bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Study on Structural Rehabilitation of Severely Damaged I-Beams Using Fibre Reinforced Polymers
Authors: George Jerin Mathew , Kimiaei Mehrdad , Elchalakani Mohamed 
Published: October 2021

Abstract
Fixed and Floating Offshore structures commonly utilize I-beams as structural components withstanding distributed loads on their decks or inside hulls. These structural members get damaged due to the corrosive marine environment leading to a condition in which they need replacement or rehabilitation. Such situations are not desirable as it will incur monetary losses directly with replacement or repair costs and indirectly through operational losses due to shut down for hot repair works. A safe and economical alternative for structural rehabilitation of damaged I-beams is using Fibre Reinforced Polymer (FRP) composites. An experimental investigation on the feasibility of repair of a heavily damaged I-beam using two different types of FRPs is presented. The severe damage in the I-beam was artificially introduced by removing both flanges and the web for 300 mm in the mid-span of 1800 mm long I-beam. Four-point bending tests under static loads were performed until failure of the beam. The first repair was done using carbon fibre reinforced polymers (CFRPs) and the second one utilized glass fibre reinforced polymers (GFRP). The CFRP repaired specimen showed 277% improvement from the damaged state whereas the GFRP repair improved 248% in terms of the ultimate strength. A comparison of the behaviour between CFRP and GFRP repair is also highlighted in the study. Various parameters like stiffness, ductility, load-displacement behaviour and failure modes of these FRP repairs for damaged I-beams are discussed in detail. Overall, the results from the study portray the adequacy of an FRP rehabilitation to reinstate the strength from such structural damages in I-beams.
Experimental and FNPT-RANS Investigations Into Gap-Excitation and Vortex Dynamics in a Rectangular Moonpool Interacting With Focused Waves
Authors: Saincher Shaswat , Gongalla John Wesly , Vineesh P. , Sriram V. 
Published: October 2021

Abstract
Moonpools are designed to provide a calm environment for lowering of equipment from ships. Considerable research effort has been invested towards understanding water column excitation within a moonpool. However, most recent investigations consider regular waves. The nature of interaction between focused waves and a moonpool is not well-understood; the present work strives to fill this research gap. A series of experiments have been carried out in a 22 m long glass flume in the Department of Ocean Engineering at IIT Madras. Two identical cuboidal boxes were affixed with a 0.15 m gap representing a rectangular moonpool. Focused waves based on a constant steepness spectrum were generated in 0.6 m water depth by a piston-type wave-paddle. The focusing point was set at the center of the moonpool and wave-focusing experiments were performed with and without the twin-body. Wave elevation at various locations along the flume was measured using five wave-gauges. Next, the experiments were numerically replicated using the in-house codes IITM-FNPT2D (for inviscid wave generation) and IITM-RANS3D (for fully viscous wave-structure interaction). Gap-excitation at the instant of focusing has been quantified and correlated with focused wave characteristics and with dynamics of spanwise vortices generated at the edges of the moonpool.
Managing Flow Induced Vibration in Subsea Jumpers
Authors: Naik Rakshith , Urthaler Yetzirah , McNeill Scot , Boubenider Rafik 
Published: October 2021

