bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Study on the End Effect and the Effect Due to the Difference in End Shape of the Fluid Force Acting on a Rotating Cylinder in a Uniform Flow
Authors: Suzuki Masahiro , Ikoma Tomoki , Aida Yasuhiro , Rheem Chang-Kyu
Published: October 2021

When investigating the characteristics of the fluid force acting on a rotating cylinder in a flow, three-dimensional effects such as edge shape and walls become a problem.

In this paper, we investigated the fluid force characteristics of the rotating cylinder, as well as the effect of the flow under the end of the cylinder and the shape of the cylinder end in the water tank experiment. There are three types of experimental conditions: No end flow condition, end flow condition, and condition with end plate. There are five disk-shaped end plates with different diameters, and the changes in fluid force are quantitatively summarized for each ratio between the diameter of the cylinder model and the end plate. By generating a flow under the end of the cylinder, the fluid force is significantly reduced compared to the no end flow condition. By attaching the end plate, the fluid force does not decrease even when a flow is generated under the end of the cylinder. The fluid force increases until the ratio DE/D of the diameter D of the cylinder model and the diameter DE of the end plate is around 3, but after that, it shows a constant value.
Ultimate Strength Envelope of a 10,000TEU Container Ship’s Global Hull Girder Subjected to Combined Vertical Bending, Horizontal Bending and Torsion
Authors: Wang Qinghu , Wang Deyu
Published: October 2021

To figure out the ultimate strength picture of the global hull girder of a 10,000TEU container ship subjected to combined vertical bending, horizontal bending and torsion, a simplified global hull girder of the chosen container ship is numerically modeled and a series of large deflection and elastoplastic nonlinear finite element analyses are conducted to obtain the ultimate strength envelope of the chosen container ship’s global hull girder subjected to combined vertical bending, horizontal bending and torsion. Based on the obtained numerical results, the equations that can quantify the ultimate strength envelope of the chosen container ship’s global hull girder subjected to combined loads are developed, which can be referred as one of the most important indexes to measure the safety performance of the chosen container ship under the most extreme loading conditions.
Numerical Investigation on Flow-Induced Vibrations of Circular Sections in Tandem Arrangement Varying Relative Distance
Authors: Peres Leal Aline , Vitor Reis Guilherme Paulo , Trentin Gonçalves Rodolfo , Luis Condino Fujarra André
Published: October 2021

The flow around a circular section has many applications in engineering, specifically in the offshore area, such as platforms, risers, pipelines, etc. These structures, which are submerged in water, are susceptible to flow-induced vibrations (FIV) and might oscillate at unwanted large amplitudes due to currents and waves. The Computational Fluid Dynamics (CFD) is a tool that allows the investigation of different parameters related to the flow and/or to the body. A CFD analysis is important in the initial design stage of riser arrangements, being a way to predict the best relative distance, since the flow around the upstream cylinder may strongly influence the downstream cylinder forces and movements responses, characteristic of wake-induced vibrations (WIV). In this context, this work carried out simulations to initiate numerical investigations about the flow around tandem arrangements and then properly identify characteristics of the fluid model that generate the results obtained in experiments. Two similar rigid circular cylinders in a tandem arrangement were analysed, in the stationary case and in the case allowed to move in two degrees of freedom (2DOF) — transverse and in-flow directions, with mass ratio m* = 10 and no structural damping, ζ = 0%. The computations were performed using OpenFOAM, a CFD open source software, in a two-dimensional flow and, numerical uncertainties studies were conducted to well define the results, presenting the value plus its uncertainty. There were variations of the tandem distances (T = 2D, 3D, 4D, 5.5D and 6D), at Reynolds number Re = 100. These two-dimensional flow simulations at low Re are important at the initial stage of a project, in order to filter the best results and save time for more advanced analysis. A single cylinder in a turbulent flow was also analysed, with m* = 2.52, varying reduced velocity. Analysis were done comparing forces coefficients and amplitudes with the literature, for both upstream and downstream cylinders. The vorticity was investigated, properly identifying vortex shedding pattern. For stationary cylinders, a critical distance of 4D was found, where the forces coefficients increase. For the 2DOF cylinders in laminar flow, the highest amplitude was 1.04D at VR = 7 for the downstream cylinder. When the cylinders are free to move, the initial tandem distance does not interfere the amplitude results of the upstream cylinder when VR > 2, results also found in experiments at high Re, and, that justify the two-dimensional studies in low Reynolds as being the basis of a project.
Fusing Experimental Measurements and ROM Predicted Data for Wind Load Prediction With Extended Kalman Filter
Authors: Xing Xiuqing , Dao My Ha , Zhang Baili , Lou Jing , Tan Wei Siang , Cui Yongdong , Khoo Boo Cheong
Published: October 2021

Wind tunnel test, Computational Fluid Dynamics (CFD) simulation, and Proper Orthogonal Decomposition (POD) based Reduced Order Model (ROM) are used for wind load prediction on a LNG carrier in this project. In order to train the model for high accurate predictions and provide wind load prediction for vessel operations with high confidence level, extended Kalman Filter (EKF) based data assimilation model is developed to fuse the experimental data and the ROM predicted data.

