bluuebunny/crossref_metadata_2025 huggingface dataset:
Double Braid Mooring Damper for Floating Offshore Wind Application
Authors: Khalid Faryal , Thies Philipp R. , Halswell Peter , Newsam David , Johanning Lars
Published: October 2022

Introduction of innovative mooring components can reduce the risk and cost associated to mooring systems of floating offshore wind turbines. The Intelligent Mooring System (IMS) is an active, hydraulic, nonlinear mooring component developed by Intelligent Moorings Limited that provides functionality akin to a shock absorber. It offers a combination of desirable stiffness characteristics for floating offshore wind application; an initial compliant response that reduces loads on the structure and a stiffer nonlinear response for larger loads to reduce platform motion and ensure effective station keeping. A salient feature of the IMS is that through variation of the internal pressure, the stiffness of the system can be adjusted in accordance with the prevailing environmental conditions.

This paper presents the results of the physical testing of a double braided IMS at the Dynamic Marine Component test facility and compares the stiffness and strength characteristics to a single braid sleeve. The comparative analysis shows that the stiffness profiles of the double braid for the various configurations are consistent with the single braid design. Importantly, the use of a double braid results in a 50% increase of the tensile strength of the IMS. The investigation presented in this paper will aid in the design of a robust IMS for field testing prior to commercial applications in floating wind installations.
The Effects of Hydrodynamic and Aerodynamic Loads on the Low Frequency Responses of Floating Offshore Wind Turbines
Authors: Land Edward , Brindley Will , Hu Zhiqiang
Published: October 2022

To meet the growing demand for renewable energy and net zero carbon emission targets set by respective governments, offshore wind is looking to move into deeper waters using floating offshore wind turbines (FOWTs) to capture the more consistent winds and expand the area available for energy capture. This has presented the challenge of being able to accurately model FOWTs allowing for the design of cost-effective and reliable structures. In recent years, code comparison studies have revealed that current modelling tools and design techniques used in the industry yield a significant underprediction in low frequency forces and responses with respect to the surge and pitch degrees of freedom. This has been attributed to platforms being excited by nonlinear hydrodynamic forces outside of the linear wave excitation region which are not being properly captured by current market available modelling tools. However, other studies have revealed that aerodynamic loading can produce additional low frequency forces which could in combination give dangerously underpredicted structural loads.

This paper looks to examine the underpredicted forces and responses through use of the in-house developed program ‘DARwind’ and the commercial software OrcaFlex, with an emphasis on the surge degree of freedom motion. The calculations are conducted for a range of different analysis settings and loading conditions in order to compare the contribution of low-frequency loads and the responses of FOWT. In addition, wind load in the simulation will also be divided into two conditions, one is for constant wind speed, and the other is for wind spectrum which considers the low-frequency contribution. It was found that whilst both programs used during this study underpredicted low frequency motion, incorporating various theories and semi-empirical corrections helped reduce this underprediction. This work has allowed for a clearer view of the issues surrounding the underprediction of low frequency loads and responses and will assist in furthering research in this area.
Modified Dam-Break Solution for Green Water on the Deck of an FPSO
Authors: Xia Jinzhu , Liu Huaxing , Sukri Hilmi
Published: October 2022

A modified dam-break solution is proposed to predict green water profiles on the deck of an FPSO through calibration against model test results. The dedicated modifications to the original dam-break solution of Ritter (1892) include: the adoption of the measured speed of waterfront propagation on deck and the calibration of the initial speed of negative surge. These modifications are introduced to address the gaps between the classical dam-break theory assumptions and the actual FPSO green water scenarios. Such gaps include the difference between a body of dead water against a removed dam and an event of freeboard exceedance due to isolated wave run-up, the friction of the deck surface, and the effect of vessel motions in severe sea states. The proposed mathematical formulation is applied based on model test results of a specific spread-moored FPSO design. By comparing the predictions with the measured extreme water height and flow speed on deck for scattered transverse locations, the calibration factors are determined and the water height profile as well as the associated horizontal flow speed along a cross-section is obtained. With the model test measurements of a dedicated wave probe array, the 3D mapping of green water elevation and horizontal speed in all concerned deck areas can be produced. This then forms the basis for green water impact prediction for any object and location of interest on the deck.
Investigations On The Effects Of Internal Liquid Sloshing of Semi-Submersible Floating Offshore Wind Turbines
Authors: Zhou Yang , Qian Ling , Bai Wei , Lin Zaibin
Published: October 2022

Originally developed for civil engineering applications, the tuned liquid column damper (TLCD) has been applied not only on tall buildings but also on floating offshore wind turbines (FOWTs) to minimize structural vibrations. This concept has also been adopted widely in navel architecture to reduce the roll motion. However, whether the damper will bring positive effects on mitigating the dynamic motions of FOWTs remains unknown.

