bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Investigation on Surface Crack Growth in Steel Plates Repaired With Carbon Fiber-Reinforced Polymer
Authors: Li Zongchen , Jiang Xiaoli , Hopman Hans 
Published: November 2019

Abstract
Fatigue crack growth is a major challenge to the structural integrity of steel structures. In technical practice, surface cracks are of great importance since cracks in components and structures often exhibit this geometry. Fiber-reinforced polymer (FRP) strengthening technology is a reliable technique to repair cracks in steel structures. Yet the investigation on FRP repairing surface cracks in steel structures is lacking. What’s more, the crack growth might cause crack-induced debonding at the interface of FRP reinforcement, generating negative effects to the reinforcement effectiveness. Unfortunately, there are limited studies in the open literature for this issue. In this paper, we conduct the investigation on surface crack growth in steel plates reinforced with Carbon Fiber-reinforced polymer (CFRP) under tensile load. Three-dimensional finite element models are built to predict the stress intensity factors of the surface cracks. The crack-induced debonding is considered in the finite element analysis by introducing the cohesive zone model and a bond failure criterion. In accordance with Paris law, surface crack growth rate of different models are predicted. The influential parameters of crack-induced debonding are analyzed by means of parametric studies. The results indicate that CFRP reinforcement could significantly decrease the surface crack growth rate, while the crack-induced debonding might generate negative effect on CFRP reinforcement. In addition, the crack-induced debonding is affected by not only the interfacial properties, but also the reinforcement scheme, such as thickness of the adhesive layer, CFRP layer number and its elastic modulus, and the depth of surface cracks.
A Calculation Method for the Quasi-Stationary Pressure in Cabin Explosion With Venting
Authors: Zhao Pengduo , Wang Haojie , Du Zhipeng , Li Xiaobin 
Published: November 2019

Abstract
The explosion in the closed cabin will cause a sharp rise in cabin gas pressure, which will cause serious damage to the cabin structure. The quasi-stationary pressure, due to its long duration and large impulse, plays a major role in the destruction of the structural strength of the entire cabin. The venting holes on the transverse bulkheads can effectively guide the release of energy to other locations, reducing the damage to the cabin.
In this paper, the quasi-stationary pressure generated during cabin explosion with venting is studied. According to the conservation of mass and energy, the cabin explosion model with venting is transformed into an equivalent high pressure gas release model to simulate the initial instantaneous state of cabin explosion, and it is verified by finite element calculation that the two models are equivalent in predicting quasi-stationary pressure. The entire gas flow process during the exploding with venting holes is divided into two parts: the gas flow in the cabin to the venting hole and the venting hole to the atmosphere. An approximate analytical method for predicting quasi-stationary pressure generated during cabin explosion with venting is improved by using Bernoulli equation and isentropic compression formula of ideal gas, and the results of the improved calculation method are compared with the results obtained by the numerical simulation method to verify its validity.
Strategies to Minimise Numerical Ventilation in CFD Simulations of High-Speed Planing Hulls
Authors: Gray-Stephens Angus , Tezdogan Tahsin , Day Sandy 
Published: November 2019

Abstract
Numerical Ventilation (NV) is a well-known problem that occurs when the Volume of Fluid method is used to model vessels with a bow that creates a small, acute entrance angle with the free surface. These are typical of both planing hulls and yachts. There is a general lack of discussion focusing upon Numerical Ventilation available within the public domain, which is attributable to the fact that it only affects such a niche area of naval architecture. The information available is difficult to find, often fleetingly mentioned in papers with a different focus. Numerical Ventilation may be considered one of the main sources of error in numerical simulations of planing hulls and as such warrants an in-depth analysis. This paper sets out to bring together the available work, as well as performing its own investigation into the problem to develop a better understanding of Numerical Ventilation and present alternate solutions. Additionally, the success and impact of different approaches is presented in an attempt to help other researchers avoid and correct for Numerical Ventilation.
Interface smearing caused by the simulations inability to track the free surface is identified as the main source of Numerical Ventilation. This originates from the interface between the volume mesh and the prism layer mesh. This study looks into the interface to identify strategies that minimise Numerical Ventilation, presenting a novel solution to prism layer meshing that was found to have a positive impact. Through the implementation of a modified High Resolution Interface Capture (HRIC) scheme and the correct mesh refinements, it is possible to minimise the impact of Numerical Ventilation to a level that will not affect the results of a simulation and is acceptable for engineering applications.
Hydrodynamic Modelling and Estimating Response of Glacial Ice Near a Drilling Rig
Authors: Ommani Babak , Berthelsen Petter Andreas , Lie Halvor , Aksnes Vegard , Løland Geir 
Published: November 2019

