bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of a Transient Model for Studying Kick Migration Velocities and Build-Up Pressures in a Closed Well
Authors: Ngoc Tat Thea Hang , Gomes Dalila , Fjelde Kjell Kåre 
Published: October 2021

Abstract
The objective of the paper is to show that using pressure build-up curves for estimating kick migration velocities can be unreliable. This will be demonstrated by using a transient flow model where different flow patterns including suspended gas are considered. Suspended gas will occur in Non-Newtonian drilling fluids. This can also be the reason why there is reported large discrepancies in literature about what the gas kick migration velocities can be.
A transient flow model based on the drift flux model supplemented with a gas slip relation will be used. The model will be solved by an explicit numerical scheme where numerical diffusion has been reduced. Different flow patterns are included i.e. suspended gas, bubble flow, slug flow and transition to one-phase gas. Kick migration in a closed well will be studied to study how pressure build-ups evolve. A sensitivity analysis will be performed varying kick sizes, suspension limits and changing the transition intervals between the flow patterns.
It is seen in literature that the slope of the pressure build-up for a migrating kick in a closed well has been used for estimating what the kick velocity is. It has been reported earlier that this can be an unreliable approach.
In the simulation study, it is clearly demonstrated that the suspension effect will have a significant impact of reducing the slopes of the pressure build-ups from the start of the kick onset. In some severe cases, the pressure builds up but then it reaches a stable pressure quite early. In these cases, the kick has stopped migrating in the well. However, in the cases where the kicks are still migrating, it seems that the bulk of the kick moves at the same velocity even though the degree of suspension is varied and gives different slopes for the pressure build-up. Hence, it seems impossible to deduce a unique gas velocity from different pressure build-up slopes. However, abrupt changes in the slope of the pressure build-up indicate flow pattern transitions.
The Impacts of Climate Change on the Windows of Offshore Operations
Authors: Acton Caroline 
Published: October 2021

Abstract
Ocean renewable energy has a central role to play in decarbonizing the global energy system. The emergence of new technologies such as floating wind farms will significantly increase offshore wind deployment by providing access to large areas of the seabed that are not suitable for fixed bottom turbines. Operations and Maintenance (O&M) is estimated to contribute 50% to an offshore wind farm’s total operational cost. The ability to improve the efficiency of O&M activities will enable offshore wind to compete with traditional fossil-based and onshore-renewable generation methods. To achieve this, an accurate characterization of the metocean environment is a mechanism of reducing delays and costs across the entire project lifecycle. One of the most significant costs associated with offshore operations is accessing a site with vessels. Site access is determined using vessels constraints in the maximum allowable meteorological and ocean (metocean) conditions and is defined as weather window analysis. However, industry guidelines and standards rely on historical data and do not consider the impact of climate change on the marine climate and the associated vessel operability. This requires the use of climate projection data. The opportunity to use an existing industry metric such as weather windows will tailor the climate projection data to the end-users needs. This paper’s findings suggest that climate change will alter the metocean environment and vessel operability for the case study location investigated. The findings demonstrate the value of site-specific assessment of the future wave climate to inform operational decision making. The main conclusion is that longer-term planning will require the offshore wind sector to consider the impact of climate change on O&M activities.
Underdeck Wave Slamming Model Tests for a Drilling Semi-Submersible Unit
Authors: Xu Lixin , Teng Xiaoqing , Wang Jinguang , Lee Sing-Kwan , Liu Jiancheng , Guo Yinghao , Xiao Longfei 
Published: October 2021

Abstract
Negative air gap and wave slamming load on the deck box of drilling semi-submersible units in severe storm have received a great deal of attention, due to the COSL Innovator accident in 2015. Equally important is vertical slamming load on the MODU underdeck, which is less reported in the literature. The present paper attempts to derive characteristic vertical slamming pressure on the deck bottom, based on an extensive model test program for a drilling semi-submersible unit, CM-SD1000.
A total of 96 3-hour wave impact tests were conducted including 4 sea states selected along the DNV steepness criterion curve in 3 wave headings. Two critical sea states were identified and each was tested with 16 random realizations in both the head and the beam waves. 8 force panels were installed on the under-deck to capture vertical wave impact events. It is found that the peak slamming pressures obtained can be fitted well with both Weibull and Gumbel probability function. The extreme vertical impact pressure predicted are of the same order of magnitude as the extreme horizontal impact pressure.
The present study also shows that rise velocities of the wave surface relative to the deck bottom have a remarkable correlation with the wave slamming pressure in terms of probability distribution. The relative rise velocities can be properly derived from wave probe measurements. This offers an alternative approach to estimate the vertical impact pressure without resort to force panels.
In contrast to horizontal wave slamming, the magnitude and frequency of vertical ones simply increases with significant wave height and wave steepness has much less effect. It is found that the extreme vertical impact pressure can be approximated well by a linear function of the significant wave height. The linear relationship, if validated by more tests, may help evaluate structural strength of the deck bottom before wave basin model testing.
Numerical Simulation of Model Test in Pre-Sawn Ice by CFD-DEM Coupled Method
Authors: Seo Dong Cheol , Wang Jungyong 
Published: October 2021