To this end, the paper studies the star-like three columns tuned liquid multi-column damper (TLMCD) impacts on the dynamic motions of a semi-submersible FOWT. The modelling is achieved by using a high-fidelity computational fluid dynamic (CFD) solver based on OpenFOAM. After the verification of the numerical model for the TLMCD system, it is extended to the modelling of the internal sloshing of TLMCD under prescribed pitch motions. A fully coupled floating-sloshing modelling is then conducted to simulate a semi-submersible FOWT with an integrated TLMCD under regular wave conditions. The study indicates that the passive-control TLMCD system has nearly no influence on the translational motions such as surge and heave. However, the pitch motions can be reduced significantly when the incident wave frequency is close to the natural pitch frequency of the platform. Apart from the natural pitch frequency, the TLMCD has a minor effect at other incident wave frequencies.
Treating Agent for Reducing Adsorption Damage of Slick Water on Coal Rock Surface
Authors: Wu Guodong , Li Bojun , Anwaier Maieryemuguli , Li Yuan , Ren Hongda , Yao Erdong
Published: October 2022

Hydraulic fracturing is generally required for coalbed methane to achieve economic production. Slickwater fracturing is one of the most commonly used technology. During fracturing, a million gallons of slickwater are pumped downhole to create fractures, and lots of fluid would filtrate into the formation matrix. The polymers in the fracturing fluid will be absorbed in the porous medium of coal rocks and then decrease the permeability of the reservoir. This paper studies the adsorption amount and the form of slickwater on the coal seam surface and proposes a method to relieve slickwater damage. First, we tested the damage of coal rocks caused by slickwater of different molecular weights. Then the adsorption capacity of different types of slickwater was measured through static adsorption experiments. The changes in adsorption morphology was analyzed according to the micro-morphology of the scanning electron microscope (SEM). Finally, the effect and mechanism of the adsorption release agent were discussed. The study shows that coal seam reservoirs block the gas-liquid percolation channels by forming a water film and polymer adhesion in the pore throat by adsorbing the slick water, resulting in a decrease in permeability and affecting subsequent drainage and gas recovery processes, thereby increasing the damage of slickwater to coal rock. After the improvement of the nano-emulsion NLR, the coal core injury removal rate reached 27.75%, the “gas-liquid-solid” static contact angle of the coal chips was reduced from 129° to 107°, and the surface hydrophilicity was weakened. Adsorption morphology changed from flat and smooth to a rough structure. NMR results prove that NLR reduces adsorption and retention.
Short-Term Analysis of Ship Capsizing Probability in Random Seas
Authors: Chai Wei , He Lin , Leira Bernt J. , Sinsabvarodom Chana , Feng Peiyuan
Published: October 2022

Excessive roll motion in realistic seas is one of the main reasons leading to ship capsizing. However, ship capsizing is a rare event for most of the sea states and prediction of ship capsizing probability is still a challenge. In this work, excessive roll motion for the cases of the dead ship condition and the parametric rolling are studied. Specifically, ship roll response in random seas is calculated by numerical analysis, and a stochastic process, X(t), is defined as the absolute value of the roll motion because the capsizing event can be caused by exceedance of the maximum angle at either side. Two different methods, i.e. the traditional Gumbel method and the average conditional exceedance rate (ACER) method are applied in order to predict the extreme values of the stochastic process X(t). The exceedance probability for X(t) corresponding to the critical levels, such as the flooding angle, can then be employed as an equivalent measure of the ship capsizing probability for a given sea state. The relative merits of the ACER method and the Gumbel method will be compared with Monte Carlo simulation. The studies in this work are intend to promote the understanding of ship capsizing in random seas.
Efficient Long-Term Extreme Response Analysis of Floating Bridges Using Multiple Timescale Spectral Analysis
Authors: Fenerci Aksel , Geuzaine Margaux , Denoël Vincent , Øiseth Ole
Published: October 2022

Floating pontoon bridges offer viable alternatives to cable-supported bridges when crossing long straits. Design of such large floating structures requires estimation of long-term load effects (e.g. 100years) under stochastic wave loading. The long-term extreme response of such floating structures can be estimated using the so-called full-long term method, where the structural response is calculated for all possible environmental conditions over a long-term period. Such a procedure is naturally computationally demanding and depends highly on the computational efficiency of the short-term response calculation. Although the procedure is rather efficient in frequency domain compared to time domain, the computational demand can still be considerable when the number of environmental variables is large. Here, we shall explore the possibility of carrying out the short-term response calculations using multiple timescale spectral analysis, which allows analytical approximations of the short-term response statistics. Through comparisons with the more time-consuming numerical solution, we report reasonably accurate estimations with a significant gain in the computational effort.
New Design Methods for Subsea Power Cables Are Helping the Global Marine Renewable Energy Industry Lower Costs and Improve Reliability
Authors: Griffiths Terry , Draper Scott , Cheng Liang , An Hongwei , Schläppy Marie-Lise , Tong Feifei , Fogliani Antonino , Lipski Wacek , Spradbery Chas , Teng Yunfei , White David , Coles Daniel , Noble Stuart , Doole Siobhan , Johnson Fraser
Published: October 2022

