bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laboratory Experiment of Two-Degree-of-Freedom Vortex-Induced Vibrations of Circular Cylinder in Regular Waves
Authors: Opinel Pierre-Adrien , Srinil Narakorn 
Published: December 2020

Abstract
This paper presents new laboratory experiments of two-degree-of-freedom vortex-induced vibration of a flexibly mounted vertical circular cylinder in regular waves. A new experimental model has been developed and tested in the Wind, Wave & Current Tank at Newcastle University. The system mass ratio is close to 3 and the cylinder aspect ratio based on its submerged length is close to 27. The Stokes first-order wave theory is considered to describe the depth-dependent, horizontal velocity amplitude of the wave flow in the circulating water tank. This wave theory is satisfactorily validated by the wave probe measurement. The effects of cylinder stiffness affecting system natural frequencies are also investigated by using a combination of different spring setups in in-line and cross-flow directions. For each set of springs, VIV tests are performed in regular waves, with flow frequency ranging from 0.4 to 1 Hz and amplitude from 0.01 to 0.09 m. The associated Reynolds number at the water surface is in a range of 1.7 × 103–1.5 × 104. The surface Keulegan-Carpenter number (KC) is in the range of 2 &lt; KC &lt; 28 while the surface reduced velocity (Vr) is in the range of 0.5 &lt; Vr &lt; 16 depending on the implemented spring stiffness. Combined in-line/cross-flow oscillations of the cylinder are measured using two non-intrusive Qualisys cameras and the associated data acquisition system. The spring forces are also acquired using four load cells. Results reveal that, depending on KC and Vr, the cylinder primarily oscillates at the flow frequency in the in-line direction and at an integer (mainly 2, 3 and 4) multiple of the flow frequency in the cross-flow direction. Such occurrence of multi frequencies corroborates other experimental and numerical results in the literature. Several peculiar trajectories are observed, including infinity, butterfly, S and V shapes. The present experimental data of vibration amplitudes and oscillation frequencies in in-line/cross-flow directions as well as response patterns provide new results and improved understanding of VIV in oscillatory flows. These will be useful for the development of an industrial tool in predicting offshore structural responses in waves.
Future Scenarios for Arctic Shipping
Authors: Bergström Martin , Leira Bernt J. , Kujala Pentti 
Published: December 2020

Abstract
Maritime activity in the Arctic is on the increase, driven by multiple factors including the development of Arctic natural resources, climate change, regulatory changes, improved technology and operations, national and international policies, infrastructure developments, fuel prices, and the global economy. This article aims to identify and analyze such change drivers and to discuss how these might influence the future of three specific segments of Arctic shipping: destination-Arctic shipping (operation between Arctic and non-Arctic locations), trans-Arctic shipping (operation between non-Arctic locations through Arctic waters), and Arctic cruising. The study finds that each considered segment of Arctic shipping is subject to a unique set of significant change drivers.
Cemented Wellbore Experiments Reveals That Cement Interface Debonding Modeling Overestimate Potential Leakage Rates
Authors: Speer Zachary , Wise Jarrett , Nygaard Runar , Hareland Geir , Ford Eric , Arild Øystein , Lohne Hans Petter , Kragset Steinar 
Published: December 2020