Effects of sensor locations and sensor numbers on the data fusing are studied. Study results indicate that the single point data assimilation can help with sensor positioning and outlier data detection. Based on the standard errors at the sensor points, prediction accuracy with sorted multipoint data assimilation is higher than that with single point data assimilation.
Estimation of Probability of Fatigue Failure on Tubular Joints
Authors: Lokesh N. , Nallayarasu S. , Karunanithi S.
Published: October 2021

Fatigue is generally considered the most critical failure mode in mechanical and structural systems. Due to high-stress concentrations, welded joints represent the most common fatigue crack initiation in steel structures susceptible to fatigue. In India, especially in western offshore, there are about 300 platforms, and 50% of them have reached their design life but still operating due to existing oil and gas reserves. Fatigue prediction in offshore structures is an extremely complicated process involving many factors such as complicated geometry, material, loading, and environment. These uncertainties are modelled as random variables. The assessment of failure probabilities takes a basis to formulate a limit state function for the relevant failure mode and deterioration mechanisms. The fatigue failure assessment based on a simplified probabilistic approach using the application of reliability-based procedures such as the First Order Reliability Method (FORM) is a useful tool. In the simplified fatigue assessment method, the two-parameter Weibull distribution is used to model the long-term distribution of fatigue stresses. Reliability of tubular joint using known fatigue life is an important factor in decision making for life extension of aged platforms. The methodology adopted in this study uses the linear damage accumulation model of Palmgren-Miner, double slope S-N curve, and one-to-one transformation of the probability density functions of long-term stress range and uncertainties to obtain the probability of fatigue failure as a function of the service life from known fatigue life.
Attempt of Early Stuck Detection Using Unsupervised Deep Learning With Probability Mixture Model
Authors: Inoue Tomoya , Nakagawa Yujin , Wada Ryota , Miyoshi Keisuke , Abe Shungo , Kuroda Kouhei , Tamamura Hitoshi , Bilen Hakan
Published: October 2021

The early detection of a stuck pipe during drilling operations is challenging and crucial. Some of the studies on stuck detection have adopted supervised machine learning approaches with ordinal support vector machines or neural networks using datasets for “stuck” and “normal”. However, for early detection before stuck occurs, the application of ordinal supervised machine learning has several concerns, such as limited stuck data, lack of an exact “stuck sign” before it occurs, and the various mechanisms involved in pipe sticking. This study acquires surface drilling data from various wells belonging to several agencies, examines the effectiveness of multiple learning models, and discusses the possibility of the early detection of pipe sticking before it occurs. Unsupervised machine learning using data on the normal activities is a possible advanced method for early stuck detection, which is adopted in this study. In addition, as a countermeasure to another concern that even normal activities involve various operations, we apply unsupervised learning with multiple learning models.
A 2D Navier-Stokes Equations Solver Based on Generalized Harmonic Polynomial Cell Method With Non-Uniform Grid
Authors: Yu Xueying , Shao Yanlin , Fuhrman David R.
Published: October 2021

It is essential for a Navier-Stokes equations solver based on a projection method to be able to solve the resulting Poisson equation accurately and efficiently. In this paper, we present a new 2D Navier-Stokes equation solver based on a recently proposed fourth-order method, namely the generalized harmonic polynomial cell (GHPC) method, as the Poisson equation solver. The GHPC method is a generalization of the 2D HPC method originally developed for the Laplace equation. In the recent development of the HPC method, loss of accuracy on highly stretched or distorted grids has been reported when solving the Laplace equation, while the performance of the GHPC method on non-uniform grids is still not explored and discussed in the literature. Therefore, the local accuracy of the GHPC method is investigated in detail in the present study, which reveals that the GHPC method allows for the use of much larger grid aspect ratio than that for the original HPC method. Global accuracy of the GHPC method on stretched non-uniform girds is also thoroughly analyzed by considering cases with analytical solutions. Obvious advantages of using the GHPC method in terms of accuracy are demonstrated by comparing with a second-order central Finite Difference Method (FDM). The present Navier-Stokes equations solver uses second-order FDMs for the discretization of the diffusion and advection terms, which may be replaced by other higher-order schemes to further improve the accuracy. Meanwhile, an immersed boundary method [1] is used to study the fluid-structure-interaction problems. The Taylor-Green vortex and flow around a smooth circular cylinder are studied to confirm the accuracy and efficiency of the new 2D Navier-Stokes equation solver. The predictions show good agreements with the experimental and numerical results in the literature.
Focused Plunging Breaking Waves Impact on Cylinder Group in Deep Water
Authors: Cui Ting , Kamath Arun , Wang Weizhi , Yuan Lihao , Han Duanfeng , Bihs Hans
Published: October 2021