University of Western Australia’s Oceans Graduate School to transform the design methods used to analyse the on-bottom stability of subsea power cables. These cables form the vital connection enabling renewable energy to be reliably and cost-effectively transported from the source to the consumer — whether the collection device at the end of the line is wave, tidal, fixed or floating wind. These novel design methods are equally applicable to umbilicals and other small diameter pipelines. Existing oil and gas pipeline codes overlook much of the physics that is relevant to small diameter pipes and cables. The new research has unlocked significant improvements through new laboratory, numerical and field observational analysis and modelling. The results of this research are presently being incorporated into new design guidance, including the draft British Standards Institute BS 10009 being developed under PEL 114 technical committee guidance.

This paper provides a summary of the research together with observations and lessons learnt in the application of these new design methods to over 7.4 GW of new offshore wind and other renewable energy cables. Given that as at 2020 the global grid-connected total offshore wind capacity was 35 GW, this contribution demonstrates strong evidence of field validation of these research outcomes, as well as their relative importance and transformative potential to contribute to global decarbonisation.
Hydrodynamic Performance of Floating Pontoon Type Breakwater With Skirt Walls and Different Porosity
Authors: Neelamani Subramaniam , AlRagum Alanoud
Published: October 2022

Floating breakwaters (FBW) are widely used in moderate wave climatic conditions. Literature shows that the width of a pontoon type FBW should be about 50% of the incident wavelength in order to achieve 50% wave height reduction at the lee side of the FBW. Hence, for a typical wavelength of 40 m, the width of pontoon FBW needed is about 20 m. Such a FBW may not be cost competitive. Is it possible to reduce the width of the pontoon FBW significantly by adding skirt walls (single, twin, triple or five) under the keel. What will be the effect on mooring forces? In order to get solutions for this problem, experimental investigations were carried out on a typical pontoon type FBW as well as pontoon with skirt walls. Both opaque and porous skirt walls are used. Wave transmission, reflection and mooring forces on both the seaside and lee side are measured. It was found from this study that it is possible to reduce the width of the pontoon by 20 to 40% by introducing three or five skirt walls. However, introducing skirt walls is found to increase the mooring forces by 10 to 30%. A US patent (Patent No. US 9,340,940 B2 dated 17 May 2016) is obtained for the novelty of this study.
Preliminary Experiments for Construction of an Evaluation Model for Methane Hydrate Transportation
Authors: Yamamoto Joji , Nakajima Yasuharu , Yamamoto Marcio , Takano Satoru , Ono Masao , Kanada Shigeo , Otsubo Kazuhisa
Published: October 2022

Methane hydrate has been found below the seafloor in Japan’s Exclusive Economic Zone (EEZ) in a large amount. During the methane hydrate transportation, it is concerned that the riser pipe or the flowline can be plugged by the hydrate reformation and the freezing of seawater. The degradation and reformation kinetics of methane hydrate are mainly controlled by temperature, pressure, and methane concentration in the system, however, it is difficult to predict these factors in the multiphase flow because they are affected by fluid dynamics and heat transfer. Therefore, we are currently constructing an evaluation model for the slurry transportation, including the formation and dissociation processes of the hydrate in a riser pipe at dynamic conditions. Then, the characteristics of the phase change by the hydrate’s formation and dissociation have been investigated using experimental apparatus simulating the flow situations in a riser pipe.

This paper reports some data obtained in two preliminary experiments on the heat transfer effect of pipes and the hydrate formation process. The formation processes of gas hydrate at a gas-liquid interface under high-pressure conditions were observed by using a probe-type video camera. The experimental results showed that the formation of gas hydrate requires enough amount of gas injection, including the dissolved gas in seawater, in addition to temperature-pressure condition.
Lazy Wave Riser Slug Induced Vibration - Modelling Validation
Authors: Minguez Matthieu , Le Prin Kevin , Jara Bravo Cristian , Liné Alain , Cinello Alexandre , Rippol Thierry
Published: October 2022

The paper addresses the mechanical response of a lazy-wave riser system (either rigid or flexible) subject to internal intermittent slug flows. This work makes echo to previous papers (OMAE2020-18620, OMAE2021-60717) proposing novelty and additional features to be either considered in front-end or detailed engineering phases. The focus point of all these studies is the validation of the proposed numerical models to assess the fatigue induced by such complex coupled physics.

This numerical approach suggests coupling both multi-phases flow and mechanical solvers to recover the complex riser response. The coupling is ensured in both time and space to account for the variability of the slug flow properties along the riser. For validation purpose, a large-scale model test (19m long, 2″ diameter) is proposed to (i) characterize the internal slug flow properties along the riser and (ii) monitor the mechanical riser response.