Abstract
Arctic shipping activities have been steadily increased due to global warming and economic benefit. As a result, there are more demands to estimate the ship performance in various ice conditions at the early design stage. In this paper, a CFD-DEM coupled approach was applied to estimate the ice resistance and broken ice behavior around the hull including hydrodynamic interactions. For the simulation, the moving ship in the stationary ice field was implemented using the overset grid technique. The estimated ice resistance as well as ice behaviors around the hull from the simulations were compared with model test results and underwater videos of the same vessel in a similar ice condition. The results demonstrated good agreement with model test measurements and further improvement for actual application was discussed in the paper.
Condition Monitoring of Ship Propulsion Systems: State-of-the-Art, Development Trend and Role of Digital Twin
Authors: Nejad Amir R. , Purcell Etienne , Valavi Mostafa , Hudak Roman , Lehmann Benjamin , Gutiérrez Guzmán Francisco , Behrendt Felix , Bõhm Angelo Mario , von Bock und Polach Franz , Nickerson Brendon M. , Bekker Anriëtte , Drazyk Withold 
Published: October 2021

Abstract
This paper describes the current implementations and development trends of condition monitoring as it pertains to ship propulsion systems. In terms of total incidents in the shipping industry in the last five years, failures relating to the propulsion system represent the majority. Condition monitoring offers effective early detection of failure which translates to increased reliability and decreased maintenance costs. Current industrial practices are often limited to performance monitoring rather than condition monitoring. Special focus is afforded to how condition monitoring is implemented on board ships, which regulatory codes are relevant and the summary of state-of-the-art research in marine machinery. Moreover, operation and monitoring in extreme environmental conditions, such as the Arctic and Antarctic with ice impact on the propulsion has been discussed. The new developments, in particular, digital twin approaches in health and condition monitoring have been highlighted, considering its pros and cons and potential challenges.
On the Role That the End Shape of an Underwater Vehicle Plays on Wave-Induced Heave Forces
Authors: Suriben Kristia M. , Klamo Joseph T. , Yeager Kathryn I. , Kwon Young W. 
Published: October 2021

Abstract
This paper investigates the error incurred by predicting the wave-induced heave forces on a submerged body using a mathematically simple flat face bow and stern rather than the typical curved ones. We examine both theoretically and experimentally how the heave force changes when flat end faces replace hemispheric end caps. We consider bodies with various length-to-diameter ratios to identify the influence that the ratio of the end cap length to the total body length plays on the heave forces. We also consider bodies with forward speed to identify if heave forces are affected by leading edge separation around the blunt front face which is not present for the hemispheric end cap. The theoretical predictions are from an existing potential flow analytical solution while the experimental results were collected in a towing tank with wavemaking capability. The theoretically predicted percent increase in the heave forces caused by the flat end face was confirmed by the experimental results. Finally, the theoretical predictions also showed that the percent increase in the heave force is independent of the forward speed of the body. This was also confirmed with the experimental results.
A Concept for Floating Offshore Wind Mooring System Integrity Management Based on Monitoring, Digital Twin and Control Technologies
Authors: Puras Trueba Alberto , Fernández Jonathan , Garrido-Mendoza Carlos A. , La Grotta Alessandro , Basurko Jon , Fonseca Nuno , Arrabi Iratxe , Savenije Feike , Pourmand Payam 
Published: October 2021

Abstract
Efficient operation of mooring systems is of paramount importance to reduce floating offshore wind (FOW) energy costs. MooringSense is an R&D project which explores digitization to enable the implementation of more efficient integrity management strategies (IMS) for FOW mooring systems. In this work, the MooringSense concept is presented. It includes the development of several enablers such as a mooring system digital twin, a smart motion sensor, a structural health monitoring (SHM) system and control strategies at the individual turbine and farm levels. The core of the digital twin (DT) is a high-fidelity fully coupled numerical model which integrates simulation tools to allow predictive operation and maintenance (O&M). Relevant parameters of the coupled model are updated as physical properties evolve due to damages or degradation. The DT assimilates information coming from the physical asset and environmental sensors. Besides, a smart motion sensor provides feedback of the attitude, position, and velocity of the floater to allow the computation of virtual loads in the mooring lines, the detection of damages by the SHM system and the implementation of closed-loop control strategies. Finally, the IMS takes advantage of the mooring system updated condition information to optimize O&M, reduce costs and increase energy production.
A Numerical Study of the Hydrodynamics of an Offshore Fish Farm Using REEF3D
Authors: Wang Gang , Martin Tobias , Huang Liuyi , Bihs Hans 
Published: October 2021

