bluuebunny/crossref_metadata_2025_split huggingface dataset:
Viscoplastic Fluid Placements in a Confined Geometry With Applications in the Dump Bailing Method in the Plug and Abandonment of Oil and Gas Wells
Authors: Akbari Soheil , Taghavi Seyed Mohammad 
Published: October 2022

Abstract
The plug and abandonment (P&A) operations of oil and gas wells are conducted by placing cement plugs at crucial positions, to preserve the atmosphere and underground water aquifers from the oil and gas migrations. The cement plug should be placed in the wellbore with minimum mixing with the in-place fluid. There are several methods of the cement placement in P&A operations, among which the dump bailing method is one of the most common ones. In this technique, a relatively small amount of cement slurry is released on a bridge plug inside the well and it replaces the in-place wellbore fluids. The dynamics of such a fluid placement is governed by several parameters. In this study, the influence of the yield stress of the injected viscoplastic fluid is analyzed. To do so, the injection of a viscoplastic fluid with low yield stresses into an inclined closed-end pipe (representative of well casing) filled with a light Newtonian fluid is examined. The results show that increasing the yield stress of the injection fluid results in suppressing the mixing between the fluids. The outcomes of this study can be used for enhancing the cementing process in the P&A of the oil and gas wells.
Low Cycle Fatigue in Risers and Pipelines
Authors: Mansour Ghiath (Guy) 
Published: October 2022

Abstract
It is very-well known that fatigue is a primary driver and challenge for steel catenary risers (SCRs) and potentially for steel lazy wave risers (SLWRs) as well. This challenge can be overcome in several ways, some better than others. However, the first step is to predict the fatigue damage properly. Fatigue in risers designed utilizing the working stress design (WSD) method, where stresses are kept below yield, is typically predicted utilizing a stress versus number of cycles to failure (S-N) approach, referred to as high cycle fatigue (HCF). Riser designed utilizing the load and resistance factor design (LRFD), or limit state design (LSD), or strain-based design (SBD) methods are likely to experience yielding and inelastic strains, especially in extreme and survival conditions. Cycles of stresses exceeding yielding and producing inelastic strains occur also in reel-lay operations and are likely to occur in pipelines subjected to large deflections cycles such as over sleepers. Utilizing HCF approach to predict fatigue in this case is inappropriate and a strain versus number of cycles to failure (ε-2N) approach, referred to as low cycle fatigue (LCF), is typically utilized. A detailed approach to predict the LCF fatigue is presented herein along with examples.
Nonlinear Distortion Nature of the Collapse Behaviors for Geometrically Distorted Thin-Walled Hull Girder Subjected to Combined Loads
Authors: Wang Qinghu , Wang Deyu 
Published: October 2022

Abstract
The objective of this research is to reveal the nonlinear distortion nature of the collapse behaviors of geometrically distorted scale models subjected to combined bottom local lateral pressure and hogging moment, aiming at improving the accuracy of the linear scaling law which is currently most used to convert the ultimate strength between geometrically distorted scale models and prototype (CL = 1; Ct = 1). To achieve this aim, firstly, a typical thin-walled hull girder was designed and manufactured, with which a physical collapse test was conducted to experimentally observe its collapse behaviors. Then the physical validation of the finite element model was demonstrated by experimental results. To apply a combined action of bottom local lateral pressure and hogging moment, a similarity criterion of the bottom local lateral pressure was analytically derived based on dimension analysis. After that, a series of geometrically distorted scale models were designed to study the distortion nature of hull girder’s ultimate strength under above combined loads. Finally, for engineering application, we proposed two new scaling criterions for converting the ultimate strength between geometrically distorted scale models and prototype.
Primary Cementing of Horizontal Wellbores With Solid Cutting Beds
Authors: Mitishita Rodrigo S. , Sarmadi Parisa , Waldal Nile , Vogl Anastasia , Frigaard Ian A. 
Published: October 2022