The rough data coming from the large-scale model tests have firstly been exhaustively post-processed to confront the observed internal flow regimes at different locations with some well-known empirical formulations. Then, they are used to discuss the variability of the flow properties along the riser system.

Finally, the proposed coupled modelling is confronted to the experimental data. A very good match is obtained considering the proposed modelling for a large range of flow conditions when comparing the dynamic response of the riser. In the meantime, a simplified method is also introduced and validated for preliminary screening analysis.
The Influence of Added Mass in Ship-Ice-Wave Interactions: A Potential Flow Hydromechanics Model
Authors: Jiang Zongyu , Li Fang , Mikkola Tommi , Kujala Pentti , Hirdaris Spyros
Published: October 2022

For ships navigating in ice floe fields, ship-ice-wave interactions may have significant influence on ship performance and ice impact forces. This is because added mass may affect the hydrodynamic interaction between a ship with ice floes. This paper explores the influence of added mass using a Boundary Element Method (BEM). The model considers the effects of wave frequencies and propagation that are ignored by the conventional Popov (1967) method. Preliminary results are presented for a regular waves scenario whereby a Wigley hull passes by a freely floating ice floe modelled as a round disk. A parametric analysis on the effects of the added mass demonstrates the importance of accounting for multibody interactions.
Application of Artificial Intelligence for VIV Strake Optimization of Steel Lazy Wave Risers
Authors: Lal Mayank , Sebastian Abhilash , Rana Yashpal
Published: October 2022

Vortex Induced Vibrations (VIV) may cause significant fatigue damage in Steel Lazy Wave Risers. The severity of the VIV fatigue damage is dependent on the natural frequency of the riser and the vortex shedding frequency which varies according to long-term current profiles and distribution. VIV suppression devices such as strakes, fairings and integrally straked buoyancy modules are used on riser pipe to reduce the fatigue damage caused by vortex induced vibrations. However, the higher the coverage of these suppression devices, the higher the Engineering, Procurement, Construction and Installation (EPCI) cost of the riser.

Strakes are the most commonly used suppression devices for deep water risers. The buoyancy section of the Steel Lazy Wave Riser needs to be straked if it becomes a driving power in region for vortex induced vibrations. As VIV strake coverage increases, the installation time for the riser increases which can significantly affect the EPCI cost of a riser due to the high day rate of installation vessel. Hence optimizing the coverage of strakes can result in significant savings. Typical strake coverages on risers can range from 30–90% of riser suspended length for Gulf of Mexico projects while in South America it can range up to 100% including the buoyancy region.

Genetic algorithm is applied within an artificial intelligence tool to optimize the coverage and location of strakes along the riser automatically using an objective function with the aim of minimizing the strake coverage length. The algorithm for the proposed artificial intelligence tool along with the objective function are presented in the paper followed by a few examples showing the efficacy of the tool. While optimizing the coverage and location of strakes on risers is an iterative and cumbersome process, the use of the artificial intelligence tool presented in this paper will help an engineer speed up the strake coverage design and improve the quality of VIV analysis performed together with savings on EPCI cost of steel lazy wave risers.
Influence on Sealing Integrity by Pressurization During Cement Sheath Setting
Authors: Wu Xuning , Li Zaoyuan , Liu Jian , Hou Zhengmeng , Su Donghua , Li Jin
Published: October 2022

After cement slurry is injected into the a well, weight loss will occur before the cement sheath is formed, so that the pressure of the cement slurry column will gradually decrease, which will increase the risk of micro annulars at the casing-cement sheath-formation interface. In this study, one cement sheath sealing integrity test platform integrated with curing and testing was established to simulate the hydration weight loss process in the cement sheath setting. The sealing integrity of the cement sheath under stage pressurization and rapid depressurization was tested. Using the theory of thick-walled cylinder of an elastoplastic mechanics, the development of the elastoplastic interface of the cement sheath under the change of casing internal pressure was calculated, and the calculation method of equivalent crack width were established. The research results show that, the greater the setting pressure loaded during the curing process on the cement sheath, the higher the stress that the cement sheath can withstand during the later operation. After the cement sheath body is destroyed, as the internal pressure of the casing decreases, the width of the micro cracks increases. The research results of this paper can provide an important reference for designing mechanical properties of cement sheaths and improving the sealing ability of cement sheaths.
The Influence of Directional Well Azimuth on Bit Performance: A Statistical Approach
Authors: Nour Muhammad , Farahat Mohamed S. , Mahmoud Omar
Published: October 2022

The drilling cost represents a significant portion of total well cost, especially for directional wells. The major component of drilling cost is determined by how fast a well is drilled, i.e., rate of penetration (ROP). Many factors affect ROP including bit type and condition, formation characteristics, and drilling parameters. One factor that is usually ignored is the direction of drilling (well azimuth). Literature introduces many thoughts about effect of well azimuth on important issues like wellbore stability, but unfortunately it lacks high quality researches about azimuth/performance relationship. The objective of this paper is to test the influence of drilling azimuth on drilling performance.