Abstract
Certain subsea jumper design features coupled with operating conditions can lead to Flow Induced Vibration (FIV) of subsea jumpers. Excessive FIV can result in accumulation of allowable fatigue damage prior to the end of jumper service life. For this reason, an extensive FIV management program was instated for a large development in the Gulf of Mexico (GOM) where FIV had been observed.
The program consisted of in-situ measurement, modeling and analysis. Selected well and flowline jumpers were outfitted with subsea instrumentation for dedicated vibration testing. Finite Element (FE) models were developed for each jumper and refined to match the dynamic properties extracted from the measured data. Fatigue analysis was then carried out using the refined FE model and measured response data. If warranted by the analysis results, action was taken to mitigate the deleterious effects of FIV. Details on modeling and data analysis were published in [5]. Herein, we focus on the overall findings and lessons learned over the duration of the program. The following topics from the program are discussed in detail:
1. In-situ vibration measurement
2. Overall vibration trends with flow rate and lack of correlation of FIV to flow intensity (rho-v-squared);
3. Vibration and fatigue performance of flowline jumpers vs. well jumpers
4. Fatigue analysis conservatism
Reliance on screening calculations or predictive FE analysis could lead to overly conservative operational limits or a high degree of fatigue life uncertainty in conditions vulnerable to FIV. It is proposed that in-situ vibration measurements followed by analysis of the measured data in alignment with operating conditions is the best practice to obtain a realistic understanding of subsea jumper integrity to ensure safe and reliable operation of the subsea system.
The findings from the FIV management program provide valuable insight for the subsea industry, particularly in the areas of integrity management of in-service subsea jumpers; in-situ instrumentation and vibration measurements and limitations associated with predictive analysis of jumper FIV. If learnings, such as those discussed here, are fed back into design, analysis and monitoring guidelines for subsea equipment, the understanding and management of FIV could be dramatically enhanced compared to the current industry practice.
Machine Learning Prediction and Reliability Analysis Applied to Subsea Spool and Jumper Design
Authors: Song Mengdi , Gheroufella Massyl , Chartier Paul 
Published: October 2021

Abstract
In subsea pipelines projects, the design of rigid spool and jumper can be a challenging and time-consuming task. The selected spool layout for connecting the pipelines to the subsea structures, including the number of bends and leg lengths, must offer the flexibility to accommodate the pipeline thermal expansion, the pipe-lay target box and misalignments associated with the post-lay survey metrology and spool fabrication. The analysis results are considerably affected by many uncertainties involved. Consequently, a very large amount of calculations is required to assess the full combination of uncertainties and to capture the worst-case scenario.
Rather than applying the deterministic solution, this paper uses machine learning prediction to significantly improve the efficiency of the design process. In addition, thanks to the fast predictive model using machine learning algorithms, the uncertainty quantification and propagation analysis using probabilistic statistical method becomes feasible in terms of CPU time and can be incorporated into the design process to evaluate the reliability of the outputs. The latter allows us to perform a systematic probabilistic design by considering a certain level of acceptance on the probability of failure, for example as per DNVGL design code.
The machine learning predictive modelling and the reliability analysis based upon the probability distribution of the uncertainties are introduced and explained in this paper. Some project examples are shown to highlight the method’s comprehensive nature and efficient characteristics.
Application of Energy Saving Bow Shape in Actual Seas to JBC
Authors: Sakurada Akiko , Tsujimoto Masaru , Yokota Saori 
Published: October 2021

Abstract
Energy Efficiency Design Index (EEDI) entered Phase 2 in 2020. In this situation, ship performance in actual seas is more important than ever.
As an energy saving bow shape in actual seas, the authors are developing a bow shape named “COVE (Concave shape optimized in waves)”. The aim of COVE is to improve performance in waves without deteriorating performance in a calm sea by transformation above the static swell up at the target speed. Since the bow shape is concave above the static swell up, COVE reduces waves reflected forward because the most concave line has a fine triangular shape instead of the blunt shape of the original.
In this paper, COVE is applied to a Capesize bulk carrier, the JBC (Japan Bulk Carrier). The parameters of COVE are examined and the shape is optimized for the JBC. The effect of COVE is validated by tank tests in terms of wave lengths, wave angles, wave heights and ship speeds.
The results clarified the fact that COVE reduces added resistance in waves by approximately 30 % in head waves compared with the original shape. Validity was verified by the radiating wave shape and the side wall wave form recorded by a video camera in the tests.
Adaptive Constraint Handling in Optimization of Complex Structures by Using Machine Learning
Authors: Cai Yuecheng , Jelovica Jasmin 
Published: October 2021

