bluuebunny/crossref_metadata_2025_split huggingface dataset:
Load-Carrying Characteristics of Foam Core and Joint Geometry in Sandwich Structures
Authors: Ringsberg Jonas W. 
Published: December 2020

Abstract
Composite sandwich ships have laminated joints that contribute to a significant part of the ship’s weight. Their construction requires an extensive number of man-hours. There is great potential for weight and production-time-reduction through alternative joint designs. According to class rules, one is not allowed to benefit from the load-carrying capability of the core, i.e. the strength characteristics of the core shall be disregarded and geometry at the joint location is disregarded as well. The objective of the current investigation was to investigate the possibility of constructing a joint where the load-carrying capability of the foam core is accounted for, leading to a reduction in weight and production time. One specific joint in a 23 m composite sandwich catamaran was selected for study — a side wall-wet deck T-joint. This joint is considered to be crucial for the structural integrity of the current vessel. A global finite element (FE) model of the catamaran was designed and analysed in ANSYS. The loads and boundary conditions were applied to the global model according to DNV GL’s HSLC rules. Two local FE models of the joints (2D and 3D) were utilized for a parametric analysis with respect to structure response (stress concentrations and compliance with failure and fracture criteria). Finally, the results and conclusions from the study show the possibilities and advantages of incorporating the foam core material as a load-carrying member in joint design without compromising safety.
3D SPH Simulation of Wave Interaction Between Wave Energy Converters: Towards Optimum Wave Power Absorption in Wave Farms
Authors: Sasikala N. , Sannasiraj S. A. , Manasseh Richard 
Published: December 2020

Abstract
Ocean waves are one of the sustainable resources of renewable energy for carbon-free electricity. For cost-effective commercial-scale projects, Wave Energy Converters (WECs) are deployed in arrays with optimum spacing as an alternative for a large (oscillatory) device in isolation. It has been found that when the wave excitation frequency is close to the resonant frequency of the WEC, the efficiency factor of energy farms, called q-factor, increases with the oscillation amplitude of the device. It has been found that the maximum absorbed energy of WECs depends directly on array configuration as that the radiated and incident wave fields interfere to direct the energy flux in the ocean towards the floating bodies. In this paper, the fully nonlinear interaction between two 3D floating bodies in close proximity and excited near its’ resonance is studied using Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH). Apart from the calculations of q factor, hydrodynamic forces acting on the floating bodies and their dynamic responses are also calculated. An optimum array of WECs is proposed.
Design Considerations of a Subsea Shuttle Tanker System for Liquid Carbon Dioxide Transportation
Authors: Xing Yihan , Ong Muk Chen , Hemmingsen Tor , Ellingsen Kjell Einar , Reinås Lorents 
Published: December 2020

Abstract
Subsea pipelines and umbilicals are used for the transportation of fluids and electrical power between subsea installations and floating production systems (FPUs). The installation and maintenance of these systems can be expensive. In a conventional subsea field development, the produced fluids can be transported from the well to a FPU where they can be offloaded to a tanker (surface ship). In the case of carbon dioxide (CO2) injection into the well, the direction of flow is reversed, i.e., CO2 flows from the tanker to the FPU, down the riser base and through the subsea pipelines to the well. This offloading process is weather-dependent and cannot be performed in severe weather conditions, i.e., strong winds and large waves. This paper presents a novel subsea shuttle tanker system proposed by Equinor ASA designed to be a possible alternative to subsea pipelines, umbilicals and tanker ships. The subsea shuttle is intended to operate submerged under the sea surface to transport liquid CO2 from an existing offshore/land facility where CO2 is captured to a subsea well where the CO2 is injected into the reservoir. As the shuttle is subsea, it can operate under any type of weather conditions. Even though the subsea shuttle is proposed as a vehicle for liquid CO2 transport, it can also transport other types of cargo such as hydrocarbons, injection fluids, electrical power or subsea tools. The paper will discuss the most important design considerations surrounding the subsea shuttle tanker.
Numerical Analysis of Aeroelastic Responses of Wind Turbine Under Uniform Inflow
Authors: Huang Yang , Wan Decheng 
Published: December 2020