The correct estimation of wave loading on a cylinder in a cylinder group under different impact scenarios is essential to determine the structural safety of coastal and offshore structures. This scenario differs from the interaction of waves with a single cylinder but not a lot of studies focus on cylinder groups under different arrangements. In this study, the interaction between plunging breaking waves and cylinder groups in deep water is investigated using the two-phase flow model in REEF3D, an open-source computational fluid dynamics program. The Reynolds-averaged Navier-Stokes equation with the two equation k–Ω turbulence model is adopted to resolve the numerical wave tank, with free surface calculated using the level set method. In this study, focused waves in deep water were modeled with a fixed wave steepness method. Wave breaking occurs when the steepness of the wave crest front satisfies the breaking criteria. The model is validated by comparing the numerical wave forces and free surface elevation with measurements from experiments. The computational results show fairly good agreement with experimental data for both free surface elevation and wave forces. Four cases are simulated to investigate the interaction of breaking waves with a cylinder group with different relative distance, number of cylinders and arrangement. Results show that breaking wave forces on the upstream cylinder are smaller than on a single cylinder with a relative distance of one cylinder diameter. The wave forces on cylinders in the pile group are effected by the relative distance between cylinders. The staggered arrangement has a significant influence on the wave forces on the first and second cylinder. The interaction inside a cylinder group mostly happens between the neighbouring cylinders. These interactions are also effected by the relative distance and the numbers of the neighbouring cylinders.
Research on Kick Detection Model Based on Machine Learning
Authors: Song Xianzhi , Duan Shiming , Pei Zhijun , Zhu Zhaopeng
Published: October 2021

With the expansion of oil and gas exploration and the development of complex oil and gas resource areas, the probability of risk is increasing. Kick is one of the high-risk risks of drilling, and timely and accurate early warning is increasingly important. Based on the kick generation mechanism, kick characterization parameters are preliminarily selected. According to the characteristics of the data and previous research progress, Random Forest (RF), Support Vector Machine (SVM), Fully Connected Neural Network (FNN), and Long Short-term Memory Neural Network (LSTM) are established using experimental data from Memorial University of Newfoundland. The test results show that the accuracy of the SVM-linear model is 0.952, and the missing alarm, the false alarm rate is only 0.064, 0.035. Also, through the analysis of the kick response time, the lag time of the SVM-linear model is 3.6s, and the comprehensive equivalent time is 23.13, which shows the best performance. This paper lays a good foundation for the establishment of an intelligent kick early warning model.
Drag Coefficient for Porous Screen in a Non-Oscillating Perpendicular to Plane-in Flow
Authors: Bhandiwad M. S. , Nasar T.
Published: October 2021

The flow-through porous bodies/structure is one of the more advanced research in the area of energy dissipation in coastal and civil engineering fields. The experiments on the determination of drag coefficient of screens with varying porosities and for the range of flow velocities lead to explore damping ratio in a typical fluid-structure interaction problem. An experimental study has been carried out to assess the drag coefficient of the porous screens as suggested by Keulegan, G. H (1968) [3]. Six different screens with porosities of 4.4%, 6.8%, 9.2% 15%, 20% and 25% are considered. In the experiments, water with a known head from one tank is allowed to flow through a pipe equipped with porous screens into the other tank. Based on the experimental observation, the correlation between Reynolds number and drag coefficient is obtained for all porous screens. The effect of damping nature (damping ratio) of the screen for a particular range of Reynolds number has been explored. As the Reynolds number increases, the drag coefficient decreases with increasing the porosity of the screen. Further, it is understood that the value of the damping ratio decreases with an increasing relative head (H/L).
CFD Simulation of Nonlinear Deep-Water Wave Instabilities Involving Wave Breaking
Authors: Li Yuzhu , Fuhrman David R.
Published: October 2021