Abstract
We present an experimental and numerical investigation of displacements of viscoplastic fluids in an eccentric, horizontal annulus with a cutting bed left in the well. This problem is of interest to both industrial and academic viewpoints. Firstly, the experiment provides a simplified, analogous effect to a cuttings bed in industrial situations. Secondly, while successful and failed displacements of viscoplastic fluids with various eccentricities have been well documented in the literature, displacements with a blockage in the annular geometry have not been experimentally studied before. We carry out the experiments with a pump driven flow loop with a 7.5m annular test section, with a borosilicate glass outer pipe and stainless steel inner pipe. To model the cutting bed, a solid insert is attached to the narrow side of the annulus. Carbopol solutions, widely known as model yield-stress fluids, are displaced from the blocked annulus. Our protocol consists of direct visualization of the interface between the displaced and displacing fluids with a high-speed camera and UV-lighting setup, along with pressure and flow rate measurements. We compare our experimental data and images with 3D numerical simulations, using a Volume of Fluid method to capture the interface between the fluids. The 3D model provides us with a more detailed analysis of the concentration and velocity profiles, along with comparisons to snapshots of the experimental displacements.
The dynamics of the displacement of two fluids in a horizontal circular annulus is governed by buoyancy, eccentricity and the rheology of the fluids. A positive density difference promotes slumping of the displacing fluid towards the bottom of the annulus. Nevertheless, high eccentricity values (e = 1-standoff) are common due to the weight of the casing pulling downwards, opposing the buoyancy force. Finally, the rheology of the fluids is relevant to determine the presence of un-displaced layers of mud, e.g. at the walls. The same competition described above holds true in the annulus with cutting beds. The blockage incorporates an additional way of altering the velocity field around the annulus. Here we show that the blockage can affect the mud removal in the annular space of the well.
Application of Dipole Damper Panels in Modelling Gap Resonance
Authors: Ommani Babak , Ravinthrakumar Senthuran , Kristiansen Trygve , Olimb Idunn , Lyngvær Bernt Karsten 
Published: October 2022

Abstract
Modelling the fluid response in a gap using conventional frequency domain potential flow solvers is a challenge due to its resonance behavior and the importance of viscous effects. Damping panels, or lids, are usually used to represent the main viscous effects, when more direct method of calculation is not applicable due to limitations on time or computation resources. Although, it is known that the main contributor to the damping is the flow separation at the gap inlet, these methods usually relate the magnitude of the effective damping to the vertical fluid velocity at the surface. In the present study, the application of dipole damping surfaces, as introduced in potential flow code WAMIT, is studied for modelling the flow separation effects more consistently. The relative fluid velocity at the inlet is used to model the damping effect of flow separation. Simplified empirical models are proposed to estimate the magnitude of the damping. The experimental study of flow between two side by side barges by Molin et a. 2009 [1] has been selected to evaluate the present modelling approach. The numerical results show good agreement with the measurements while providing a more consistent basis to apply stochastic linearization of the quadratic damping due to flow separation at the gap inlet.
URANS Predictions of Drift Loads on a Semi Submersible in Steep Waves
Authors: Jaouën Frédérick , Koop Arjen , Bunnik Tim 
Published: October 2022

Abstract
The last decade, many semi-submersible designs have been tested in MARIN’s wave basins as a result of recently modified classification society guidelines requiring to investigate the air-gap of semi-submersibles in waves and the occurrence of wave impacts on deck. The main objective of these tests is to investigate the motions, air-gap and mooring line loads in extreme irregular seas. In several of these model test projects, it was found that accurately predicting the motions of the platform using numerical simulations is not an easy task. Especially, the measured horizontal and vertical low-frequency resonant motions were regularly found to be much larger than predicted by numerical results based on linear potential flow theory. These low-frequency motions are mainly caused by the wave drift loads, i.e. the mean and low-frequency wave loads resulting from the non-linear behavior of the structure in the waves. As these drift loads can be affected by higher than second order effects, model testing is still the preferred method to quantify the loads and resulting motions in survival sea states. However, model test results are most often not available in the early design stage and modifying the design may not be easy when model test results become available, further on in the project. Therefore, the development of a reliable and fast prediction technique would be valuable to improve the design of moored semi-submersibles. Such a method may be CFD, which has the potential to predict the motions and drift loads applied on semi-submersibles in steep waves, without and with the presence of current. To obtain confidence in the accuracy of the CFD results, a validation of these results is essential in the first place.
In this paper, the motions and loads applied on the Stena Don semi-submersible in head-on waves are calculated using MARIN’s CFD code ReFRESCO. The objective is to assess whether the motions and the mean drift loads can be correctly predicted using CFD for regular waves of different steepness. The horizontal drift loads are focused on in this paper. In order to assess the accuracy of the results and the capability of CFD, a stepwise approach has been followed. First, the wave generation and propagation is investigated without any floater present. Then, the soft-moored semi-submersible is simulated in regular waves, with and without current, and the vessel motions and mean drift loads are analyzed. Finally, the CFD results are compared to results from potential flow based linear diffraction calculations, and to results from the wave basin. This study confirms that CFD is able to calculate the drift loads accurately in various regular waves. Furthermore, it can be observed that linear potential flow theory severely underpredicts the mean drift loads for steep waves with or without current.
Experimental Studies of Additive Manufacturing for Subsea Enclosures
Authors: Krohmann Sascha , Rautmann Louis Leon , Glatzer Lars , Kosleck Sascha 
Published: October 2022