This relationship was studied in terms of ROP, and drillability exponent (DEXP), which can be used for drilling performance assessment besides well control applications. Drilling data from different areas was processed and categorized by fields and formations. In-Depth statistical analysis was performed, and visualization tools like heat maps were generated to assess the relationship between drilling performance and drilling azimuth. The noise effect of various factors like bit type and condition was normalized so that the resultant output was expressive of azimuth effect.

The resultant heat maps act in the same manner as mechanical earth models (MEM) were used for wellbore stability studies. This occurs by suggesting the most appropriate azimuth to drill the well more efficiently in terms of time and power consumption. Python libraries were implemented for the sake of fast data processing with visually comprehensible output reports that were used for the planning of future drilling campaigns. These reports have ROP and DEXP graphed against well azimuth and inclination to magnify the effect of both horizontal earth stresses and attack angle of the bit. Although the output is conclusive in most cases, this is not the fact in all wells and further investigations are required.

The result of this research is very beneficial tool that can be used while planning directional trajectory of oil and gas wells to speed up the drilling operations and cutting the cost back. By allocating suitable targets to certain surface locations, the required horsepower to drill the well at the same ROP is reduced and the rig time at the same power is significantly cut.
A Numerical Investigation on Flow Induced Vibration of Flexible Risers in Tandem Arrangements
Authors: Periyal Arun , Ghoshal Ritwik , Joshi Vaibhav
Published: October 2022

In this work, a numerical simulation of flow-induced vibrations (FIV) of two tandem long flexible cylinders is performed. In this regard, a fluid-structure interaction solver that uses a partitioned iterative formulation for coupling between the nonmatching 3D fluid mesh elements and the 1D beam elements is carried out through conservative surface-to-line coupling and vice-versa. Simulations are performed for two identical cylinders with an aspect ratio of 350 and a mass ratio of 1.9 which are subjected to a uniform with a Reynolds number of 6400. Simulations are carried out for various gap ratios ranging from a low gap ratio of 8 to a very high gap ratio of 16. The displacement time history of both the flexible cylinders is computed in both cross-flow (CF) and in-line (IL) directions. It is observed that the FIV response of the upstream cylinder roughly resembles the typical vortex-induced vibration response of a single/isolated flexible cylinder. The upstream riser vibrates with lower amplitude as a result of high reduced velocity, away from the synchronization regime. However, due to the interaction of the downstream riser with the disturbed wake of the upstream riser, its amplitude is observed to be higher, indicating resonance with the vortex shedding frequency and high amplitude vortex-induced vibrations. The shielding effects experienced by the downstream cylinder due to the wake generated from the upstream cylinder and its concomitant effect on the response of the riser have been studied thoroughly for different gap ratios. Investigation on dominant frequencies, the trajectory of the riser, and flow analysis of the interacting vortices are also performed in this study.
A Reduced Order Parameterization of Random Wave Fields With Deterministic Wave Groups
Authors: Tang Tianning , Adcock Thomas A. A.
Published: October 2022

Under a linear model of gravity wave evolution the expected shape of large events is given by Quasi-determinism theory. However, nonlinear physics modifies the averaged shape of the largest events. In this study, we examine these nonlinear modifications to the averaged shape of the largest events for directionally spread random wave fields. We first compare these nonlinear changes from the extreme events in random wave fields with the nonlinear changes during the evolution of deterministic wave groups. We then explore whether it is possible to predict these nonlinear changes observed in random wave fields with only nonlinear wave group simulations. We applied a modified version of the wave group detection algorithm in [1, 2] to isolate the individual wave groups from random wave fields. We perform the nonlinear wave group simulations with the initial conditions matching these isolated individual wave groups extracted from linear random wave field. The nonlinear evolution of these isolated wave groups can predict the envelope contraction of averaged shape of extreme events in random wave fields quantitatively over a wide range of local steepness under current conditions. This suggests some statistical connections between the nonlinear evolution of deterministic wave groups and the evolution of the largest waves in the random wave fields.
Offshore Wind Farms and Isolated Oil and Gas Platforms: Perspectives and Possibilities
Authors: Mota Daniel dos Santos , Alves Erick Fernando , Sanchez-Acevedo Santiago , Svendsen Harald G. , Tedeschi Elisabetta
Published: October 2022