Extreme waves at the sea surface can have severe impacts on marine structures. One of the theoretical mechanisms leading to extreme waves is the instability of deep-water wave trains subject to initially small perturbations, which then grow exponentially. The present study focuses on the two-dimensional Benjamin–Feir (or modulational) instability and the three-dimensional crescent (or horseshoe) waves, also known as Class I and Class II instabilities, respectively. Numerical studies on Class I and Class II wave instabilities to date have been limited to models founded on potential flow theory, thus they could only properly investigate the process from initial growth of the perturbations to the initial breaking point. The present study conducts numerical simulations to investigate the generation and development of wave instabilities involving the wave breaking process. A CFD model solving Reynolds-averaged Navier-Stokes (RANS) equations coupled with turbulence closure in terms of the anisotropic Reynolds stress model is applied. Wave form evolutions, Fourier amplitudes, and the turbulence beneath the broken waves are investigated.
Research on Nano-Emulsion Relieving Coal Seam Water Block Damage
Authors: Sun Wei , Zhao LongHao , Wang Qian , Liu Yanchi , Zhu Weiping , Yu Guolin , Zhou Fujian
Published: October 2021

Hydraulic fracturing is the most effective reservoirstimulation techniques in the coalbed methane. However, the polymer in the fracturing fluid has a strong effect on the surface of the coal, causing the water lock damage as high as 70% to 90%. It is important to develop an efficient method for releasing coal seam water lock. In this paper, adsorption experiment, SEM, particle size experiment, core flow experiment, wettability and surface tension experiment are used to study the cause of coal seam water lock damage during fracturing and the effect of nano-emulsion on releasing water lock damage in coal seams. Experimental results show that after coal fracturing, the adsorption amount of polymer on the surface of coal is 14.81 mg/g. The large amount of hydrophilic polymer adsorption causes the pore radius of the coal to narrow. And the surface wettability changes from weak hydrophilic to strong hydrophilic, which increase the water lock damage. Compared with conventional slick water, fracturing fluid, the composite of nano-emulsion and fracturing fluid forms mixed micelles, which reduces the polymer adsorption capacity from 14.81 mg/g to 7.42 mg/g. After scanning by electron microscope, it is observed that the surface roughness of the rock sample is restored; The size of the nano-emulsion is about 10nm, and the very small volume can act deep in the pores of the coal seam; After using nano-emulsion, the gas/water interfacial tension is reduced by 45.1mN/m, and the wettability of coal is improved from hydrophilic to neutral, which reduces the capillary pressure in the pores of the coal and reduces the breakthrough pressure of coalbed methane by 11.1KPa; The water lock release rate is as high as 53.09%. The Nano-emulsion is an ideal choice to remove water lock damage.
Nanoemulsion with Controlled Rheology under Different Temperature for Effective Removal of Oil-based Drilling Fluid in Offshore Drilling
Authors: Meng Renzhou , Wang Chengwen , Dong Xiliang , Xiong Chao
Published: October 2021

Oil-based drilling fluid (OBDF) is an important means for offshore drilling, but it would affect the cementing quality. Nanoemulsions shows potential for OBDF removal, but how to prepare nanoemulsion meeting the engineering requirement is lack of good understanding. Moreover, nanoemulsions usually behave badly under low/high temperature, which would restrict the application. Revealing removal mechanisms of nanoemulsion and improving nanoemulsion stability at different temperature are of great significance.

The nanoemulsion could rapidly spread on the wellbore surfaces, cause the adhering OBDF to curl into little droplets, and solubilize the removed OBDF. The removal efficiency can reach more than 98%. Low temperature and higher concentration of dispersed phase both increased the viscosity of nanoemulsions stabilized by surfactants. PEGs can induce the bridging of emulsion droplets at low temperature, leading to significant increase of nanoemulsions viscoelasticity at low temperature (around 5°C). To control the rheological properties of nanoemulsions, a hydrophobic association polymer, HAAP, was proposed. Nanoemulsions containing HAAP does not gel at low temperature (< 15°C). And the viscoelasticity of nanoemulsions increased slightly when the temperature is higher than 70°C because of the thermoassociating behavior of polymer, which can ensure the stability of the nanoemulsions at high temperature.