Abstract
Additive manufacturing has become an essential part of rapid prototyping. In ocean engineering and especially ocean research technology, additive manufacturing can be an effective and cost-efficient way of creating highly customized products such as pressure-resistant enclosures with complex requirements. Furthermore, using lightweight 3D-printing materials significantly reduces the component’s weight. Conversely, payloads can be increased — another advantage compared to pressure enclosures built from conventional materials.
In this context, an experimental study of the behaviour of additive manufactured enclosures for subsea applications is performed. For this purpose, a suitable design is selected and adapted to meet manufacturing process requirements. Polyethylene terephthalate (PETG) and polycarbonate (PC) are selected as filament materials. In addition, post-printing treatments are studied. The various specimens are immersed in water to ensure a sufficient saturation level. After a period of three days, each sample is then exposed to increased hydrostatic pressure until collapse.
Finally, all experimental results are used to establish initial design and safety factors, reflecting the mechanical properties of the materials as well as the specific characteristics of the selected additive manufacturing process.
Vortex-Induced Vibrations of a Top-Tensioned Riser in Combined Currents and Waves
Authors: Yin Decao , Wu Jie , Lie Halvor , Passano Elizabeth , Sævik Svein , Grytoyr Guttorm , Tognarelli Michael A. , Andersen Torgrim , Igland Ragnar , Karunakaran Daniel , Gaskill Collin 
Published: October 2022

Abstract
Offshore drilling risers, top-tensioned risers and many production risers are top tensioned, connecting the vessel and seabed via joints. External loads such as currents, waves and vessel motions introduce cyclic loads and motions on riser sections, which may shorten the service life due to accumulated fatigue damage. Dynamic responses under combined currents and waves are more complicated than vortex-induced vibrations (VIV) due to pure currents, and it is not fully understood.
Several model test campaigns on top-tensioned riser (TTR) have been carried out at SINTEF Ocean (former MARINTEK) during the past decades. Currents, waves and vessel motions were modelled, and the riser model responses were measured. In this study, selected cases from such model tests are analysed, and used to validate a semi-empirical time domain VIV prediction tool — VIVANA-TD.
A better understanding of the dynamic responses of TTR under combined currents and waves has been achieved. By comparing the results from numerical simulation using VIVANA-TD and model test measurements, validity and limitation of the time domain tool have been investigated. Important features that need to be considered are discussed. The experience gained from the present study establishes a good basis for VIV and wave load prediction of full-scale TTRs under combined currents and waves where the uncertainty of VIV prediction is further reduced.
Ice-Induced Loads on Offshore Wind Turbines in the Baltic Sea
Authors: Tabri Kristjan , Tõns Tõnis , Suominen Mikko , Kõrgesaar Mihkel 
Published: October 2022

Abstract
The interaction of sea ice with offshore structures is an important engineering concern in ice-infested areas. This paper presents a procedure to evaluate ice loads acting at the sloping offshore wind turbines in the Estonian territorial waters at the Baltic Sea, where the waters are seasonally covered by ice. Region-specific characterization of ice thickness and ice days is done with the help of assessing ice maps from a period of 15 years. For each year, the number of days with ice coverage and thickness are determined. The extreme value probability distribution for annual maximum ice thickness is determined by fitting an asymptotic extreme value distribution to the maximum annual ice thickness.
For ice-structure interaction, a numerical ice model suitable for the Baltic Sea ice is implemented. The ice is treated as an isotropic, brittle material described by stress-strain curves for compression and tension. Numerical assessment is conducted to evaluate the ice load history, load maxima, and variations for a selected wind turbine foundation design.
High Frequency Tail in Measured Wave Spectra of Steep to Breaking Sea States
Authors: Scharnke Jule , Ewans Kevin , Kirezci Cagil , Babanin Alexander 
Published: October 2022

