bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Numerical Method for Ice Resistance Calculation of Polar Ships Navigating in Floating Ice Region
Authors: Li Hui , Qian Yuan , Feng Yan , Sheng Weijia , Li Haojin 
Published: November 2019

Abstract
This paper presents a numerical method for forecasting the ice resistance of polar ships navigating in floating ice region. The finite element method is adopted to analyze the interaction between ship and floating ice including the coupling effect between ice and water. Based on the comparison between the sea ice test data and the numerical simulation of the ice model, it is verified that the numerical method can successfully simulate the characteristics of sea ice materials. The accuracy of the numerical method is validated against ice tank model test. By using this method, the resistances of a polar ship navigating in floating ice region with different ice coverage rate (60%, 70%, 80% and 90%) at different speeds are calculated. The results show that the ice coverage rate has a great influence on the ice resistance, and the ice resistance varies with ship speeds.
A PDE Model for Estimating the Life Time of a Riser
Authors: Gustad Halvor Snersrud , Moe Per Thomas , Celledoni Elena 
Published: November 2019

Abstract
Subsea intervention operations may expose wellheads to very high structural loads. Traditionally, structural fatigue was not regarded as a challenge for wellheads, and design codes did not include verification with respect to structural loads. However, development in mathematical modeling and numerical techniques as well as monitoring systems have revealed that semi-submersible rigs with marine riser systems and BOP (Blowout Preventer) can cause quite significant loads on permanently installed equipment.
Being able to describe a risers movement under the action of external forces is important in order to calculate the effects on the wellhead. This may be used to predict the expected remaining lifetime of the system. In this article, the existing literature on numerical modeling of a riser system is discussed. Different mathematical models of a riser system were approximated numerically by a finite element method. The models are compared and their correctness is discussed. The error bounds for the finite element solutions are derived. Boundary conditions are further developed to improve realism and ensure compliance with existing standards and guidelines. The sensitivity of such changes are assessed and discussed. A discussion on how to use the numerical simulated data to train a machine learning algorithm to estimate well loading is presented and key parameters affecting the cyclic wellhead loads are identified.
The Ocean Cleanup System 001 Performance During Towing and Seakeeping Tests
Authors: Sterenborg Joost , Grasso Nicola , Schouten Rogier , Tjallema Arjen 
Published: November 2019

Abstract
One of the aims of The Ocean Cleanup is to develop technologies to extract plastic pollution from the world’s oceans. Several concepts of passive floating systems were considered that are supposed to confine plastics to ease their collection. Such concepts consist of a floating member and a submerged flexible skirt and have in common that their span is generally more than 500 meters. Consequently, fluid-structure interaction plays an important role in the response of such a floating system. To support numerical simulations, MARIN carried out extensive model tests on a 120 meter system section of the final concept, with focus on the fluid-structure interaction (FSI) of the submerged skirt in operating conditions and in towing configuration. The ability to capture plastics was not investigated in these model tests. Novel for wave-basin tests were non-intrusive measurements using underwater Digital Image Correlation (DIC) to obtain the displacements and deformations of the flexible skirt. DIC proved to be a capable measurement technique for this type of structure in combination with a wave basin. Detailed quantitative data on skirt motions and deformations were delivered and the last concept of the cleanup system was tested in the towing configuration and operational configuration.
Multi-Pronged Approach for the Design of HP/HT Deepwater Steel Catenary Risers
Authors: Bangalore Gurudutt , Cheng Yongming , Banumurthy Surya 
Published: November 2019

Abstract
As the industry plans to move forward with the development of high pressure and high temperature (HP/HT) fields, challenges exist for the design of complaint risers in deepwater applications. The conventional wet tree application risers such as Steel Catenary Risers (SCRs) have proven to be mature technologies in the deepwater applications around the world. HP/HT application leads to many challenges in deepwater risers. This paper investigates ways to overcome the design challenges of deepwater SCRs using a multi-pronged approach.
The paper first addresses the challenge in riser pipe wall thickness. The HP/HT applications require higher pipe wall thicknesses mainly governed by the burst pressure design requirements. The pipe wall thicknesses required for the HP/HT applications will result in very high installation loads, reeling issues with low D/t, fabrication (welding) challenges, high payloads to the host vessel, etc. Any optimization to the wall thickness design in terms of using higher grade material, advancements in welding technology and advantages to be gained in the use of design codes can potentially help in overcoming of these challenges.
The pipe sizes used in the HP/HT applications can pose significant challenges to the touchdown zone (TDZ) of standard steel catenary riser configurations, in terms of experiencing large TDZ compressions and having fatigue life concerns. Use of different SCR problem-solving approaches — TDZ clump weights, Lazy Wave Steel Riser (SLWR) and weight optimized risers will be reviewed in this paper.
Vessel motion characteristics can significantly affect the riser performance. Vessels with improved motions, particularly from the riser response viewpoint, can play a significant role in the selection of optimum riser configurations. This has to be achieved in the early stages of the project. Some of the work done recently in development of the optimized vessel performance particularly in the case of semi-submersibles and their implications on the riser design are studied in this paper.
Design of the risers in HP/HT fields in deepwater applications presents significant challenges and requires a multi-dimensional problem solving approach. An example is provided in this paper for the investigation. A multi-pronged approach has to be adopted for the successful design of riser system for HP/HT deepwater applications.
Concept Design of Very Large Floating Structures and Laboratory-Scale Physical Modelling
Authors: Cappietti Lorenzo , Simonetti Irene , Crema Ilaria 
Published: November 2019