Abstract
Optimization of complex systems requires robust and computationally efficient global search algorithms. Constraints make this a very difficult task, significantly slowing down an algorithm, and can even prevent finding the true Pareto front. This study continues the development of a recently proposed repair approach that exploits infeasible designs to increase computational efficiency of a prominent genetic algorithm, and to find a wider spread of the Pareto front. This paper proposes adaptive and automatized discovery of sensitivity of constraints to variables, i.e. the link, which needed direct designer’s input in the previous version of the repair approach. This is achieved by using machine learning in the form of artificial neural networks (ANN). A surrogate model is afterwards utilized in optimization based on ANN. The proposed approach is used for the recently proposed constraint handling implemented into NSGA-II optimization algorithm. The proposed framework is compared with two other constraint handling methods. The performance is analyzed on a structural optimization of a 178 m long chemical tanker which needs to fulfil class society’s criteria for strength. The results show that the proposed framework is competitive in terms of convergence and spread of the front. This is achieved while discovering the link automatically using ANN, without an input from a user. In addition, computational time is reduced by 60%.
Optimization of Fracturing Parameters in Changning Shale Based on a New Comprehensive Multi-Factor Analysis Method
Authors: Zeng Bo , Liu Jian , Song Yi , Zhou Xiaojin , Guo Xingwu , Zhao Zhiheng , Li Minghui , Zhou Fujian 
Published: October 2021

Abstract
Horizontal well multi-cluster fracturing technology is the most effective technical approach to exploit unconventional reservoirs (such as shale). The hydrocarbon productivity after fracturing often depends on the selection of fracturing location and fracturing parameters. However, these influencing parameters are very diverse and coupled with each other. Numerical simulation methods and laboratory experiment methods are often complicated to reflect the nonlinear relationship. Therefore, this study develops a new multi-factor analysis method based on field data to explore fracturing parameters’ weights that affect the hydrocarbon productivity after fracturing. This method combined the grey correlation method and entropy weight method to establish a combined weight analysis model. This method can comprehensively evaluate the influence factors on the post-fracturing productivity and ensure the accuracy of the obtained results through a field test. In our study, the influence of geological and fracturing parameters on 50 horizontal wells in Changning Shale is analyzed using the new method. These 50 wells are from the same block but have different values of fracturing parameters. The analysis results show that the fracturing parameters’ weight rankings on the post-fracturing productivity are fluid injection intensity, injection sand intensity, cluster spacing, injection rate, stage length, and average pump pressure. The weight rankings of geologic parameters affecting post-fracturing productivity are total gas content, brittle mineral content, porosity, Young’s modulus, minimum principal stress, total organic carbon, Poisson’s ratio, and maximum principal stress. Our study provides a new means of analyzing the influential factors of the in-situ hydraulic fracturing. Also, it gives a helpful guide for the selection of fracturing parameters in Changning Shale.
A Neural Network Time Dependent Hydrodynamic Force Model for Forced Two-Degree-Of-Freedom Sinusoidal Motion of a Circular Cylinder in a Free Stream
Authors: Aktosun Erdem , Xiros Nikolaos I. , Dahl Jason M. 
Published: October 2021

Abstract
A data-driven hydrodynamic force model is developed to model the dynamic forces on an oscillating circular cylinder for flow conditions where Vortex-Induced-Vibrations (VIV) are known to occur. The model is developed for use in future control systems to improve VIV-based energy harvesting. The dynamic model is empirical, utilizing force measurements obtained for a large set of forced motion experiments, spanning a range of parametric values that prescribe the kinematics of the cylinder motion. The model includes the dynamics of a circular cylinder undergoing forced combined in-line and cross-flow motion in a free stream. The experiments were conducted in a fully automated towing tank where parameters of in-line amplitude of motion, cross-flow amplitude of motion, reduced velocity, and phase difference between in-line and cross-flow motion were varied over nearly 10,000 experiments. All experiments were carried out at a constant Reynolds number of 7620. A feed forward neural network is trained using the force database to develop a time dependent model of forces on the cylinder for given kinematic conditions. Selected outputs of the force model are presented, providing a basis for future synthesis in energy harvesting control applications.
Quasi-Steady Analysis of Impulse Turbine Under Reciprocating Flow
Authors: Yu Yang , Zhao Mingren , Li Zhenmian , Yu Jianxing , Gao Yang , Zhao Yu 
Published: October 2021