Abstract
In this paper, the CFD framework REEF3D is utilized to investigate the hydrodynamics of a large offshore fish farm in waves. The solver consists of a rigid body dynamics solver for the frame structure coupled to a fluid solver including the shielding effects of the nets. The solver and the grid independence are validated using a 2D numerical wave tank, a free decay test, and a study of the wave loads on a rigid net panel. Then, the effects of regular wave parameters, the thickness of the vertical outer columns of the structure, and varies aspect ratios on the loads, response and maximum mooring tensions are investigated. It is concluded that the response is sensitive to the wave period rather than the wave height and that the net system accounts for about 30% of the total drag but does not influence the structural response to a larger extend. The effect of the aspect ratio on the hydrodynamics is more distinct than that of the frame thickness especially. Thus, the first step towards a systemic evaluation of the importance of different structural parts of an offshore fish cage for the expected responses is presented in this paper.
Numerical Simulation of Wave Interaction With a Pair of Fixed Large Tandem Cylinders Subjected to Regular, Non-Breaking Waves
Authors: Mohseni M. , Guedes Soares C. 
Published: October 2021

Abstract
The wave interaction with cylinders placed in proximity results in significant modification of the wave field, wave-induced processes, and wave loading. The evaluation of such a complex wave regime and accurate assessment of the wave loading requires an efficient and accurate numerical model. Concerning the wave scattering types identified by Swan et al. (2015) and lateral progressive edge waves, this paper presents the application of a two-phase Computational Fluid Dynamics (CFD) model to carry out a detailed investigation of nonlinear wave field surrounding a pair of columns placed in the tandem arrangement in the direction of wave propagation and corresponding harmonics. The numerical analysis is conducted using the Unsteady Reynolds-Averaged Navier-Stokes/VOF model based on the OpenFOAM framework combined with the olaFlow toolbox for wave generation/absorption. For the simulations, the truncated cylinders are assumed vertical and surface piercing with a circular cross-section subjected to regular, non-breaking fifth-order Stokes waves propagating with moderate steepness in deep water. Primarily, the numerical model is validated with experimental data provided by ITTC (OEC)[1] for a single cylinder. Future, the given simulations are conducted for different centre-to-centre distances between the tandem large cylinders. The results show the evolution of a strong wave diffraction pattern and consequently high wave amplification harmonics around cylinders are apparent.
Tank Test and Numerical Simulation of Spar Type Floating OTEC
Authors: Hirao Shunka C. , Umeda Jun , Kokubun Kentaroh , Fujiwara Toshifumi 
Published: October 2021

Abstract
National Maritime Research Institute, NMRI, had been studying the analytical method on safety assessments of floating power generation facilities for ten years more. As a part of these studies, an Ocean Thermal Energy Conversion (OTEC) was also studied in our institute.
The OTEC normally has a very long and thick Cold-Water Pipe (CWP) with an unanchored end to pump up a large amount of cold-water continuously. From the viewpoints of the safety assessments of the OTEC operation, it is noteworthy to confirm the effect of the existing long pipe against a floating unit/body and an effect of internal flowing water. It is necessary, moreover, to consider the Vortex Induced Vibration (VIV) effect for floater motions and structural analysis of the pipe itself and a connecting point of the floating structure.
In this paper, the results of model tests and numerical simulations of a spar type floating OTEC with a single CWP in waves and currents are presented. The CWP model was made of material fitting the scaling law for a planned full scale OTEC. The specific and unique phenomena of the floating OTEC were confirmed from the model test results. Based on the results of the tank tests and the numerical simulations, we confirmed the necessary items and arrangements for safety evaluations. In detail, the internal flow increased the bending moment at the connection point.
Simplified Formulation of Coupled System Between Moored Ship and Elastic Pipe for OTEC Plantship
Authors: Hisamatsu Ryoya , Utsunomiya Tomoaki 
Published: October 2021

Abstract
A commercial-scale Ocean Thermal Energy Conversion (OTEC) floating platform will require a large diameter Cold Water Pipe (CWP) to be attached. Several studies have analyzed the dynamic behavior of the coupled system between the floating platform and the CWP. However, the characteristic of the coupled behavior has not yet been fully understood. This study aims to formulate the coupled system of an OTEC floating plant and simplify the formula to clarify the characteristic of the coupled behavior. The formula is suitable for validation of the numerical simulation results and the preliminary design of an OTEC plant. In the first section of this paper, we derive the equation of motion and equilibrium of the direct moored floating body and an elastic pipe hanged off from the floating body. In the second section, we verify the formula for a 100MW OTEC plantship with 800m length and 12m diameter CWP. The Response Amplitude Operator (RAO) is calculated by solving the equation of motion and statistics responses in 3 hours are compared with a numerical simulation by OrcaFlex. As the result of the comparison, we observed that the present formula is applicable in the early stage of the practical design loop.
Development and Implementation of an Arctic Sea Route Search System
Authors: Sugimura Takeshi , Yamaguchi Hajime , Yabuki Hironori 
Published: October 2021