Abstract
The use of Very Large Floating Structures, VLFS, may represent a strategic approach in order to cope with some of the future societal challenges arising from the impressive growth of the world population. In this article, the motivations of this perspective are briefly discussed, the main issues for the development of VLFS are summarized and a concept structural design based on building-blocks technology is proposed. A small-scale physical model was manufactured and tested in the wave-current flume of the Laboratory of Maritime Engineering, LABIMA, of the Florence University, Italy. The aim of this study is the assessment of the structural feasibility and the effectiveness of the proposed VLFS concept, in terms of resistance to wave loads and control of floating behavior. The experimental measurements provide a first contribution to the necessary knowledge, about load magnitudes and floating behavior, for sizing some of the key structural components. The results appear to support the feasibility of the system in terms of usage of structural materials, technical components and building technologies, available at present, that can withstand the measured loads. Moreover, the acquired experimental database is fundamental in order to validate numerical models, in the perspective of using also such tools as complementary methodology for further improvement of the knowledge of design issues.
Recent Developments on Welding, NDT and ECA of Clad and Lined Offshore Pipelines
Authors: Zumpano Petrônio , Garmbis Alexandre G. , Moraes Diogo O. , Hirata Fausto , Cunha Bruno R. M. , Hippert Eduardo , Paes Marcelo T. P. 
Published: November 2019

Abstract
Due to the level of contaminants of Brazilian pre-salt fields, alloy 625, e.g. UNS N06625, clad or lined steel linepipes have been chosen in order to resist such environmental conditions. Recent advances on welding, non-destructive testing (NDT) and Engineering Critical Assessment (ECA) approaches for bimetallic materials have significantly changed since discussed in OMAE-2012. Regarding welding of alloy 625 clad and lined pipes, maximum welding interpass temperature, back purge gas control, root discoloration, visual inspection, root profile for fatigue performance and other issues are discussed herein. The Fatigue Crack Growth Rate (FCGR) to be adopted for alloy 625 is still one of the issues, since curves for alloy 625 in specific environment are normally not available. New appendix C of DNVGL-RP-F108 gives orientations regarding how to conduct tests in sour environment. DNVGL JIP on clad and lined material has made an extensive approaching of the undermatching condition of alloy 625 weld metal under different design strain levels. Regarding NDT, developments and improvements in Automated Ultrasonic Testing (AUT) methods have been obtained for inspection of Corrosion Resistant Alloy (CRA) girth welds and weld overlay. Film and digital radiography are still used for the inspection of the pipe end of the mechanically lined pipe, but ultrasonic solutions are under development. Welding and NDT challenges of alloy 625 reported in 2012 have been overcame by state-of-art technologies used in offshore rigid risers construction and installation. Alternative CRA materials are under research and development, but alloy 625 still is the most reliable option.
Performance of a Passive Tuned Liquid Column Damper for Floating Wind Turbines
Authors: Yu Wei , Lemmer Frank , Cheng Po Wen 
Published: November 2019

Abstract
The motivation of the present paper is to show the proof-of-concept of a passive Tuned Liquid Column Damper (TLCD) for floating wind turbines, which increases the platform pitch damping and power production under wind and wave excitations. As the first step, a reliable TLCD model is implemented and coupled with a reduced order floating wind turbine model. Here, the TLCD is modelled as a second order system which is known for ships, whereas the structural model is a coupled aero-hydro-servo-elastic model with five degrees of freedom. The results show that the TLCD is able to damp the platform resonances but to a limited extent, which is inline the findings of previous research. However, the improved platform pitch stability allows a larger blade pitch control bandwidth, which is normally limited by the underdamped soft support platform. Therefore, by introducing the passive TLCD into the floating wind turbine system, a better power production is achieved.
The Effect of Aspect Ratio on the Drag of Bare Cylinders
Authors: Potts Douglas A. , Binns Jonathan R. , Potts Andrew E. , Marcollo Hayden 
Published: November 2019