Abstract
Impact scenarios involving a typical drilling rig and glacial ice are studied. The goal is to better identify the important physical effects in modelling the dynamics of glacial ice in presence of waves and a floating platform, whilst improving simulation tools to capture the location and energy of possible collisions. A state-of-the-art numerical model of a typical semi-submersible is developed and calibrated with model tests to represent the drilling rig. A systematic incremental approach is adopted to model the dynamics of glacial ice. Long wave approximation, nonlinear excitation and restoring forces, interaction forces with the semi-submersible, and viscous forces due to flow separation are among the models which are considered step by step. The sensitivity of the resulted collision scenario to the modelling choices is investigated. The possibility of impact with columns, pontoons, and risers are particularly studied. Based on the obtained results, recommendations are made for modelling of glacial ice dynamics in presence of a floating platform.
A Study on Unification of Welding Consumables in Construction of Chemical Cargo Tanker Made of Duplex Stainless Steel: Evaluation of Static Strength of Welded Joint
Authors: Yotsuzuka Takayuki , Endo Yusuke , Niino Eiji , Gotoh Koji 
Published: November 2019

Abstract
Austenitic stainless steels such as SUS 316 LN and austenitic stainless clad steel are used in cargo holds of chemical tankers owing to their corrosion resistance. Recently, the use of duplex stainless steels has been increasing, owing to their better strength and corrosion resistance and lower content of expensive Ni, compared with those features of austenitic stainless steels. However, few duplex stainless clad steels have been approved by classification bodies. Furthermore, the application of duplex stainless steel is not yet mainstream as hull structural materials because a stable supply market has yet to be established. Therefore, when applying cladding steel to construction of chemical tankers, austenitic stainless clad steel is often used at present. The duplex stainless steel and the austenitic stainless clad steel are mixed at construction factories; hence, there is a risk of misuse of welding consumables. If misuse is suspected, it is not possible to judge the erroneous use from visual inspection after construction; therefore it is necessary to uniformly remove the weld and re-weld. However, if universal welding consumables were identified, this might avoid the problems of misuse and simplify the procurement of welding materials.
In this paper, we report on our studies to verify welding consumables for use in the hull structures, involving a mixture of duplex stainless steel and the austenitic stainless clad steel. The static strength of the welded joints is a particular focus of this study, from which we confirmed the validity and limitations of welding consumables.
Study on Attitude Control of a Cabin-Suspended Catamaran by Using a Double-Loop Control System
Authors: Han Jialin , Kanno Sota , Mochizuki Akito , Kitazawa Daisuke , Maeda Teruo , Itakura Hiroshi 
Published: November 2019