Abstract
With the reduction in extent of Arctic Ocean sea ice in recent years, commercial use of Arctic Sea shipping routes has attracted increasing attention. An urgent task for promoting the use of safe and cost-efficient routes in the Arctic Sea is the construction of a navigation support system. Such a system is essential not only for monitoring and forecasting the extent of sea ice but also for integrating such information in determination of the optimal route. This research developed an Arctic Sea Route Search System that has been published as a web application on the Arctic Data archive System website. Ship speed is calculated based on an approximate expression of actual Automatic Identification System data and an Ice Index, which is an index that reflects the ease of navigation based on ice type and the ship’s ice class. The A* algorithm searches for the optimal route using a search graph that places nodes at the grid positions of input data. Comparison of several test calculations using different parameters confirmed that the route search system provides reasonable results.
Efficient Calculation of Spatial and Temporal Evolution of Hydrodynamic Loads on Offshore Wind Substructures
Authors: Pakozdi Csaba , Kamath Arun , Wang Weizhi , Martin Tobias , Bihs Hans 
Published: October 2021

Abstract
Estimation of the hydrodynamic loads based on strip theory with the Morrison equation provides a fast and inexpensive method for load estimation for the offshore industry. The advantage of this approach is that it requires only the undisturbed wave kinematics along with inertia and viscous force coefficients. Over the recent years, the development in numerical wave tank simulations makes it possible to simulate nonlinear three-hour sea states, with computational times in the order of real time. This provides an opportunity to calculate loads using wave spectrum input in numerical simulations at reasonable computational time and effort. In the current paper, the open-source fully nonlinear potential flow model REEF3D::FNPF is employed for the wave propagation calculations. Here, the Laplace equation for the velocity potential is solved on a sigma-coordinate mesh with the nonlinear free surface boundary conditions to close the system. A technique to calculate the total acceleration on the sigma-coordinate grid is introduced which makes it possible to apply strip theory in a moving grid framework. With the combination of strip theory and three-hour wave simulations, a unique possibility to estimate the hydrodynamic loads in real time for all discrete positions in space within the domain of the numerical wave tank is presented in this paper. The numerical results for inline forces on an offshore wind mono-pile substructure are compared with measurements, and the new approach shows good agreement.
Validation of Forced Heave Simulations on a Planing Hull
Authors: Husser Nicholas , Judge Carolyn , Brizzolara Stefano 
Published: October 2021

Abstract
Advances in nonlinear modeling techniques have created opportunities for more robust modeling of planing hull dynamics than previous techniques relying on linear assumptions. These techniques rely on the imposition of complex, coupled forced motions on a hull. RANSE CFD provides a distinct advantage over experimentation when imposing complicated forced motions because mechanical limitations of the forced motion mechanism and uncertainty in the prescribed motion are eliminated, though the accuracy of the simulations needs to be validated. In this work, a series of sinusoidal forced heave experiments on a planing craft are used to validate the force response predicted by simulation for the same forced motion. The accuracy of the predicted force response is evaluated relative to the experiments with the experimental setup uncertainty considered. Within the experimental setup uncertainty, the force response is predicted well by RANSE CFD and is found to be reasonably accurate. The dynamic trim angle is found to have a major impact on the dynamic force response with variations on the order of half a degree having substantial impacts on the measured forces.
Experimental Investigation of Large Particle Slurry Transport in Vertically Oscillating Pipe for Subsea Mining
Authors: Masanobu Sotaro , Takano Satoru , Kanada Shigeo , Ono Masao 
Published: October 2021

Abstract
For subsea mining, it is important to predict the pressure loss in oscillating pipes for the safe and reliable operation of ore lifting as well as the design of lifting system. In the present paper, the authors focused on the internal flow in vertical lifting pipe oscillating in the axial direction and carried out slurry transport experiment to investigate the effects of pipe oscillation on the pressure loss. The spherical alumina beads and glass beads were used as the solid particles in the experiment, and the oscillating periods and amplitudes of pipe model as well as the solid concentrations and the mean slurry velocities were varied. The time-averaged components of hydraulic gradient calculated by the prediction method for the steady flow proposed in the past by the authors agreed well with the experimental ones. As for the fluctuating components of hydraulic gradient, the calculation results using a homogeneous mixture model were compared with the experimental data. The comparison result indicated that the homogeneous mixture model would be applicable to the prediction of pressure loss in the vertical pipe oscillating in the axial direction.