Abstract
With wind turbine blades becoming longer and slender, the influence of structural deformation on the aerodynamic performance of wind turbine cannot be ignored. In the present work, the actuator line technique that simplifies the wind turbine blades into virtual actual lines is utilized to simulate the aerodynamic responses of wind turbine and capture downstream wake characteristics. Moreover, the structural model based on a two-node, four degree-of-freedom (DOF) beam element is adopted for the deformation calculation of the wind turbine blades. By combing the actuator line technique and linear finite element theory, the aeroelastic simulations for the wind turbine blades can be achieved. The aeroelastic responses of NREL-5MW wind turbine under uniform wind inflow condition with different wind speeds are investigated. The aerodynamic loads, turbine wake field, blade tip deformations and blade root bending moments are analyzed to explore the influence of blade structural responses on the performance of the wind turbine. It is found that the power output of the wind turbine decreases when the blade deformation is taken into account. Significant asymmetrical phenomenon of the wake velocity is captured due to the deformation of the wind turbine blades.
Numerical Study of Yawed Wind Turbine Under Unstable Atmospheric Boundary Layer Flows
Authors: Wei Dezhi , Wan Decheng 
Published: December 2020

Abstract
Turbine-wake interactions among wind turbine array significantly affect the efficiency of wind farms. Yaw angle control is one of the potential ways to increase the total power generation of wind plants, but the sensitivity of such control strategy to atmospheric stability is rarely studied. In the present work, large-eddy simulation of a two-turbine configuration under convective atmospheric boundary layer is performed, with different yaw angles for the front one, the effect of turbine induced forces on the flow field is modeled by actuator line. Emphasis is placed on wake characteristics and aerodynamic performance. Simulation results reveal that atmospheric stability has a considerable impact on the behavior of wind turbine, wake deflection on the horizontal hub height plane for yawed wind turbine is relatively small, compared with the result of the empirical wake model proposed for wind turbine operating in the neutral stratification, which is attributed to the higher ambient turbulence intensity and large variance of wind direction in the convective condition. And associated with the smaller wake deflection, the total power production does not increase as expected when yawing the upstream turbine. In addition, due to the existence of great quantities of disorganized coherent turbulent structures in the unstable condition, the yaw bearing moment experienced by the downstream wind turbine increases dramatically, even if the rotor plane of the first turbine is perpendicular to the inflow direction.
Research on Real-Time Calculation Method of Load Response in FPSO Soft Yoke Mooring System Based on Long and Short-Term Memory Network
Authors: Sun Yu , Sun Liping , Li Peng , Ma Gang 
Published: December 2020

Abstract
Due to the complex marine environment factors such as wind and waves, FPSO (Floating Production Storage Offloading) relies on the mooring system for positioning and reducing the serious consequences when excessive hull movement happens. Therefore, the production, storage, and unloading operation of FPSO are directly affected by the safety of the mooring system. At present, installing the fiber grating strain sensor on the mooring system of FPSO is the primary way of system condition monitoring. However, the problems of sensors like dropping, deformation and short circuit reduce the reliability and increase costs in monitoring. In view of the above considerations, this paper proposes a real-time calculation method for motion response of mooring system of FPSO, basing on LSTM (Long and short-term memory) algorithm. In the case where the shipborne GPS (Global Positioning System) provides six degree of freedom, the force at the specific position on SYM (Soft Yoke Mooring) system can be directly calculated.
The feasibility of the load response calculation involving the critical position like pendant-hull interface and of YOKE head in FPSO SYM system is proved by comparison with the numerical simulation, providing a new method support for gradually replacing the force sensor based mooring response acquisition method, and an economical and efficient way for the real-time calculation of the key position response in the FPSO mooring system.
Numerical Investigation on Suction Pile’s Holding Capacity Installed in Carbonate-Type Soils
Authors: Cao Jianchun , Zhong Zhibin , Budhiraja Ashish 
Published: December 2020

Abstract
Suction piles have not been widely used in carbonate-type soils (i.e., muds/silts) because the pile skin frictions in this type of soils are only about 5% of that in normal clayey soils. The holding capacity of a suction pile installed in these types of soils may be affected by its lower friction. Moreover, pile designers have concerns not only on the development of the Reverse End Bearing (REB) but also on how long the REB can sustain. This paper presents the development of a three-Dimensional Finite Element Analysis (3D FEA) model and the analysis results to investigate the behavior of suction pile for different levels of skin frictions. Firstly, the FEA model is used to investigate the development of the Reverse End Bearing (REB) of a suction pile by assigning two different levels of pile external skin frictions, i.e., 5% and 100% (full skin friction). A vertical load is applied at the center of the pile top. Secondly, the FEA model is used to investigate the behavior of a suction pile for a very low level of pile skin friction (i.e., 5% skin friction). An inclined load with various load angles from horizontal is applied at the padeye (i.e., 16m below seabed). Thirdly, the load carrying (failure) mechanism has been checked by examining the total displacement vectors of soil masses around the pile. Fourthly, a sensitivity study is carried out to investigate the capacity of a suction pile for different usage factors of REB. Finally, suction pile design requirements for carbonate-type soils (i.e., low level of pile skin frictions) are recommended.
Estimating Swelling in Oil-Based Mud due to Gas Kick Dissolution
Authors: Manikonda Kaushik , Hasan Abu Rashid , Kaldirim Omer , Rahmani Nazmul , Rahman Mohammad Azizur 
Published: December 2020