Abstract
The drag coefficient for long-slender structures that is typically provided in design guidance has been determined from test specimens of sufficient length that they are unaffected by the aspect ratio (L/D), whereby they are considered to be of “infinite” length. However, it is apparent from the literature that aspect ratio does have a significant non-linear effect at short L/D ratios. DNV provides guidance on the aspect ratio effect on the drag coefficient of a cylinder, for which no experimental source data has been cited. The DNV design guidance has wide usage in the offshore industry and merits critical evaluation. This paper critically reviews the literature and presents the results of a series of tow tank experiments performed by the authors. A series of tow tank tests of a surface-piercing cylinder has been undertaken using a range of aspect ratios as well as testing the effect of various end conditions, where the effects of VIV and ventilation has been deemed insignificant. Correlation of the various data sets of the literature and the experimental test programme provides the basis for developing an alternate design guidance curve for the effect of aspect ratio on the drag coefficient of cylinders.
Evaluations of Ductile and Cleavage Fracture Using Coupled GTN and Beremin Model in API X70 Pipelines Steel
Authors: Jang Youn-Young , Moon Ji-Hee , Huh Nam-Su , Kim Ki-Seok , Cho Woo-Yeon , Lee Myeong-Woo , Kim Yun-Jae 
Published: November 2019

Abstract
This paper is aimed to characterize ductile and cleavage fracture behavior of API X70 pipeline steel and investigate applicability of a micro-damage mechanics model to simulate static and dynamic crack propagation of single-edge notched tension (SENT) and drop-weight tear test (DWTT) specimens, as well as a local approach to describe cleavage fracture behavior. Gurson-Tvergaard-Needleman (GTN) model was applied to simulate ductile fracture behavior of SENT and DWTT specimens, where GTN model has been widely known for well-established model to characterize micro-damage process of void nucleation, growth and coalescence. As for a local approach, Beremin model was considered to estimate probability of cleavage fracture. In this regard, this study was especially focused on abnormal fracture appearance of DWTT specimen.
In the present study, firstly, experiment data from tensile specimen test was used to obtain plastic flow curve (i.e. stress and strain curve). And load-CMOD and J-integral/CTOD resistance curves obtained from SENT test were used to characterize static ductile fracture and calibrate GTN model parameters for X70 pipeline steel. And the calibrated GTN model parameters were verified by comparing experiment data from DWTT test such as load-displacement and crack length-time curves with those from FE analysis. To accommodate dynamic effect on material properties, rate-dependent stress-strain curves were considered in FE analyses. To describe cleavage fracture, the Weibull stress was calculated from FE analyses of DWTT and Weibull parameters were calibrated by comparing with probability distribution of cleavage fracture from experiment data of DWTT specimen. Using Weibull parameters, the whole of cleavage fracture probability can be estimated as ductile shear area of DWTT specimen increases.
Hydrodynamic Investigation of a Novel Concept of OWC Type Wave Energy Converter Device
Authors: Rezanejad Kourosh , Guedes Soares Carlos 
Published: November 2019

Abstract
In the present study, the hydrodynamic performance of a novel and efficient concept of a floating Oscillating Water Column device has been investigated. The new concept consists of two chambers that are placed in the upstream (fore chamber) and in the downstream (rear chamber) with respect to the incident wave direction. The rear chamber acts mainly similar to a Backward Bent Duct Buoy system, while the design of the fore chamber follows conventional types of Oscillating Water Column systems with the harbour plates (bottom plate as well as side plates) elongated outside of the fore chamber. The primary efficiency of the devised concept has been investigated in the frequency domain. In this context, to solve the corresponding diffraction and radiation problems due to the influence of the air pressure inside the chambers as well as motions of the body, an in-house code has been developed in 2D using the Boundary Element Method based on linear wave theory. The obtained numerical results show that the introduced concept has advanced hydrodynamic efficiency in a broad range of waves.
A Critical Examination of the Hysteresis in Wells Turbines Using CFD and Lumped Parameter Models
Authors: Ghisu T. , Cambuli F. , Puddu P. , Virdis I. , Carta M. , Licheri F. 
Published: November 2019