Abstract
A series of cabin-suspended ships, named Wave Harmonizer, has been developed since 2008. The model ship consists of cabin part, hull part and conjunction part which is mounted in-between the cabin and the hull. The possibility and feasibility of introducing suspensions into small vessels are investigated. Effectiveness evaluations are made in two aspects: motion reduction of the cabin and wave energy harvesting through the oscillating cabin. According to the research results obtained in 2015 and 2016, it was found that the deck of the cabin may bear obvious inclination while weights were loading or unloading from it. Moreover, in relative long waves, the effectiveness of the motion reduction of the skyhook controller was insufficient. To solve those problems, an attitude control strategy is proposed. It is adopted as an outer-loop of the existing controller. Inclination sensors are employed to collect the rotational angle of the cabin in terms of pitch and roll. After finishing the design and construction of the double-loop control system, open loop tests are carried out in dry and wet conditions. The chain mechanism of the ship is investigated. Then a bench test is operated to validate the control concept and performance of the double-loop control system. Finally, tank tests are implemented to examine the inclination reduction of the cabin at regular head waves. In this paper, the development of the double-loop control system is described, experimental results are demonstrated with respect to the heave and pitch motion reduction of the cabin at the condition of with/without the outer control loop. It shows that the inclination reduction at the loading/unloading condition and the walking-on-deck condition are significant. However, in waves the effectiveness is not clearly verified. It suggests that the influence of the apparent gravity on the inclination measurement in waves should be investigated and solutions to accurately detect the inclination of the cabin should be sought.
Validation of the Motion Analysis Method of Floating Offshore Wind Turbines Using Observation Data Acquired by Full Scale Demonstration Project
Authors: Yoshimoto Haruki , Kamizawa Ken 
Published: November 2019

Abstract
In recent years, the social demands for the introduction of renewable energy are increasing, demonstration projects of floating offshore wind turbine are being implemented and planned around the world. In Japan, a demonstration test named Fukushima FORWARD (Fukushima Floating Offshore Wind Farm Demonstration Project) has been conducted since 2011. Fukushima FORWARD is a project carried out by the Ministry of Economy, Trade and Industry, the world’s first floating offshore windfarm with a total capacity of 14 MW, including three floating offshore wind facilities and one floating offshore substation. In Fukushima FORWARD, Japan Marine United Corporation is in charge of floater part EPCI (Engineering, Procurement, Construction and Installation) of one floating offshore wind facility and one floating offshore substation.
The floating offshore wind turbine (Ship Name: Fukushima Hamakaze) designed and built by Japan Marine United Corporation is equipped with a downwind 5 MW wind turbine. The floating structure adopts the advanced spar shape in order to reduce wave frequency motions and is moored by six spread catenary mooring lines.
In the design of floating offshore wind turbines, it is important to estimate motions with high accuracy. Especially floating offshore wind turbine equipped with horizontal axis wind turbine requires heavy RNA (Rotor Nacelle Assembly) to be installed on the tower, and the floater motion greatly influences the design of the tower base. The tower base is required to have sufficient reliability because it directly leads to collapse of the wind turbine if it is damaged. On the other hand, the tower base is generally constructed with a cylinder made of extremely thick steel plate which is difficult to bend and weld, and if it has excessive safety factor the cost has increased greatly. Also, estimating the motion is the basis for estimating the load on the floating structure.
In this paper, statistical analysis of long-term data measured by Fukushima FORWARD floating offshore wind turbine focusing on the motion and its features are introduced. In addition, we compare the motion obtained by potential theory and coupled analysis with actually measured motion using the measured wave and wind data and evaluate the validity of the analysis method.
Spatial and Seasonal Variability of Metocean Design Criteria in the Southern South China Sea From Covariate Extreme Value Analysis
Authors: Anokhin Vadim , Ross Emma , Randell David , Jonathan Philip 
Published: November 2019