Single-cycle gas turbines operating at low-efficiency ranges due to redundancy concerns in offshore oil and gas platforms are responsible for considerable amounts of nitrogen oxides and greenhouse gas emissions in some countries. The abundant resource of offshore wind energy constitutes an extraordinary opportunity for reducing such emissions. However, new challenges are introduced when gas-powered generation is partially replaced by wind power. This paper investigates the possibilities provided by a centralized hybrid energy storage system (ESS) for addressing these challenges. It reviews frequency control concepts for isolated grids and discusses the analogous problem of power balancing within the ESS itself. A set of structures for control of the grid frequency and the ESS DC voltage are described and evaluated. All illustrated by results obtained within the frameworks of the Innovative Hybrid Energy System for Stable Power and Heat Supply in Offshore O&G Installation Project and the LowEmission Research Centre.
Enhancements of Computational Fluid Dynamics Analysis of Air Entrapment and Fluid-Structure Interaction During Plate Entry to Water Through VoF-Slip and Adaptive Discretization Schemes
Authors: Mucha Philipp , Jiang Minyee , Bay Raymond J.
Published: October 2022

A Computational Fluid Dynamics (CFD) analysis of air entrapment and structural response during flat plate entry to water is presented. Slamming loads remain of concern for the design of safe and efficient ships and offshore structures to ensure structural integrity during extreme. Besides ships with large bow flare or horizontal stern planes, slamming events also occur for fast small craft with stepped hulls. Ditching of airplanes and vehicle wading represent non-marine applications. The advance of computational methods in engineering has enabled fluid-structure interaction (FSI) simulations for slamming. A crucial task of solving the coupled fluid and structural problem is the accurate resolution of free surface dynamics and phase interactions between water and air. Numerical ventilation on the bottom plating can arise due to discretization issues and curtail the resolution of physical aeration effects. The study at hand was based on a Finite-Volume (FV) method and the numerical solution of Reynolds-averaged Navier-Stokes (RANS) equations. Emphasis was laid on numerical techniques to contain numerical ventilation whilst limiting the increase in computational cost. In doing so, adaptive discretization schemes were employed. Namely, model-based adaptive mesh refinement (AMR) and time stepping for both motions of bodies (rigid and elastic) and the free surface. Additionally, the underlying Volume of Fluid (VoF) method was enhanced through consideration of slip between water and air to improve air entrapment predictions. Comparison was drawn to a novel experimental analysis for which both structural responses and high-resolution imagery of aeration were available. It was demonstrated that above enhancements not only lead to better capturing of air entrapment and reduced numerical ventilation, but also offered more flexible modeling concepts and potential performance gains.
Correlation/Prediction of CO2 Solubility in Single-Salt and Multi-Salt Brines Using PR EOS Incorporated With Modified Alpha Functions and BIP Correlations
Authors: Chen Zehua , Yang Daoyong
Published: October 2022

Accurate prediction of CO2 solubility in brine is of high significance for carbon capture, utilization, and storage (CCUS); however, no generalized methodology has been made available to successfully tackle such a technical challenge. In this study, a pragmatic and robust technique has been developed and generalized to correlate the CO2 solubility in single-salt brines using the Peng-Robinson equation of state (PR EOS) together with the modified alpha functions and binary interaction parameter (BIP) correlations. A comprehensive CO2 solubility database is firstly built to cover a large range of temperatures, pressures, salt concentrations, while five different salts (i.e., NaCl, KCl, CaCl2, MgCl2, and Na2SO4) are involved. By integrating with the modified alpha functions and BIP correlations, such a generalized model is found to yield an average absolute relative deviation (AARD) of 5.24%, 5.82%, 7.64%, 6.04%, and 4.61% for the correlated CO2 solubility in the aforementioned five single-salt brines, respectively. Compared with the existing correlations, the PR EOS-based model is better than the existing OLI, SP 2010, and DS 2006 models but only slightly inferior to the PSUCO2 model under certain conditions. By combining a new BIP correlation, the newly proposed model has been extended to predict the CO2 solubility in multi-salt brines with an AARD of 7.21%. In addition to its simplicity and high accuracy, this new model can be used to not only determine other physical properties including density, enthalpy, and interfacial tension of CO2-brine systems, but seamlessly integrate with any reservoir simulators, allowing for accurately evaluating and predicting performance of CO2 enhanced oil recovery and storage capacity under various conditions.
Fatigue Performance of Thermal Spray Aluminium Coated Mooring Chains
Authors: Fernandez Jonathan , Arredondo Alberto , Albisu Beatriz , Exposito Aintzane , Rodríguez Elena , Arana José Luis
Published: October 2022

Corrosion-fatigue is the main damage mechanism of chains in permanent mooring systems. Fatigue loading is unavoidable, but corrosion can be mitigated or prevented; so, the impact of its reduction in the corrosion-fatigue damage mechanism is of great interest.

TSA (Thermal Spray Aluminium) coating has been applied for corrosion mitigation in mooring chains, typically at the splash zone, where higher corrosion rates are expected compared to those in submerged condition. TSA coating was first applied in mooring chains in 2001 at the Gulf of Mexico. This early experience of TSA demonstrated its effectiveness in preventing corrosion of top chains and led to several projects applying TSA in the same location.