Abstract
The impulse turbine, which is a part of an oscillating wave column, plays an indispensable role in wave energy conversion. In this paper, a self-rectifying impulse turbine has been investigated numerically under reciprocating flow and the quasi-steady analysis method of the turbine has been studied. Firstly, the numerical model was validated by corresponding experiment results. Then, the reciprocating flow condition was accurately simulated with the method of setting double velocity inlets. The results showed that there existed hysteretic loops in turbine performance curves. And different pressure drops in acceleration and deceleration led to this hysteretic characteristic. Finally, in order to investigate quasi-steady analysis method, the frequency and amplitude of the reciprocating flow were changed respectively and the results were compared with those of steady flow. It has been found that hysteretic loops are distributed around the curves of steady flow. When the frequency is lower or amplitude is smaller, the results of reciprocating flow are closer to those of steady flow. In conclusion, the performance of steady flow can be used to predict the performance of reciprocating flow with little velocity change in a short time, which reveals the feasibility of quasi-steady analysis method.
Cyclic Response and Instability Analysis of Seabed With Cohesionless Soils Due to Surging Waves
Authors: Rafiei Amin , Gabr M. A. , Rahman M. S. , Ghayoomi Majid 
Published: October 2021

Abstract
Surface waves may generate significant loadings on the seabed destabilizing sediments and the supporting marine structures. This threat is more pronounced in shallower water depths where the cyclic wave loading may induce residual pore water pressure in sediments triggering soil liquefaction. In this paper, a coupled numerical framework is presented to evaluate the interaction of waves and horizontal seabed considering nonlinear cyclic behavior of the cohesionless soil. A simple experimental model is employed for concurrent simulation of nonlinear buildup of pore pressure and deformation of saturated sand subjected to the cyclic loadings. The model (in elemental scale) is incorporated into a finite element code to solve the interaction of wave and seabed. Poro-elastoplastic response of the seabed is obtained by modifying the Biot’s coupled flow-and-deformation equations by adding equivalent nodal force terms associated with residual deformations of the soil. Potential flow theory is adopted for the fluid domain to model wave-induced pressure and flow fields. The governing equations and boundary conditions are solved using finite element analysis in time domain. The numerical framework is verified against results of cyclic triaxial compression tests and analytical solutions. Parametric studies are conducted to evaluate the effects of wave characteristics on triggering the residual liquefaction. The numerical results indicate good agreements with experimental measures. The results also show that for large waves, the progressive buildup of pore pressure in sediments may become high enough, leading to residual liquefaction. The details of the numerical model and the potential of residual liquefaction within the seabed soil are discussed.
Development of Deep Draft Semi-Submersible FPU Hull (Casting-Free) Targets for Oil Field in Gulf of Mexico
Authors: Yuck Raehyoung , Kang Daehoon , Han Ik-seung , Kim Eungsu , Kim Munsung , Shin Ki-young , Park Jong-woo , Kim Tae-min , Kang Sang-gu 
Published: October 2021