Abstract
Leakage pathways may develop in wellbores during construction, production, or during and after plug and abandonment (P&A). These pathways are created due to events and conditions during cementing operations, or because of physical and chemical changes after cementing such as changes in temperature and wellbore pressures, and deterioration of the cement. Common leakage pathways develop inside the cement sheath, or as microannuli along the cement-tubing interface. Numerous evidence exists showing that wellbores leak, but there is no verified method to determine if a well will leak or not. To ensure long term wellbore integrity, leakage risks need to be evaluated for plugged and abandoned wells.
To evaluate leakage risks from plugged and abandoned wells, numerical finite element models have been developed and used to investigate leakage scenarios during the life of the well. Currently, little work has been done to verify finite element numerical models with experimental data regarding flowpath size in cement sheaths. The aim of this paper is to model previously published experimental data to determine if the finite element models can accurately predict leakage potentials.
Two lengths of cemented annuli were modeled, each with conventional and expanding cement to replicate the Aas et. al. [1] experiments. The numerical results show that the simulated microannuli overestimate flow rate compared to experimental data, indicating that flow path dimensions and/or fluid friction factor does not accurately represent the fluid flow in the experiments.
Wave Propagation in Continuous Sea Ice: An Experimental Perspective
Authors: Passerotti Giulio , Alberello Alberto , Dolatshah Azam , Bennetts Luke , Puolakka Otto , von Bock und Polach Franz , Klein Marco , Hartmann Moritz , Monbaliu Jaak , Toffoli Alessandro 
Published: December 2020

Abstract
Ocean waves penetrate hundreds of kilometres into the ice-covered ocean. Waves fracture the level ice into small floes, herd floes, introduce warm water and overwash the floes, accelerating ice melt and causing collisions, which concurrently erodes the floes and influences the large-scale deformation. Concomitantly, interactions between waves and the sea ice cause wave energy to reduce with distance travelled into the ice cover, attenuating wave driven effects. Here a pilot experiment in the ice tank at Aalto University (Finland) is presented to discuss how the properties of irregular small amplitude (linear) waves change as they propagate through continuous model sea ice. Irregular waves with a JONSWAP spectral shape were mechanically generated with a very low initial wave steepness to avoid ice break up and maintain a consistent continuous ice cover throughout the experiments. Observations show an exponential attenuation of wave energy with distance. High frequency components attenuated more rapidly than the low frequency counterparts, in agreement with a frequency-cubed power-law. The more effective attenuation in the high frequency range induced a substantial downshift of the spectral peak, stretching the dominant wave component as it propagates in ice.
Study on Ship Operational Effect for Defining Design Values on Ship Motion and Loads in North Atlantic
Authors: Miratsu Rei , Fukui Tsutomu , Matsumoto Toshiyuki , Zhu Tingyao 
Published: December 2020

Abstract
Ships are being operated under consideration of the safety for lives and properties, economical reasons and so on, therefore the sea states in natural phenomena and those actually encountered by ships are thought to be different, and the latter includes some effects of human operational factors (so called “ship operational effect”). Quantitative evaluation of the ship operational effect is important to consider rational wave design loads for the evaluation of hull structure strength.
The purpose of this study is to evaluate the ship operational effect in actually encountered sea states quantitatively for defining design values on ship motion and loads.
In this study, the quantitative evaluation of ship operational effect is carried out considering the wave heights and wave periods in the North Atlantic. It was confirmed from the results that the quantitative ship operation effects vary depending on the hindcast wave source. Furthermore, the ship speeds tend to decrease in head, bow and beam seas when the encountered significant wave heights became higher. Moreover some patterns are observed on the typical encountered wave headings in the North Atlantic, which comes from the combination of the features of the North Atlantic routes and the wave propagation directions of the natural phenomena.
On the Effect of Non-Linear Boundary Conditions on the Wave Disturbance and Hydrodynamic Forces of Underwater Vehicles Travelling Near the Free-Surface
Authors: Lambert William , Brizzolara Stefano 
Published: December 2020