Abstract
This paper describes spatial and seasonal variability of metocean design criteria in the southern South China Sea. Non-stationary extreme value analysis was performed using the CEVA approach (Covariate Extreme Value Analysis,[1]) for a 59-year long SEAFINE hindcast of winds and waves, estimating metocean design criteria up to 10,000-year return period. Wind design criteria are mostly driven by large-scale monsoonal events; at higher return periods infrequent cyclonic events have strong influence on the tail of the extreme value distribution but confined to a limited geographical area. The CEVA analysis of waves showed much less dependence on the tropical cyclone events; the spatial metocean design criteria were smoother, mostly influenced by the monsoonal wind strength, fetch and local bathymetry. Return value estimates illustrate the strong seasonality of metocean design criteria, with boreal winter (December-February, Northeasterly monsoon) contributing most to the extremes, while April and May are the mildest months. Estimates for the ratio of 10,000/100-year return values are also presented, both for winds and waves. There is empirical evidence that the range of “typical” values of generalised Pareto shape parameter observed for Hs is different to that observed for wind speed. For this reason, an upper bound of +0.2 for generalised Pareto shape was specified for wind speed analysis, compared to 0.0 for Hs. In some cases, increase of upper bound for waves to 0.1 is justified, leading to slightly more conservative Hs values. We confirmed that the upper end point constraint was not too influential on the distributions of generalised Pareto shape parameter estimated. Nevertheless, it is apparent that specification of bounds for generalised Pareto shape is a critical, but problematic choice in metocean applications.
Mechanical Modeling of the Polymeric Coating on a Subsea Pipeline
Authors: Vestrum Ole , Langseth Magnus , Børvik Tore 
Published: November 2019

Abstract
Offshore pipelines may be exposed to a range of extreme loading situations during operation on the seabed such as impact by trawl gear or anchors. While not primarily being designed for it, thermal insulating polymeric coatings are experienced to provide beneficial contributions to the structural integrity of subsea pipeline designs. In recent editions, the prevailing standards and design guidelines are allowing for the inclusion of external coating products in the mechanical design evaluation. This secondary functionality of insulating coatings presents a great potential in terms of more optimized pipeline designs. However, due to the lack of reliable and versatile mechanical models, any beneficial effects from these complex polymeric insulating coatings are often omitted in simulations. This work presents a finite element based approach for assessing the mechanical response of polymeric coatings on offshore pipelines with different porous structures imaged using X-ray micro computed tomography. The modeling approach is also compared with experimental results.
Validation of Hydrodynamic Loads on a Large-Diameter Monopile in Regular Waves
Authors: H. Dadmarzi Fatemeh , Thys Maxime , Bachynski Erin E. 
Published: November 2019

Abstract
Validated hydrodynamic load models for large-diameter support structures are increasingly important as the industry moves towards larger offshore wind turbines. Experiments at 1:50 scale with stiff, vertical, bottom-fixed, extra-large (9m and 11m diameter full-scale) monopiles in steep waves are conducted. The tests are carried out at two water depths, 27 m and 33 m. A range of regular waves, with varying period and amplitude, are used. The first, second, and third harmonics of the total wave loads, where measurements are available, are calculated with different methods. For the first harmonic of the force (and consequently the mudline moment), MacCamy-Fuchs gives the best agreement with experiments, especially for the larger diameter model. For the second harmonic, for the shortest waves the generalized FNV theory and Morison equation overpredict the forces, while for the longest (and largest) waves, the opposite is observed. The third harmonic of the force is generally overpredicted by the calculations.
Experimental Study on Coupled Motions of a Spar-Buoy Under Mathieu Instability
Authors: Iseki Toshio , Xu Peng 
Published: November 2019

Abstract
A series of experiments were carried out to investigate the occurrence of the Mathieu-type instability. The main objective of this study is utilization of an auto-parametrically excited oscillation for wave energy converters. In this paper, the subject is the auto-parametrically excited oscillation of a spar-buoy type point absorber with two degrees of freedom. A small spar buoy model with a ballast controlling system was made and the model experiments were conducted to realize the large oscillating motion based on the Mathieu-type instability. The ballast controlling system is installed in the buoy model and the vertical movement of the ballast produces a certain change of the pitching natural period. Using the controlling system, the pitching motion in regular waves under the heave resonant period was measured. In some experiments, it was observed that the large pitching motion occurred suddenly, and the time histories showed different excitation pattern from the theoretical Mathieu-type instability. Based on the model experiments and considerations of the theory of Mathieu-type instability, the occurrence of the large pitching motion is discussed.
Data Assimilation of the Stereo Reconstructed Wave Fields to a Nonlinear Phase Resolved Wave Model
Authors: Watanabe Shogo , Fujimoto Wataru , Nose Tak , Kodaira Tsubasa , Davies Graham , Lechner Daniel , Waseda Takuji 
Published: November 2019