Abstract
Gas kick is an ever-present hazard whose importance is magnified for offshore drilling situations. Modeling gas kick is a complex problem that requires an understanding of the relevant fluid dynamics as well as the solubility of natural gas in oil-based muds (OBM). Drilling fluid swelling due to natural gas solubility in OBM significantly affects the extent of pit gain — one of the primary indicators of a kick in progress. This paper specifically addresses the issue of drilling fluid swelling from gas dissolution in OBM.
Drilling fluid swelling due to gas dissolution is generally expressed the same way as oil swelling due to dissolved gas, by the volume factor, Bo. Many correlations for estimating Bo as a function of temperatures and pressures are available. We have developed a rigorous thermodynamic approach for estimating Bo. Our approach uses the Peng-Robison (1976) equation of state (EOS), van der Waals mixing rules, and binary interaction coefficients appropriate for drilling fluids to account for gas solubility. Solving the cubic form of the Peng-Robinson EOS yields a z-factor for the liquid phase of the mixture. The model uses this z-factor to estimate the liquid-phase volume of dissolved methane and, consequently, Bo. This paper validates the results of estimated Bo from this method with volume factor calculations obtained from Aspen HYSYS. Finally, this paper also presents a section where the methane mole fraction data at different P&T conditions, obtained from HYSYS simulations, is used to validate the solubility model previously developed by Manikonda et al. (2019).
Application of Experimental Design on Small Surface Boat for Resistance and Payload Study
Authors: Lin Chun-Cheng , Hsaio Yu-Chi 
Published: December 2020

Abstract
With commercialization, marine science and military applications in offshore and shallow waters is increasing, the development of the small surface vessels are getting greater, and that design targets are focus on multi-functional platforms, smart navigation and autonomous, etc. Therefore, the goals of multi-purpose small surface vessels such as the coastal patrol, offshore observation and data collection, intelligence reconnaissance, anti-mine warfare, marine shooting training targets, and so on. In currently, to achieve these missions, the length of most small surface vessels were designed less than 10 meters. Furthermore, based on these multi-propose requirements, this study will explore the configuration design of monohull and trimaran, combine the research source of the Horizontal Circulating Water Channel (HCWC), through the ship model test to acquire experimental data. In addition, to promote the study quality and experimental efficiency, we applied Taguchi design of experimental (DOE) and the variance of analysis (ANOVA) to compare the resistance and payload of various configurations ship design. In this study, we defined two control factors (such as factor-A is Longitudinal distance, factor-B is Lateral distance) and set up three-level factorial design, and planned factorial experiment based on Taguchi orthogonal array L9 (34). Also used the neural network and training metamodeling. This metamodeling was decided by relative coefficient (R) and decision coefficient (R2). According to this metamodeling, and then, applied the genetic algorithm to search the best solution such as A2B3. The results of this study showed that the resistance performance of the trimaran is better than the monohull while the volume Froude number Fr∇ &gt; 0.95, and the optimum configuration has greater resistance performance at both higher and lower speed fields to achieve robust design. In the other hand, this paper will also discuss the feasibility and effectiveness of the installation space and multi-function performance on platform. Hence, for payload study, we also applied ANOVA to analyze these nine different configurations, and indicated a significant main effect for factor-B. However, no significant main effect for factor-A and interaction effect were found. To conclude, this study may be of importance in explaining small surface vessel design, as well as in providing ship designer with a better understanding of trade-off about speed and payload. While this study has its limitations (such as HCWC characteristic dimension), it is hoped that it could as a basis for further study in the multi-functional small surface vessel.
Non-Linear Wave Run-Up Along the Side of Sailing Ships Causing Green Water on Deck: Experiments and Deterministic Calculations
Authors: van Essen Sanne , Bandringa Henry , Helder Joop , Buchner Bas 
Published: December 2020

Abstract
Experiments with a flat plate in oblique waves at different speeds, wave conditions, headings and drift speed were done to evaluate non-linear wave run-up along a sailing ship. Both the incoming and diffracted part of the run-up were highly nonlinear in all test conditions. The run-up was larger at 135 than at 150 deg heading, the influence of speed was small, wave steepness increased run-up up to the point of breaking and a drift speed decreased the run-up. Most of the observed differences were larger than the seed and basin variability. (Semi-) linear diffraction methods are not sufficient to predict the highest runup crests, but applying them to screen for critical events could be further studied. CFD is able to accurately predict the nonlinear run-up in such selected events. Combining different levels of tools seems the most efficient way to predict extreme wave events such as green water due to run-up.
Second-Order Difference-Frequency Loads on FPSOs by Full QTF and Relevant Approximations
Authors: Engebretsen Espen , Pan Zhiyuan , Fonseca Nuno 
Published: December 2020