Abstract
This study compares the effect of non-linear free-surface boundary conditions for a high-order non-linear free-surface Rankine-source boundary element method on wave disturbance and hydrodynamic forces acting on an underwater vehicle travelling near a calm free-surface. In particular, simulations for a steady nonaxisymmetric prolate spheroid using different basis flows and linearization techniques were compared to an analytical method achieved by Chatjigeorgiou using a multipole expansion of Green’s functions. It appears that at low Froude numbers, the basis flow used in the formulation contributes significantly to differences in the steady solutions for wave resistance and pitch, whereas for higher Froude numbers the linearization technique becomes a more defining feature. Upon observation of the analytical solution for wave resistance, one can see that it was formed under a Neumann-Kelvin formulation and this is supported by the Neumann-Kelvin simulations converging well to the analytical solution.
Further comparisons were made using a wave directional energy spectrum gathered from transverse wave cuts of the free wave pattern. The spectral analysis allows for a higher level of comparison between all of the different cases, establishing a direct relation between the change in wave resistance and the energy content variation of the particular wave spectrum components.
A Non Linear Finite Element Model to Analyse the Dynamics of Subsea Lifting Operation Using Synthetic Cables
Authors: Carobino Evandro Souto , Pavanello Renato , Tommasini Rodrigo Batista , Fonseca Debora Junqueira , de Oliveira Carvalho Leonardo 
Published: December 2020

Abstract
In the context of subsea lifting many equipment and strategies are employed in order to avoid dynamic instabilities and complex mechanical behaviors during the installation procedures. One of those strategies is the use of synthetic cables to reduce the total sustained weight on the crane and to shift the resonance frequency of the system, leading to reductions of fails risks. This work presents a numerical model intended to predict the dynamic behavior of a cable-equipment system under the influence of the sea waves. The cable is discretized in a finite element mesh which accounts for a nonlinear material model for the elasticity of the cable. The nonlinear elastic law uses a polynomial function to represent the force on the cable as a function of the strain, being able to predict the variation of the stiffness for different load conditions. Further, hydrodynamic forces are considered acting on the equipment and are modeled via Morison’s equation, which introduces a quadratic nonlinear forcing term. The equation of motion is then integrated at the time domain through a Newmark-β predictor-corrector method in order to obtain the dynamic response of the system. Furthermore, an Orcaflex model is constructed using an equivalent linear stiffness representation for the synthetic cable. The results obtained are compared, and the differences between them are highlighted for typical subsea lifting scenarios. In this case, the proposed model can predict non trivial dynamic behaviors of the system such as dependence on the amplitude of the displacement of the lifting point. It is also presented the scenarios where the equivalent linear model is accurate in comparison to the nonlinear one and how the selection of the strain point used to linearize the model affects the dynamics of the system.
Numerical Simulations and Sea Trial for Leader Follower Formation Control of Cruising-Type AUVs
Authors: Umeda Jun , Kim Kangsoo , Sato Takumi , Inaba Shogo , Fujiwara Toshifumi 
Published: December 2020

Abstract
With the emphasis on the utilization of rich materials in the seabed in recent years, autonomous underwater vehicles (AUVs) are valued for technology to explore the oceans. Simultaneous operations of multiple-AUVs enable to investigate a wider area in a shorter time than the use of only a single AUV. During the survey, each AUV corrects the position error due to the inertial navigation system by the acoustic communication systems. All AUVs are required to be within the acoustic-communication available area. The formation control which can keep the desired relative positions becomes the mandatory function to explore the oceans efficiently while being within the acoustic-communication available area. In this study, a simple formation control-law based on a leader-follower algorithm was developed and validated through numerical simulations and sea trials. In the numerical simulations, waypoint tracking control-law and the proposed method were applied to the cruising-type AUVs and these control performances are compared. Sea trials using two cruising-type AUVs were carried out to evaluate the performance of the control-law.
Experimental Study on Three Phase Flow in Inclined Pipe for Deep Sea Mining
Authors: Takano Satoru , Masanobu Sotaro , Yamamoto Joji , Kanada Shigeo , Ono Masao , Sasagawa Hiroki 
Published: December 2020

