of damage due to ice impact. For assessing the safety of ships it is crucial to predict these loads accurately. Ship hulls have varying structural stiffness due to differences in structural design. The stiffness influences the deformation of the structure during ice impact, which in turn affects both the failure behavior of the ice and the loads experienced by the structure. The aim of this study is to understand how ice responds to variations in structural stiffness in an impact scenario and how the structure is affected by impacting with different ice shapes as well as the interplay of both. Research on this topic is very limited, therefore we seek to address this knowledge gap. This paper presents controlled drop tower experiments with freshwater granular ice of varying shapes impacting structures with different levels of stiffness. Drawing upon prior experience,five different ice shapes were investigated: dome, 10° cone, 30° cone, 30° truncated cone and cylinder. Each of these ice shapes impacted both a quasi-rigid plate and a 3 mm steel plate.The 3 mm plate underwent plastic deformation and was measured before and after the ice impact. The data analysis showcased a significant reliance of the peak load on both the structural stiffness and the shape of the impacting ice. Additionally, the analysis highlighted the considerable impact of ice shape on the magnitude of the maximum plastic deformation in experiments involving ice specimens colliding with the 3 mm plates. Among the ice shapes investigated, the dome-shaped and truncated cone specimens stand out, producing the most pronounced plastic deformation in the plate. The results of this study contribute to the development of predictive numerical models for ice impacts on structures by providing a robust set of validation data.
Comparative Analysis of Non-Welded Wrapped Composite Joints Versus Welded Joints Under Multi-Axial Load Conditions in Offshore Wind Turbine Supporting Structures: A Fatigue Performance Evaluation
Authors: Koetsier Mathieu , Mylonopoulos Vasileios , Wolters Mees , Pavlović Marko
Published: August 2024

Offshore multi-membered structures, such as wind turbine support systems, frequently use Circular Hollow Sections (CHS). These structures face loading scenarios from wind, waves, and tides, resulting in axial forces and bending moments in the connections. Traditional welding methods introduce stress concentrations in the material, necessitating the consideration of Stress Concentration Factors (SCF) in fatigue design and the incorporation of stubs and cans to enhance fatigue life. An innovative alternative, as proposed by TU Delft, involves the use of non-welded Wrapped Composite joints. These joints rely on the interfacial bonding between the composite wrap and the hollow section members to transfer loads. This paper presents a comparative analysis of fatigue performance between experimentally tested wrapped composite joints and the fatigue lifetime prediction of their welded counterparts, addressing combined load conditions. At full-scale and 1/4th of full-scale. The study uses a Hexapod testing machine to evaluate various load scenarios on 1/4th of full-scale, including out-of-plane bending, and combinations of axial tension with bending. Full-scale wrapped composite joint in out-of-plane bending is tested in Cronos at OCAS N.V. Belgium. Results reveal exceptional fatigue resistance of wrapped joints to combined loading when compared to welded joints, showcasing their potential for offshore applications.
Investigation Into Sloshing-Induced Fatigue of Inter-Array Cables Inside a Fixed Offshore Wind Turbine Monopile Foundation
Authors: Siddiqui Mohd Atif , Li Henan , Farnes Knut-Aril , Midttveit Steinar
Published: August 2024

Offshore wind offers a great potential to replace fossil fuel energy sources, the latter being the major source of greenhouse gas emissions contributing to global warming. Size of offshore turbines is increasing (better efficiency), with it the size of supporting monopile (MP) structure increases, and turbines are being installed further offshore (stronger and sustained winds available). These factors can cause water motion of the internal free surface (sloshing) inside the MP to be relatively strong. Here, a 3D sloshing analysis is performed to study the effect on the MP and on internal structures such as inter-array cables (IACs) using a Computational Fluid Dynamics (CFD) solver. Sloshing resonance periods/frequencies are calculated using a theoretical formulation. Forced oscillatory motions of the MP in surge direction are simulated at selected sloshing resonance periods to obtain pressure and velocity on the internal free surface. It is found that loads on the MP and internal structures are within limits. A check for IACs fatigue due to sloshing-induced velocities is performed. Fatigue analysis is performed using an in-house tool Flexstress for Umbilicals (FFU). FFU calculates fatigue by combining global analysis from a specialized slender structures time-domain solver (OrcaFlex) for the IAC with a local cross-section analysis of IAC (UFLEX2D). It is found that sloshing has little effect on cable fatigue life (high fatigue life found).
Ship Manoeuvring Study of a Vessel Transiting a Ship Tunnel
Authors: Ross Andrew , Bruyat Anne , Aspelund Leiv , Hassani Vahid , Simanesew Abushet
Published: August 2024