Abstract
This paper investigates three different approximations of the full Quadratic Transfer Function (QTF) for calculating horizontal plane second-order difference-frequency loads on FPSOs, namely Newman’s approximation, full QTF without free surface integral and the white-noise approximation.
Second-order excitation loads obtained from approximated QTFs are compared in frequency-domain with those obtained by the full QTFs computed from second-order diffraction/radiation analysis in WADAM. The comparison is performed for a new-build FPSO in a range of water depths and environmental combinations. The full QTFs from second-order diffraction/radiation analysis are further compared to empirical QTFs as identified from cross bi-spectral analysis of model test results in irregular waves.
A mesh convergence study is presented for calculating full QTFs by the near-field approach in a second-order diffraction/radiation analysis. The importance of including viscous damping in heave, roll and pitch is illustrated for the mean wave-drift force in surge and sway.
FPSO motions and mooring line tensions from fully-coupled time-domain analysis in OrcaFlex is compared when using approximated QTFs and full QTFs from second-order diffraction/radiation analysis.
Experimental Study on the Behavior of a Bubble in the Vicinity of an Air Bubble Attached to a Fixed Structure
Authors: Wang Jia-xia , Liu Kun 
Published: December 2020

Abstract
The interaction between a spark-generated bubble and a non-oscillating air bubble attached to a horizontal rigid plate is investigated using a low-voltage spark-discharge setup. Large numbers of fascinating and complicated interactions are given rise during two bubble coupling pulsation due to the deformation property endowed to the plate through an air bubble attached. It is found that, under the combined influence of the cavitation and the structure, some complex phenomenon likes the bubble coalescence, air bubble skirt phenomenon, bubble splitting are given rise during the two bubble interaction procedure. The coupling phenomenon between the spark generated bubble, air bubble and the structure are discussed in detailed The mainly attention are paid to the coupled response of an attached quiescent bubble under oscillating bubble, the effect of the distance parameter and volume ratio parameter on the air bubble shapes are analyzed in detail, and the mechanism behind these phenomenon are investigated. Our study can be a useful scheme in the protection of a naval structure from threats induced by an explosion bubble impact loading.
Damping of Regular Waves in Model Ice
Authors: Hartmann Moritz C. N. , von Bock und Polach R. U. Franz , Klein Marco 
Published: December 2020

Abstract
Wave characteristics change significantly when the waves propagate in a solid ice field. The damping of the incident waves due to the presence of the ice sheet has a significant impact on the modification of wave propagation and dispersion.
In this study the interaction of waves with solid ice are investigated by means of model tests. The objective of the study is to measure wave and ice characteristics and analyze the data regarding wave damping and the change of wave parameters in model ice.
The experiments were performed in the ice tank of the Hamburg ship model basin (HSVA) with a set of regular waves with varying wave number and steepness. The surface elevation of the waves is recorded by acoustic and motion capturing measurement devices.
By comparing the measurements of the incident open water waves with the waves in ice, the change in terms of wave amplitude and dispersion due to the presence of ice is analyzed.
It is shown that once the waves travels through the ice the angular frequency remains unchanged while the wave amplitude exponentially decays, with an increasing decay coefficient at smaller wave length. Furthermore, the dispersion relation in ice, represented by the measured angular frequency and wave number, is consistent with the theoretical dispersion relation.
Continuous Drilling Sensor Data Reconstruction and Prediction via Recurrent Neural Networks
Authors: Tunkiel Andrzej T. , Wiktorski Tomasz , Sui Dan 
Published: December 2020

Abstract
There is an ever-increasing amount of data being recorded in oilfield operations. During drilling a well a large number of parameters is being monitored and saved, often reaching several hundreds. We are seemingly monitoring everything, from basic parameters such as Weight on Bit, Torque, and Rate of Penetration (ROP), to the exhaust temperature of engine no. 3. Unfortunately, the quality of collected data does not match the quantity. Critical sensors, such as gamma and inclination, are often lagging many meters behind the bit. Despite best efforts, sensors stop working, hard drives corrupt files, and data mud pulse telemetry uplinks fail. Methods of infilling data spanning many meters or minutes are necessary. We present a novel approach that enables reliable prediction of data lagging behind the bit through deep neural networks by merging trend-based prediction with traditional neural network approach. We were able to predict continuous inclination data in a curved section of a well with an average absolute error of only 0.4 degrees up to 20 meters from last known value.