Abstract
The hysteretic behavior of OWC-installed Wells turbines has been known for decades. The common explanation invokes the presence of unsteady aerodynamics due to the continuously varying incidence of the flow on the turbine blades. This phenomenon is neither new nor unique to Wells turbines, as an aerodynamic hysteresis is present in rapidly oscillating airfoils and wings, as well as in different types of turbomachinery, such as wind turbines and helicopter rotors, which share significant similarities with a Wells turbine. An important difference is the non-dimensional frequency: the hysteresis appears in oscillating airfoils only at frequencies orders of magnitude larger than the ones Wells turbines operate at. This work contains a reexamination of the phenomenon, using both CFD and a lumped parameter model, and shows how the aerodynamic hysteresis in Wells turbines is negligible, and how the often measured differences in performance between acceleration and deceleration are caused by the capacitive behavior of the OWC system.
An Iterative Updating Method for Dynamic Responses of a Floating Platform Under Action of Internal Solitary Waves
Authors: Junrong Wang , Junfeng Du , Min Zhang , Anteng Chang 
Published: November 2019

Abstract
The internal solitary waves, have properties of two-way shear profile, significant velocity and acceleration, etc., which threaten the safety of deepwater floating systems in South China Sea (SCS), for the frequent occurrence and the high intensity of internal solitary waves in SCS. In recent years, offshore oil companies of China encountered many strong internal waves during its deepwater oil and gas exploration and development activities in South China Sea. However, the action mechanism of ISWs to floating structures is not understood clearly, and the internal solitary waves are classified as ocean current in API RP 2SK (3rd edition), therefore engineers ignore the velocity variance and long period “wave” characteristics in the design of floating structures. Furthermore, the offshore floating structures is oscillating under the action of environmental forces, due to the horizontal velocity of the platform is comparative to that of ISWs, thus fluid-body coupling is significant that one cannot analyse it by simply adding a specified ISW force time history to the floater. This paper proposes a new iterative updating method for ISW loading calculation considering the fluid-body coupling, and applied this method to a semi MODU, numerical study shows the iteration is efficient and the result is more reasonable compared to conventional method, and it is found that the maximal offset decreases significantly.
Global Assessments of Surface Winds and Waves From an Ensemble Forecast System Using Satellite Data
Authors: Campos Ricardo Martins , Guedes Soares C. 
Published: November 2019

Abstract
This paper evaluates the 10-m wind intensities and significant wave heights from the NCEP Ensemble Forecast System using altimeter data. A total of 20 perturbed members plus a control member (deterministic run) compose the ensemble. The assessment is focused on the comparison between the control run and the ensemble mean, in terms of benefits presented by four error metrics. Four satellite missions are selected for the assessments, obtained from AVISO and NESDIS/NOAA databases. Results show that the scatter components of the errors strongly depends on the latitude, were extra-tropical locations at longer forecast times present large errors. A significant improvement using the ensemble forecast compared to deterministic runs was verified at these locations, where the RMSE of day 10 was reduced from 5 to 3.5 m/s for U10 and from 1.8 to 1.3 meters for Hs.
Direct Time Domain Simulations for a FPSO Tandem Offloading Operation
Authors: Koo Bonjun , Jegannathan Manoj , Kyoung Johyun , Lim Ho-Joon 
Published: November 2019

Abstract
In this study, direct time domain offloading simulations are conducted without condensing the metocean data using High Performance Computing (HPC). With rapidly growing computing power, from increased CPU speeds and parallel processing capability, the direct time domain simulation for offloading analyses has become a practical option. For instance, 3-hour time domain simulations, covering the entire service life (e.g. 100,000 simulations for 35 years) of a floating platform, can now be conducted within a day. The simulation results provide realistic offloading operational time windows which consider both offloading operation sequence (i.e. berthing, connection, offloading duration and disconnection) and required criteria (i.e. relative responses, loads on hawser and flow line, etc.). The direct time domain offloading analyses improve the prediction of offloading operability, the sizing of the FPSO tank capacity, and the shuttle tanker selection. In addition, this method enables accurate evaluations of the economic feasibility for field development using FPSOs.
System Identification of Abkowitz Model for Ship Maneuvering Motion Based on ε-Support Vector Regression
Authors: Liu B. , Jin Y. , Magee A. R. , Yiew L. J. , Zhang S. 
Published: November 2019

Abstract
System identification is crucial to predict the maneuverability of the ship. In this work, ε-support vector regression (ε-SVR) is implemented to identify hydrodynamic derivatives of Abkowitz maneuver model. A proposed technique, batch learning, is implemented with the addition of Gaussian white noise to reconstruct the samples and alleviate the parameter drift in the system identification of the ship maneuvering model. The predicted results are compared with results obtained from Planar Motion Mechanism (PMM) test. Standard maneuvers, 35° turning circle, 10°/10° and 20°/20° zigzags, are simulated and compared with the predicted model by ε-SVR. The presented results show that the proposed batch learning technique with Gaussian white noise is an effective technique, which improves the accuracy and robustness of ε-SVR in system identification. The results obtained from the predicted model match well with the those obtained from PMM results, which shows its excellent generalization performance. The developed model is applied to understand control requirements for vessels under different conditions.