Abstract
A recent study investigated whether it is physically feasible to generate the tail of a JONSWAP wave spectrum in a basin, and what the influence of wave breaking is on the energy content of this high frequency tail. It has been observed in basin measurements at MARIN that in steep sea states a dip starts to develop in the high frequency tail of the spectrum. This dip occurs due to non-linear wave interactions and/or wave breaking and a resulting energy shift and dissipation. This effect cannot be compensated by adding more energy at the wave maker at these frequencies, as the energy will continue to shift/dissipate as more non-linear interaction and wave breaking occurs. The objective of this research was to investigate whether a similar energy dip would occur in real environments or whether the effect is related to the fact that in lab environments the waves are generated at one location of the basin and not through wind blowing over the sea surface continuously.
In cooperation with the University of Melbourne and MetOcean Research, several examples have been found in full scale measurements as well as non-linear wave simulations where a similar energy dip appears to occur. In this paper the physics involved in the reduced energy of the high frequency tail of very steep wave spectra are discussed and basin wave measurements are compared to nonlinear simulations and full scale measurements.
Performance of PA6C Plastic Sheaves Used for Mooring Line Installation
Authors: Hellum Vidar , Vaalandsmyr Anders , Schonlau Thomas , Heimdal Anette , Meijer Jawk 
Published: October 2022

Abstract
Mooring lines are important components in floating offshore energy installations such as wind turbines and oil and gas vessels. Efficient installation of the mooring lines is important to reduce costly and energy consuming offshore operations. In the present paper investigations have been performed on the performance of sheaves made from Lamigamid® 319, which is a specific type of PA6C plastic. The sheaves are intended for subsea pull-in operations of mooring lines during mooring line installation. The sheaves are a vital component of a proposed installation system which could limit the time spent on subsea operations. Additionally, the low density of the material, the possibility of using it without bearings and using highly stressed sheaves makes it possible to reduce the necessary material for temporary equipment to a minimum. Initial Finite Element Analyses based on material models from tension tests showed that the designed sheaves would suffer large deformations when subject to the design loads. A full-scale test was performed to corroborate these results but during this test almost no permanent deformation was recorded on the sheave. Further, a test series with compression tests of different shaped samples were initiated. The first results from this test series showed a remarkable strength of the material in compression and raised several questions regarding models for predicting the behavior of Lamigamid® 319 during loading. Hence, further tests were done and modelling techniques for finding structural capacity are discussed.
Experimental Investigation of Slamming Loads on Vertical Column Exposed to Short and Long Crested Waves
Authors: Økland Ole David , Lian Gunnar , Vestbøstad Tone 
Published: October 2022

Abstract
Model test campaigns conducted recent years indicate large wave impact loads on vertical surfaces above the waterline for various types of moored floating structures. These impacts are caused by breaking or near breaking waves in extreme sea states. Due to the large variability of the load, it is challenging to estimate the characteristic slamming loads, defined as the q-annual extreme 3-hour slamming load level of 10-2 for the Ultimate Limit State (ULS) and 10-4 for the Accidental Limit State (ALS). Hence, many tests realizations are necessary to assess extreme loads.
It is common practice to assume long crested waves in design against slamming loads. This assumption is regarded as conservative, and there have been indications that the effect of short crested waves on impact loads could be significant. In the present work an experimental investigation was set up to study effect of short crested waves for slamming against a rigid vertical column. Influence of current and other modeling parameters like type of wavemaker (single vs double flap), were also studied. A test model in scale 1:55 of a 31m diameter column at water depth 121m was used. The area of the column facing the incoming wave was instrumented by slamming panels. The setup covers 80 degrees of the cylinder circumference over a height of 24 meters from the still water surface and upwards. In addition to the slamming loads measured on the column, shear force and bending moment at the base of the column and global accelerations for the column were measured. High-speed video recordings were made for slamming events above a given threshold.
Modification of Double Bottom Height and Its Effect to the Ultimate Strength
Authors: Muis Alie Muhammad Zubair , Suci Indah Melati , Arafat Andi Muhammad Alfian , Juswan  , Mustafa Wahyuddin 
Published: October 2022

Abstract
Double bottom is one part of the ship’s construction which is located at the bottom and it functioned to overcome when the ship collides with the other object at the outer of ship’s bottom. One of the parameters of the double bottom that must be considered is double bottom height. These would affects to the section inertia, section modulus and neutral axis position leading to the ultimate strength of ship.
The objective of the present study is to analyze the ultimate strength caused by the double bottom height before and after modification. The double bottom height is analyzed according to the existing condition, national and international classification. Those formulas are different so that it is very important to know those effects. The numerical method is adopted to analyze the tankers ship caused by changing the double bottom height before and after modification. The force rotation is given at the master node since it is placed after determined the position of neutral axis as reference point.
It is observed that the double bottom height gives significant influence to the ultimate strength according to existing condition, national and international classification before and after modification under hogging and sagging conditions. The ultimate strength in terms of the moment-curvature relationship including their behavior is presented in this study.