We present an extensive simulation study focused on the approach to, and transit through, the Stad Ship Tunnel. The study incorporates innovative developments in a simulator tool, utilising results from geospatial modelling of the fjords and tunnel, shallow-water and confined-water hydrodynamics, extended modelling of ship hydrodynamics, both seakeeping and manoeuvring, and incorporating collision-dynamics all in one time-domain code, for the calculation of a diverse set of simulation results that can still be synthesised into manageable results.
Combined High and Low Cycle Fatigue Assessment of Tubular K-Joints With Consideration of Plasticity Accumulation
Authors: Xia Yuxuan , Yue Jingxia , Hu Yuhua
Published: August 2024

Various types of marine engineering structures, such as offshore platforms, often use intersecting tubular joints and are prone to initiate fatigue crack under cyclic loadings. Considering that the actual service process may encounter extreme sea conditions, the fatigue of the tubular joints is often not a simple fatigue problem, but a more complex combined high and low cycle fatigue (CCF) one that should take plasticity accumulation into account.

The traditional hot spot stress (HSS) method often fails to achieve satisfactory results when local stress exceeds yield strength. In this paper, a new CCF model considering the accumulation of plasticity is proposed. A nonlinear kinematic hardening material model of Chaboche was used to characterize the hardening behavior of materials under cyclic loadings. The damage under various loadings is calculated based on the new CCF model. And an assessment of a tubular K-joint was made under extreme loadings with the help of FEM.

Compared with the traditional HSS method, this method takes into account the interaction between various loadings, reflects the material’s kinematic hardening behavior, and can predict the fatigue performance of tubular joints more accurately under potentially extreme sea conditions. This method is also applicable to other forms of marine engineering structures.
Physics-Informed Neural Networks for Modeling Linear Waves
Authors: Sheikholeslami Mohammad , Salehi Saeed , Mao Wengang , Eslamdoost Arash , Nilsson Håkan
Published: August 2024

Numerical simulation of water waves is of essential importance for ships and offshore structures design. One promising new method is the training of Physics-Informed Neural Networks (PINNs) for these simulations. The current study is an attempt to train a PINN architecture to analyze the velocity potential of the flow beneath periodic linear waves. It is shown that the developed PINN architecture predicts the pattern of velocity potential distribution near the free surface. The average error of the predicted pattern compared to the results of the analytical solution is 4.34%. The standard deviation of the error after 10 times retraining of the model is found to be 2.79%. The velocity field of the flow can be calculated by the spatial derivation of the velocity potential field. Therefore, the developed PINN can predict the velocity field of the flow beneath the given free surface with the same accuracy. A sensitivity study revealed that the average error and the standard deviation of the error in the prediction of the velocity potential field are highly influenced by the number of neurons, layers, and collocation points of the PINN architecture. The increase in the number of neurons and number of layers is found to have different effects on the average error and the standard deviation of the error.
The Effect of High Triaxiality in HPHT Polymers Used in Flexible Pipes
Authors: Bonanni Michele , Mintzas Angelos , O’Donnell Brendan , Johnsen Joakim , Roberts Andrew
Published: August 2024

The increasing trend for higher temperature and higher pressure developments places more demanding design requirements on flexible pipes. More sophisticated polymer modelling becomes important in these conditions.

The inner pressure sheath or barrier is the critical pressure containing layer in unbonded flexible pipe. At high temperatures, these materials soften significantly whilst retaining sufficient toughness for standard operation. However, this may result in significant plastic deformation in partially constrained scenarios such as at interfaces between metallic and polymer layers.

Traditionally, inner pressure sheath integrity is managed by limiting global strain and ensuring sufficient remaining barrier layer thickness, as specified in API 17J, or through the addition of additional sacrificial layers (tapes or extrusions) where required. Highly localized polymer strains are not normally considered a risk to product integrity.

A large local plastic deformation in a relatively thick layer may result in significant residual triaxial tension at the interface between the plastic zone and the elastic zone within the polymer. At low temperatures, the normal polymer material stiffening exacerbates the triaxial stress state, potentially creating the conditions for fracture nucleation.