However, TSA’s effect on the fatigue performance of mooring chains had not been investigated so far. The paper presents full scale fatigue test results of TSA coated mooring chains. Six fatigue tests have been carried out on 76 mm chain, which results show increased fatigue endurance relative to comparable fatigue test data of freely corroding chains in seawater. The results are statistically analysed and compared with all available test data of uncoated chains from Joint Industry Projects, in order to assess the effect of the coating in the fatigue strength of mooring chains.
Development of New Inhibited Spacer for Cementing Operation
Authors: Alkhalaf Sara , Al-Yami Abdullah , Wagle Vikrant , Al-Safran Ali
Published: October 2022

Spacers are a very important element to have good cement bonding and to ensure well integrity. Spacers are used to prevent the contamination of the cement slurry by removing such materials and pushing them ahead toward the surface to separate the drilling fluid from the cement slurry. During the cement displacement process, and once the clay formation is in contact with the water present in the cement slurry, shales will be swelled or cracked due to the hydration reaction or water adsorption.

Therefore, it is very helpful to make a spacer with efficient properties that help in protecting the clay formation from the water and prevent or minimize the hydration process by adding shale inhibiter to the spacer mixture formula. In this study, we will investigate the impact of KCL and a novel amine-based shale inhibitor on clay formation and investigate how these chemicals work to enhance spacer functions. The spacer has to be compatible with the drilling fluid and the cement slurry at the same time. Our study includes the compatibility test, rheology, thickening time test, as well as dispersion test for both KCl and novel amine based shale inhibitors.
Estimation of Design Slamming Loads From Laboratory Test of a Circular Cylinder
Authors: Lian Gunnar , Haver Sverre , Swan Chris
Published: October 2022

Slamming from steep breaking waves can give high impact loads, both globally and locally. In this study we quantify the difference between slamming loads in long-crested and short-crested seas by performing model tests in 11 different sea states. The q-probability slamming load is estimated from long-term analysis by utilizing a modified version of the all-sea state approach where we integrate over a limited domain of sea states. The selected domain includes the sea states that contribute most to the characteristic design value. This method is convenient if the response needs to be estimated by model testing in a limited number of sea states.
Hydrodynamic Analysis of a Triple Thruster Unit Via a BEM/RANS Interactive Method
Authors: Kim Seungnam , Kinnas Spyros A. , Grebstad Ray Thomas , Johannessen Jahn Terje
Published: October 2022

In this paper, a boundary element method (BEM) is used to predict the unsteady performance of ducted propellers in open water and ship behind conditions. The model propeller adopted includes the non-axisymmetric duct appendages (e.g., gearbox, brackets, and vertical structure connected to the hub), which induce severe shedding vortices on the propeller plane. This study thus investigates the effects of separation from the duct appendages as well as the upstream hull on the unsteady ducted propeller performance under different loading conditions. To improve the accuracy of a potential flow solver for highly viscous problems with separated flow near a blunt body, the present method is coupled with a viscous Reynolds-Averaged Navier-Stokes (RANS) solver. The former solves the ducted propeller problem to produce the propeller-induced flow field and body forces, with which the latter solves the total flow field based on a finite volume method. This approach is implemented in an iterative manner until the predicted 3D effective wake on the propeller surface becomes fully converged. An automated interface is developed to facilitate this process. A complete analysis of the propeller performance (i.e., predicted effective wake, flow-field, unsteady forces, and circulations on the blade) is presented at various operating conditions to investigate how the flow field inside and outside the nozzle is influenced by the viscous interaction among the incoming flow, propeller, its appendages, and upstream hull. For the sake of validation, the predicted results are compared with experimental measurements and results from unsteady full-blown RANS simulations. The presented results show satisfactory agreement among the results from different approaches, which makes the BEM/RANS coupling scheme adequate and computationally efficient for practical applications.
Development of a Geopolymer Cement for Primary Well Cementing: Method, Preparation and Particle Size Effect on Reaction Reactivity
Authors: Alanqari Khawlah , Al-Yami Abdullah , Wagle Vikrant
Published: October 2022