Abstract
A stereo camera system was installed facing Southeast at the observational tower owned by the University of Tokyo in the Sagami Bay, Japan. The three-dimensional wave fields were reconstructed from the stereo images, which were successfully captured from April 2017 until now, by using an open source software WASS (Waves Acquisition Stereo System). The significant wave heights and periods calculated from the stereo images covering an area of 80 m by 80 m were compared against those derived from the ultra-sonic wave gauge at the tower. Overall, a reasonable agreement is achieved, but the accuracy of the stereo reconstruction degrades with the distance from the camera. Also, the significant wave period derived from stereo imaging tends to be shorter, likely related to the error at high frequencies. The reconstructed wave field will be assimilated into a phase-resolved nonlinear wave model. The ensemble Higher Order Spectral simulations and the implementation of the a4DVAR data assimilation scheme, allowed us to substantially extend the estimated wave field beyond the stereo imaging domain. A field campaign with an ADCP in the field of view of the stereo camera and two surface wave buoys outside of the view were conducted for validation.
Hybrid Renewable Energy Systems Sizing for Offshore Multi-Purpose Platforms
Authors: Recalde Luis , Yue Hong , Leithead William , Anaya-Lara Olimpo , Liu Hongda , You Jiang 
Published: November 2019

Abstract
Integrating marine renewables and aquaculture is a complex task. The generated power of each renewable technology depends on its source cycle (wind, wave, solar PV), leading to periods of zero power production. On the other side, aquaculture farms require smooth and stable power supply since any power shortage can lead to the loss of the entire farm production. This paper illustrates the sizing of a hybrid energy system (wind,solar PV, energy storage) to power up the aquaculture farm. The sizing is based on available commercial technology and the system is mounted on a single multi-purpose platform. Reliability is improved by considering device redundancies. Such hybrid system has not been considered before for aquaculture farms. System rough sizing, based on simple online renewable energy calculators, is used to select existing renewable technologies and HOMER Pro simulation software is used to evaluate the technical and economic feasibility of the microgrid for all possible combinations of the technology selected and perform sensitivity analysis on wind turbine tower height, battery state of charge and solar PV panels reflectance. The optimisation is subject to combined dispatch strategy and net present cost.
On Motion and Hydroelastic Analysis of a Floating Offshore Wind Turbine
Authors: Lamei Azin , Hayatdavoodi Masoud , Wong Carlos , Tang Bin 
Published: November 2019

Abstract
This study is concerned with motion analysis and hydroelastic response of a floating offshore wind turbine to wave loads. The novel floating structure, made of prestressed concrete, is designed to support multiple wind turbines, and it rotates according to the environmental loads to face the incoming wind. The floating structure is attached to a mooring line that allows the rotation of the structure in response to the environmental loads. The floating structure is an equilateral triangular platform. The wind turbines are located at the vertices. Due to the dimensional characteristics of the structure, elasticity of the floating platform plays an important role in its dynamics. While the dynamic response of the structure is driven by both aerodynamic and hydrodynamic loads, this study focuses on the motion and elastic response of the novel floating structure to the hydrodynamic loads only. The three dimensional hydrodynamic loads on the floating structure are obtained by use of the constant panel approach of the Green function method, subject to linear mooring loads. A finite element analysis is carried out for the calculation of the elastic response of the structure. Computations of the integrated linear structure-fluid-structure interaction problem are performed in frequency domain using HYDRAN, a computer program written for the linear dynamic analysis of rigid and flexible bodies. Results presented here include the response amplitude operators of both the rigid and flexible bodies to incoming waves of various frequencies and directions. Also presented are the wave-induced stresses on the floating body, and the elastic deformations.