Similar effects may be observed in highly dynamic events, such as rapid decompressions, where the strain rate variation can result in changes in material stiffness analogous to temperature effects.

In this paper this phenomenon is discussed further, describing how Enodo and Baker Hughes have performed material testing, developed material models, finite element simulations and defined failure criteria to predict such failures and provide a safe operating envelope for inner pressure sheath design in high temperature and high pressure scenarios.
Experimental Investigation of Nonlinear Forces on a Monopile Offshore Wind Turbine Foundation Under Directionally Spread Waves
Authors: Ding Haoyu , Zang Jun , Zhao Guangwei , Tang Tianning , Taylor Paul H. , Adcock Thomas A. A. , Dai Saishuai , Ning Dezhi , Chen Lifen , Li Jinxuan , Wang Rongquan
Published: August 2024

Accurate prediction of nonlinear wave loading is crucial for designing marine and offshore structures, yet it remains a challenging task. Prior research has primarily focused on uni-directional extreme sea states, revealing that linear loading cannot accurately represent the total wave forces acting on offshore wind turbine foundations, with significant contributions from high-order harmonics. This study broadens the scope to include multi-directional and bi-directional wave interactions with monopile offshore wind turbine foundations. We use a phase-based harmonic separation method to isolate harmonic components in the presence of complex wave scenarios. This approach allows for the clear delineation of individual harmonics from the total wave force by controlling the phase of incident focused waves. Remarkably, this method shown effective even with multi-directional and bi-directional spreading. The clean separation of individual harmonics enables the estimation of contributions from each harmonic. Our findings are in line with previous research, showing that nonlinear loading can constitute up to 40% of the total under certain wave conditions. We have also observed that wider wave spreading reduces nonlinear high-order harmonics, and uni-directional waves induce the most severe nonlinear forces. These insights emphasize the importance of accounting for high-order nonlinear wave loading in offshore structure design.
Finite Element Analysis of Collapse in Thermoplastic Composite Pipes Under External Pressure
Authors: Freitas Inês S. G. , Sousa José R. M. , C. e Gama Winston , O. de Souza Charlton
Published: August 2024

Rising demand for thermoplastic composite pipes (TCPs) in the oil and gas industry is due to their lightweight, strength, and resistance to stress corrosion cracking (SCC). TCPs are utilized in hybrid flexible pipes, replacing steel armors, particularly in the central core, to withstand pressure in deepwater operations. In this context, this study proposes a finite element model to predict the potential collapse of TCPs under external pressure. The finite element (FE) model was developed using ANSYS®, employing three-dimensional solid elements to represent the layers of the pipes. Parametric analyses were conducted to assess the effects of initial ovalities and explore some laminate combinations. Additionally, some failure criteria for composite materials are employed to predict collapse pressure and compare it with the results derived from the finite element model. In these analyses, lay-ups with higher winding angles have shown improved performance. However, it notes that axial resistance decreases with higher winding angles, emphasizing the importance of fiber orientations due to complex loads in risers. Initial ovality impacts deformation more than the capacity for collapse loads. Finally, the failure criteria aligned well with the FE model, with Tsai-Wu demonstrating better accuracy.
Optimization of Segmented Wave-Maker Control to Generate Spatially Uniform Regular Waves in a Wave Basin by Parallel Simulated Annealing Algorithm
Authors: Ota Daichi , Houtani Hidetaka
Published: August 2024

To ensure the accuracy of the seakeeping test of a model ship, the spatial distribution of regular wave heights generated in a wave basin should be uniform. However, the cylindrical propagation property of the waves generated by the segmented wave maker causes non-uniformity. This study aims to suppress such non-uniformity by optimizing the control amplitudes of the wave makers using “Temperature Parallel Simulated Annealing”. The proposed method was numerically validated for wave generation under three different wave direction conditions in the Actual Sea Model Basin at the National Maritime Research Institute. This basin has a rounded-rectangular shape and is equipped with flap-type wave makers all around the perimeter. The proposed method demonstrates a 57% improvement in the mean absolute error of wave amplitudes at a test zone located in the basin for a wave direction of 90° (generated using flaps arranged at the long side of the basin), 26% improvement for a wave direction of 120° (oblique wave), and 25% improvement for a wave direction of 180° (using the short side flap array) compared to wave generation by the conventional “snake motion” principle.
Experimental Study of the Hydrodynamic Characteristics of the Raft Aquaculture Facilities Around a Windfarm Monopile
Authors: Ai Qing , Cao Jinchao , Jin Lei , Chen Deming , Tang Yanli , Zhao Fenfang , Sheng Huaxiang , Wang Xinxin
Published: August 2024