Abstract
A deep draft semi-submersible hull has been developed as a standardization concept which can support the topside structures up to the facility weight for the specific level of daily oil production in GOM (Gulf of Mexico).
The designed hull has the optimized dimensions of ring pontoon and four columns for coping with the weight change of topside and the innovated hull shape to eliminate the casting which is normally used at the corner node area where high stress concentrated on. The hull form also has the good global motion in waves, winds and currents to be able to use the SCR (Steel Catenary Riser).
The mooring systems are designed for water depths of 1,500m as a standard design concept of hull including mooring lines (3 × 4). The global performance is validated for the maximum offset, the mooring line tension and the acceleration. The possibility of SCR usage is also investigated with the fully coupled time-domain analysis to confirm that the designed hull form has the suitable hydrodynamic characteristics to permit the minimum vertical motion performance for SCR.
Throughout the global performance and mooring analysis, the designed Semi-FPU fulfills all stability requirements of rules and codes specified in design of basis for both intact and damaged conditions, and has good motion characteristics such as inclination, acceleration, sectional loads and air gap and mooring system compliance with design criteria in the view point of mooring tension, offset and fatigue damage.
Also, the global structural strength analysis has been performed to extract stresses and displacements where local points which are pontoon-column connection areas from the global model. The local points need to reinforce during detail design stage from buckling, yielding and fatigue analysis for normal operating and extreme storm conditions.
URANS Simulations of a Cruise Ship in Crabbing Motion
Authors: Zou Lu , Zou Zao-jian 
Published: October 2021

Abstract
In ship manoeuvrability, the crabbing test is critical to evaluate the hydrodynamic quantities for the guidance of an efficient and safe berthing or unberthing manoeuvres. In the present study, the crabbing performance of a cruise ship is investigated by an unsteady Reynolds-averaged Navier-Stokes (URANS) method considering the instantaneous relative motion between the ship and the quay. In the numerical simulations, the cruise ship is approaching the quay wall at a constant lateral speed. The crabbing motion with five degrees of freedom is modeled by the dynamic overset mesh technique, while the free surface elevation is simulated by the Volume of Fluid method. For reliable predictions of the crabbing performances, the timestep dependency study is conducted and a suitable time step is determined. From the computations, the hydrodynamic performances of the cruise ship, including forces and moments, as well as the surge, sinkage, roll, trim and yaw motions are predicted. The numerical results indicate variations of the hydrodynamic quantities under the impacts of ship speed and blockage effects by the quay wall. The present results can be used to evaluate the crabbing ability of the cruise ship and to provide guidance for estimating and designing the crabbing model test in further investigations.
Settling Behavior of Particles in Bubble Containing Newtonian Fluids: Experimental Study and Model Development
Authors: Jing Silin , Song Xianzhi , Zhu Zhaopeng , Yu Buwen , Duan Shiming 
Published: October 2021

Abstract
Accurate description of cuttings slippage in the gas-liquid phase is of great significance for wellbore cleaning and the control accuracy of bottom hole pressure during MPD. In this study, the wellbore bubble flow environment was simulated by a constant pressure air pump and the transparent wellbore, and the settling characteristics of spherical particles under different gas volume concentrations were recorded and analyzed by highspeed photography. A total of 225 tests were conducted to analyze the influence of particle diameter (1–12mm), particle density (2700–7860kg/m^3), liquid viscosity and bubble volume concentration on particle settling velocity. Gas drag force is defined to quantitatively evaluate the bubble’s resistance to particle slippage. The relationship between bubble drag coefficient and particle Reynolds number is obtained by fitting the experimental results. An explicit settling velocity equation is established by introducing Archimedes number. This explicit equation with an average relative error of only 8.09% can directly predict the terminal settling velocity of the sphere in bubble containing Newtonian fluids. The models for predicting bubble drag coefficient and the terminal settling velocity are valid with particle Reynolds number ranging from 0.05 to 167 and bubble volume concentration ranging from 3.0% to 20.0%. Besides, a trial-and-error procedure and an illustrative example are presented to show how to calculate bubble drag coefficient and settling velocity in bubble containing fluids. The results of this study will provide the theoretical basis for wellbore cleaning and accurate downhole pressure to further improve the performance of MPD in treating gas influx.