Abstract
Subsea minerals exist in the deep water within Japanese exclusive economic zone. However, the development of subsea minerals is not commercialized. The Air-lift pump is the promising method for subsea minerals transport. It is significant to estimate the amount of lifting ore when the conditions of submergence ratio and supplying air volume are changed. The estimation of the amount of lifting ore needs the void fraction in three phase flow and friction loss in pipe. Therefore, the empirical methods to estimate the void fraction and friction loss in mainly vertical pipe were proposed in the previous studies. However, the lifting system for subsea minerals has not only vertical pipe but inclined pipe. There are few works for flow assurance on three phase flow in inclined pipe. Then we conducted the scale model experiment to investigate void fraction and friction loss. The experiment was conducted in the conditions of the five kinds of inclination angles. We used the glass beads as solid particles in the experiment. The glass beads were 4mm in diameter and 2553kg/m3 in density. The internal diameter of pipe was 26mm. We applied the empirical method for vertical or horizontal pipe proposed in previous researches to the present experimental condition. Then we compared the experimental results with the calculated ones on void fraction and friction loss. As the results, the calculated results were in good agreement with the experimental ones. Therefore, it was suggested that the void fraction and friction loss in the inclined pipe could be calculated by the empirical method based on the experiment on the vertical or horizontal pipe.
Feasibility Study on Fabrication of Large-Scale Offshore Structural Steel Component Using LAAM Technology
Authors: Chew Y. X. , Ang J. H. , Sastry K. Y. , Xu D. Q. , Kuik S. , Bi G. J. 
Published: December 2020

Abstract
ASTM A131 Steel, grade EH36 is a high strength steel used extensively as structural parts in shipbuilding, Oil and Gas applications. In this work, additive manufacturing of a support node connecting the main platform and columns for semi-submersible offshore vessel was performed using Laser Aided Additive Manufacturing (LAAM) process to evaluate both technical feasibility and economic viability. Both coupon and component levels LAAM process study was carried out. Properties of printed EH36 steel are significantly determined by the printing process parameters. EH36 deposited with optimized LAAM process has shown better mechanical properties than conventional rolled EH36 material. A deposition strategy was developed to distribute the accumulated residual stress, to minimize substrate distortion and stress-induced cracking in the print part. A hybrid approach combining both substrate and AM, with a 60% print to hot-rolled substrate plate weight fraction was proposed to enable printability and to enhance efficiency. Near-net-shape node was printed without cracking/delamination using optimized printing strategy. Total printing weight is 70kg and total time spent is 90 hours. It was concluded that LAAM technology is feasible for fabrication of large load bearing structural steel sections.
Simulating High Mode Vortex Induced Vibration of Riser in Linear Sheared Current Using an Empirical Time Domain Model
Authors: Kim Sang Woo , Sævik Svein , Wu Jie 
Published: December 2020

Abstract
This paper addresses the performance evaluation of an empirical time domain Vortex Induced Vibrations (VIV) model which has been developed for several years at NTNU. Unlike the frequency domain which is the existing VIV analysis method, the time domain model introduces new vortex shedding force terms to the well known Morison equation. The extra load terms are based on the relative velocity, a synchronization model and additional empirical coefficients that describe the hydrodynamic forces due to cross-flow (CF) and In-line (IL) vortex shedding. These hydrodynamic coefficients have been tuned to fit experimental data and by considering the results from the one of existing frequency domain VIV programs, VIVANA, which is widely used for industrial design.
The feature of the time domain model is that it enables to include the structural non-linearity, such as variable tension, and time-varying flow. The robustness of the new model’s features has been validated by comparing the test results in previous researches. However, the riser used in experiments has a relatively small length/diameter (L/D) ratio. It implies that there is a need for more validation to make it applicable to real riser design.
In this study, the time domain VIV model is applied to perform correlation studies against the Hanøytangen experiment data for the case of linear sheared current at a large L/D ratio. The main comparison has been made with respect to the maximum fatigue damage and dominating frequency for each test condition. The results show the time domain model showed reasonable accuracy with respect to the experimental and VIVANA. The discrepancy with regard to experiment results needs to be further studied with a non-linear structural model.
Casing Wear Simulation by Application of Real-Time Data and Predictive Modelling
Authors: Teigland Andreas , Sangesland Sigbjørn , Dale Stein Inge 
Published: December 2020