The hydrodynamic attributes of aquaculture structures play a crucial role in ensuring stability and reliability within complex marine environments. This study focuses on raft aquaculture structures situated in offshore wind farms, with a focus on their interaction with the wind farm monopile. Mooring line tension for these raft aquaculture facilities is investigated under various wave conditions, both with and without the presence of wind farm monopile, utilizing physical model experiments conducted in a wave flume. The study employs physical model experiments to assess the hydrodynamic performance of two prevalent raft aquaculture facilities: the longline raft aquaculture and pontoon raft aquaculture facilities, exposed to varying wave conditions. The experimental results show that the maximum mooring line tension diminishes with lengthening wave periods and increases with higher wave height. Notably, the windfarm monopile exerts a pronounced dampening on wave propagation. In the case of single-row aquaculture facilities utilizing windfarm monopile foundation as the mooring anchor, the mooring line tension of pontoon aquaculture facility experiences a reduction ranging from 16% to 65 %, peaking at a wave steepness of 0.037. Meanwhile, the mooring line tension of the longline aquaculture facility is reduced by 71–82 %, reaching its maximum at a wave steepness of 0.041. Moreover, it is observed that the maximum mooring line tension in multiple-row raft aquaculture facilities is smaller than that in the single-row raft aquaculture facility. This research on the hydrodynamic characteristics of raft aquaculture structures aims to provide scientific guidance for selecting aquaculture structure types in offshore wind farms.
Characterization and Performance Evaluation of Various Types of Polymers Based Latexes for Cementing Application
Authors: Al-Yami Abdullah , Khan Majad , Tahir Muhammad Nawaz , Alsafran Ali , Wagle Vikrant , Almulhim Sara
Published: August 2024

Gas migration through cemented casings may introduce a risk for wellbore integrity if cement formulations do not contain additives such as polymer latex. Polymer latex have been used to help reduce the fluid loss to minimize gas migration, improve wellbore integrity, and aid in the mixing ability of cement slurries. Many theories and mechanisms have been detailed to prevent annular gas flow through a cement column. Cement slurry loses its ability to transmit hydrostatic pressure during the transition from liquid phase to semi-solid phase until complete loss of hydrostatic pressure as cement slurry sets. In high pressure formation, gas or liquids can travel up through cement matrix due to lost hydrostatic pressure. This migration of liquid or gas can cause high surface pressure that may prevent us from fully utilization of these wells.

Similar produced latex is employed as a binding agent in cement used primarily for construction applications. The construction cement is, however, exposed to ambient temperature and pressure conditions. Thus, it is proposed to study the performance of latex used in construction industry for cementing applications at elevated temperature and pressure conditions.

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 in elucidating the structures and physical properties of different latexes. Tests such as thickening time test, fluid loss test, and rheology measurement test were conducted to compare the performance of different latexes in cement slurries.

Different concentrations of polymer latex based on emulsion of polyvinyl acetate were used without success resulting in extreme fluid loss. So, we had to increase the concentration of polyvinyl alcohol in the local PVA by conducting in-situ hydrolysis. We have utilized lime or Ca (OH)2 to achieve this. The result was polyvinyl alcohol and calcium acetate. Treating styrene butadiene polymer-based latex with citric acid extended the thickening time of cement slurries beyond 6 hours which is enough to perform cementing operations for oil and gas wells. As the pH is reduced by the addition of citric acid, thickening time will be longer and fluid loss will be lower. The ability of forming a film to reduce filtration is improved by reducing the deprotonation of the latex in basic solution (less interaction with calcium ions).
Effect of Forward Speed on Hydrodynamic Responses and Structural Responses of a Benchmark Vessel
Authors: Cheng Zhiping , Chen Yingying , Cai Minbo
Published: August 2024