The global production of cement is the third largest source of CO2 emissions into the environment, which comes from the decomposition of carbonates. Geopolymer cements can reduce CO2 emissions by 64–80% compared to conventional cement (OPC). Moreover, geopolymer cements have demonstrated promising mechanical properties in comparison to conventional cements. We successfully developed a novel geopolymer cement utilizing a Saudi Arabian volcanic ash for primary cementing applications for the oil and gas industry. This novel cement was prepared by activating the volcanic ash particles with an alkali solution to undergo a geopolymerization reaction. The volcanic ash (VA) properties can be an obstacle for implementation such as particle size distribution. The objective of this study is to prepare a geopolymer cement with excellent strength and to investigate the effects of VA particle size distribution on the synthesis, setting time and mechanical properties of volcanic ash-based geopolymer cement. For this study, we used medium and fine ashes. For the fine ash, we investigated three different particle sizes (150 μm, 71 μm, and 45 μm). The compressive strength and thickening time were measured and performed at the estimated bottom hole temperature and pressure. Test results indicate that the resulting compressive strength is linearly affected by the average particle size distribution.
Experimental Study of the Drag and Wave-Induced Surge Forces on an Underwater Vehicle Operating Near the Surface
Authors: Suriben Kristia M. , Yeager Kathryn I. , Klamo Joseph T. , Kwon Young W.
Published: October 2022

This paper investigates the steady drag and oscillating wave-induced surge forces on an underwater vehicle caused by near surface operations. We experimentally measured the longitudinal forces on a submerged body with forward speed subject to single regular waves of various lengths. A circular cylinder body with hemispheric end caps was tested in a towing tank with wavemaking capability. Since the drag force is driven by viscous effects and flow separation, and to confirm if either of these affect the surge forces, we also tested the body with flat end faces to force flow separation at the leading edges. Our results show an increase in the calm water component of the drag force for the flat end face geometry and that both end shapes experience an increasing nonlinear wave-induced component of drag as wavelength increases. For the wave-induced surge forces, we observed that viscous effects and forward speed both play, at most, minor rolls as there was no significant difference between the surge forces on the two different end shapes or between stationary bodies and ones with forward speed.
A Stochastic Approach to Short-Term Ocean Wave Forecasting: Preliminary Results Using Data From a Remote Sensing Imaging System
Authors: Mérigaud Alexis , Tona Paolino
Published: October 2022

There is a growing interest in the applications of real-time wave forecasting (RTWF), which consists in predicting physical quantities directly related to waves, such as the free-surface elevation, wave loads, or the motion of a ship, from a few seconds to several minutes in advance, and using measurements updated in real time. Unlike comparable RTWF methods found in the literature, which are based on the solution of the physical wave propagation equations, the present approach, known as SBP (Spectrum-Based Predictor), adopts a rigorous probabilistic view on the wave prediction problem, based on well-established, standard oceanographic assumptions. This paper presents an application of the SBP method to real wave field data coming from a stereoscopic camera system. To the best of the authors’ knowledge, this is the first time stereo wave data are employed to test RTWF algorithms. The data, recorded at a location in Korea, in the Yellow Sea, present some considerable challenges, such as strong current in excess of 1 m/s, steep waves with substantial non-linear components, and large directional spread in the high-frequency range. With some adjustments to the original SBP approach to account for current, several prediction configurations are tested, showing excellent agreement between the experimental prediction performance curves, and those expected from the SBP theory. With an observation range in the order of 100m, and in the wave conditions studied, reasonably accurate predictions can be achieved up to 20s ahead (approximately 3.5 peak wave periods).
Automated Modal Parameters Identification During Ice-Structure Interactions
Authors: Wang Chunlin , Nord Torodd Skjerve , Li Guoyuan
Published: October 2022

Offshore structures are prone to damage caused by ice-induced vibrations. It is presently unknown to what extent different ice conditions change the properties of the structure, such as natural frequency, damping ratio, and mode shape. Understanding the dynamic interaction between ice and structures are important for the operational ability of offshore structures. In this study, the covariance-driven stochastic subspace identification algorithm (SSI-cov) is introduced to identify modal parameters of a scale-model structure during ice-structure interactions. In order to reduce the number of user interactions and inherent bias to the identified modal parameters, we therefore introduce an automated parameter identification approach. First, SSI-cov is used to obtain poles that describe the information: damping ratio, mode shape, etc. After that, a stable criterion is used to pick up stable poles. Finally, Hierarchical clustering is used to cluster poles to identify the natural frequency. The proposed method is able to reduce the many user-intervenes and enables efficient automatic parameter identification. The results show that Hierarchical clustering can render more successful identifications than the slack value-based method among different ice speeds. The results also show changes in the system frequencies for different ice conditions.
Seakeeping Analysis of a GRP Fast Patrol Vessel
Authors: Hydar V. , Boote D. , Vergassola G. , Păcuraru F.
Published: October 2022

In order to convert the “one-off” construction of light alloy fast boats to a more efficient series production, the project of a 25-meter patrol boat, originally built in aluminum, has been completely reviewed, focusing on the structure design in composite material.

As one of the most important targets of the new project is to further increase the speed performance of the original unit, attention has been initially focused on the weight reduction, this goal being particularly challenging because of the change in the construction material. This gave the opportunity to review the design parameters as well, starting from the design acceleration value which has been assessed at first by considering the Classification Society Rules and secondly by a detailed seakeeping analysis carried out by using ANSYS AQWA software and validated by experimental towing tanks tests at MARIN.