Abstract
Casing wear poses a significant safety hazard during drilling and production of hydrocarbons. Failure to maintain integrity due to inaccurate casing wear estimation can cause severe accidents or preclude prospective operations. Current industry practice is to estimate casing wear during the planning phase of the well and subsequently use assumed operational parameters with inherent uncertainties. This paper aims to study how to utilize real-time data to improve the industry standard methodology and evaluate the benefit of the modification. The research was conducted by applying the model on data from a well on the Norwegian continental shelf. There were two main objectives of the research.
Firstly, the industry standard approach to casing wear estimation was expanded to include real-time data. Application of real-time data to the industry standard method for estimating casing wear caused a significant difference in results. The approach using real-time data resulted in an estimate of more casing wear compared to the standard approach. Secondly, an algorithm for continuous prediction of casing wear at the end of operation was developed. The predictive algorithm resulted in consistently more accurate estimates in relation to the final value throughout the operation.
With variations in input parameters and consecutive casing wear of this magnitude, well integrity cannot be ensured during operation without application of real-time data. The failure to maintain well integrity demonstrates the necessity of the proposed approach.
Planning and Design of Floating Offshore Architecture
Authors: Takahashi Akane , Yoshida Ikuo 
Published: December 2020

Abstract
Floating offshore structures are attracting increasing attention as a method for addressing problems such as rising sea levels due to global warming and the increasing global populations. However, unlike ground structures, floating offshore structures must consider the effects of waves. The movement characteristics of the floating offshore structure have been reported. However, no studies have compared variations in motion response characteristics according to the scale of floating structures or buildings atop them, so it is currently difficult during the initial planning and design stages to estimate the size of superstructures that can be designed for a given marine area. Therefore, with the aim of obtaining basic data for planning floating offshore structures, in this study we developed floating structure modules (a square 36m on a side) according to their superstructure and investigated the basic motion response characteristics for each. We furthermore derived tendencies for horizontal acceleration and inclination occurring in individual modules according to design waves for Tokyo Bay.
1300 Tons Grouted Integrity Support Installation Case Study
Authors: Alonso Castro Beatriz , Daly Roland , Becerro Francisco Javier , Vabø Petter 
Published: December 2020

Abstract
The North sea Yme oil field was discovered in 1987, production started in 1996 and ceased after 6 years when it was considered no longer profitable to operate. In 2007 a new development was approved, being Yme the first field re-opened in the Norwegian Continental Shelf. The concept selected was a MOPUStor: comprising a jack-up unit grouted to a subsea storage tank. Due to compromised structural integrity and lack of regulatory compliance that came to light shortly after installation, the platform was required to be removed [1]. The remaining riser caisson and the future 1050 t wellhead module required a support to allow the re-use of the facilities and tap the remaining oil reserves. The innovative tubular frame support was designed as a braced unit, secured to the existing MOPUstor leg receptacles and holding a grouted clamp larger than typical offshore clamps for which design guidance in ISO is available. The existing facilities had to be modified to receive the new structure and to guide it in place within the small clearances available.
The aim of this paper is to describe the solutions developed to prepare and verify the substructure for installation; to predict the dynamic behavior of a subsea heavy lift operation with small clearances around existing assets (down to 150 mm); and to place large volume high strength grouted connections, exceeding the height and thickness values from any project ever done before. In order to avoid early age degradation of the grout, a 1 mm maximum relative movement requirement was the operation design philosophy. A reliable system to stabilize the caisson, which displacements were up to 150 mm, was developed to meet the criteria during grouting and curing. In the stabilizer system design, as well as the plan for contingencies with divers to restart grouting in the event of a breakdown, the lessons learned from latest wind turbine industry practices and from the first attempt to re-develop the field using grouted connections were incorporated. Currently the substructure is secured to provide the long term integrity of the structure the next 20 years of future production in the North Sea environment.