This study first validates the Rankine source model with experimental data, subsequently, conducts hydrodynamic analyses of KVLCC2 at four forward speeds. The effect of forward speed on hydrodynamic responses is evaluated by comparing long-term extreme responses of 6-DOF motions and global section loads. There is a notable increasing trend of surge motion and yaw motion as forward speed increases. Whereas the pitch motion demonstrates the opposite tendency. The influence of forward speed on other motion modes is negligible. As for global section loads, the impact of forward speed on vertical shear forces and vertical bending moments is not significant. While the horizontal shear forces, horizontal bending moments and torsional moments show a downward trend with an increment of forward speed. Whereafter, this paper performs global FE analyses of KVLCC2 at zero forward speed and the design speed (15.5 knots). The comparisons of stress RAO amplitudes of typical structural members indicate that the effect of forward speed on stress amplitudes does not show a consistent trend in different wave conditions. The long-term stochastic analysis and fatigue assessment results reveal that most of the selected structure members experience larger extreme stress responses and more severe fatigue damage in stationary state than in navigating state with the design speed. Whereas, the bulbous bow suffers more severe fatigue damage in navigating state with the design speed.
Dynamic Response of a Steel Catenary Riser at Touch Down Zone With Seabed Trenching Development Considered Under Irregular Waves
Authors: Gao Zhenguo , Zhou Zefeng , Wang Weichen
Published: August 2024

The steel catenary riser (SCR) serves as a primary solution for deep-water oil and gas field development, but it encounters complex dynamics due to forced oscillations induced by wave-driven floater motions, especially at the touch-down zone (TDZ). Traditional pipe-soil models often fail to address these challenges, as they do not account for soil remoulding and the impact of irregular motion. This is particularly relevant in real sea states characterized by irregular waves, where the floater’s movements have a significant impact on seabed trenching, thus complicating the dynamic responses of the SCR. To address these issues, this study integrates an innovative effective-stress-based pipe-soil interaction model into a global SCR analysis to explore its dynamic response and fatigue damage under irregular waves. The irregular movements of the floater, derived from response amplitude operator (RAO) data and wave spectra, are applied to the SCR’s top end after a translation to the hang off location. This allows for dynamic simulations that consider the evolution of the seabed and the process of trenching. The study focuses on deriving the dynamic stresses experienced by the SCR at the TDZ and evaluating fatigue damage using the S-N curve method. It also examines the seabed interaction, including the evolution of trenching, changes in seabed stiffness, and soil resistance at various SCR locations. By considering real sea conditions, this study yields insights into trenching and seabed-SCR interactions, promising to enhance design methodologies and bolster offshore infrastructure performance and safety.
Experimental and Numerical Investigation on Ship Rolling Motion Response Coupled With Liquid Sloshing
Authors: Wang Yunhe , Jiang Shengchao , Zhou Tongming
Published: August 2024

This paper investigates the coupled dynamics of a ship carrier with sloshing inside three liquid tanks at varying filling depths, employing both experimental and numerical methods. Two obvious peaks for ship rolling motion are captured when sloshing exists in the liquid tank. One peak occurs earlier and the other occurs later than the peak of ship rolling motion without sloshing. The coupling motion results reveal the existence of the natural period of sloshing and the natural periods of ship-tank system rolling motion. The natural period of sloshing always corresponds to the trough between the first and the second peak. The biggest difference between the two peaks is the opposite phase relationship between ship-tank motion and the fluid motion inside tanks. The experimental free decay test can only predict one of the two periods (corresponding to the two peaks) of ship rolling motion. A new numerical coupling model is developed and it can simulate the ship motion coupled sloshing precisely.
Benchmarking Measured Eigenfrequencies: A Case Study of a North Sea Offshore Wind Farm
Authors: Sastre Jurado Carlos , Weijtjens Wout , Stuyts Bruno , Winkler Kristof , Fallais Dominik , Devriendt Christof
Published: August 2024

Offshore wind turbines are dynamic structures that require an accurate estimate of the main eigenfrequencies to avoid resonance and, as a result, increased fatigue damage. This contribution focuses on the first and second mode eigenfrequencies measured over an entire offshore wind farm in the Belgian North Sea. The comparison between the field measurements during parked conditions and design estimations yields the same conclusions as previous studies reported in the literature; eigenfrequencies are systematically underestimated. A comprehensive step-by-step fleet-wide numerical benchmark is thus presented to improve the model predictions and understand the causes of the mismatch. Finite-element analyses, based on the current state-of-the-art soil-monopile interaction models, were considered since the foundation stiffness is identified as a key source of the discrepancy between in situ observations and design models. The importance of environmental parameters in the second mode is studied. The consideration of the contribution of scour protection for a realistic representation of foundation stiffness is discussed as well. The final results show that simulations agree considerably better with the measurements, although a significant bias is still observed for the second mode.