This paper is helpful to establish a generic route for preparing nanoemulsions with controlled rheological properties under different temperature, which is benefit for their applications in offshore.
Prediction of Pressure Drops in Liquid-Liquid Two-Phase Flow Across Circular Channels
Authors: Khan Zurwa , Tafreshi Reza , Wahid MD Ferdous , Retnanto Albertus
Published: October 2021

Mechanistic models are necessary for understanding and predicting the behavior of liquid-liquid flow for multiple pipe dimensions, mixture properties, and flow patterns. In this paper, a mechanistic model is proposed to calculate pressure drop across circular channels for liquid-liquid two-phase flow. The developed model considers several key aspects of liquid-liquid flow, such as mixed and wavy liquid-liquid interfaces and dispersion within each liquid’s layers. Unique identifiers, such as height, turbulence, and dispersion, are calculated for each phase, using an augmented separated flow model and nonlinear optimization. Comparison of the proposed model with experimental data, comprising of multiple inclination angles and flow patterns, shows accurate predictions for a variety of liquid-liquid flow patterns, including double- and triple-layered flow.
Clustering Applied to Large Sets of Environmental Conditions for Selecting Typical Scenarios for Ship Maneuvering Real-Time Simulations
Authors: Moreno Felipe M. , Tannuri Eduardo A.
Published: October 2021

The methodology described in this paper is used to reduce a large set of combined wind, waves, and currents to a smaller set that still represents well enough the desired site for ship maneuvering simulations. This is achieved by running fast-time simulations for the entire set of environmental conditions and recording the vessel’s drifting time-series while it is controlled by an automatic-pilot based on a line-of-sight algorithm. The cases are then grouped considering how similar the vessel’s drifting time-series are, and one environmental condition is selected to represent each group found by the cluster analysis. The measurement of dissimilarity between the time-series is made by application of Dynamic Time Warping and the Cluster Analysis is made by the combination of Partitioning Around Medoids algorithm and the Silhouette Method. Validation is made by maneuvering simulations made with a Second Deck Officer.
Use of DNVGL-RP-C203 for Determining the Fatigue Capacity of Connectors
Authors: Muff Anthony , Wormsen Anders , Hørte Torfinn , Fjeldstad Arne , Osen Per , Kirkemo Finn , Macdonald Kenneth A. , Reinås Lorents
Published: October 2021

Guidance for determining a S-N based fatigue capacity (safe life design) for preloaded connectors is included in Section 5.4 of the 2019 edition of DNVGL-RP-C203 (C203-2019). This section includes guidance on the finite element model representation, finite element based fatigue analysis and determination of the connector design fatigue capacity by use of one of the following methods: Method 1 by FEA based fatigue analysis, Method 2 by FEA based fatigue analysis and experimental testing and Method 3 by full-scale connector fatigue testing. The FEA based fatigue analysis makes use of Appendix D.2 in C203-2019 (“S-N curves for high strength steel applications for subsea”). Practical use of Section 5.4 is illustrated with a case study of a fatigue tested wellhead profile connector segment test. Further developments of Section 5.4 of C203-2019 are proposed. This included acceptance criteria for use of a segment test to validate the FEA based fatigue analysis of a full-scale preloaded connector.
Limit Load Capacity of Thick-Walled Pipe Loaded by Internal Pressure and Bending
Authors: Selker Ruud , Brugmans Joost , Liu Ping , Sicilia Carlos
Published: October 2021

Internally pressurised pipe behaves differently than externally pressurised pipe. DNVGL-ST-F101 [4], a prevailing standard for the design of submarine pipelines, provides limit-state equations for combined loading that are valid only if the diameter-to-wall-thickness ratio (D/t) is between 15 and 45. A recent study has shown that the results are increasingly conservative for lower values of this ratio if the nett pressure is acting on the pipe’s outside [8], especially if it is below 20.

In this paper, the applicability of the limit-state equations for thick-walled pipe with D/t less than 15 and loaded by a nett internal pressure has been investigated. The first step was a fundamental review of the formulations. Next, the predicted capacities were compared with those estimated using a finite-element (FE) model. The results greatly coincided, which indicates that the conservatism underlying the formulations does not depend on D/t. Hence they can be used for design against local buckling under internal overpressure, too, when the ratio is below 15.
Comparison Between Shrinkage Strain and FEM Thermo-Mechanical Method for Estimation of Welding Induced Residual Stresses
Authors: Bhardwaj Sachin , Ratnayake R. M. Chandima
Published: October 2021

Residual stress estimation in structural integrity procedures plays an important role during the fitness-for-service (FFS) assessment of girth welds. Various FFS codes and standards, such as API 579 and BS 7910, recommend predetermined residual stress profiles based on finite element modeling (FEM) coupled with experimental results. Nonlinearity associated with non-uniform temperature gradients’ distribution during welding can develop residual stress up to the yield strength of the material, in weld shrinkage and plastic zones. Plastic zone size, shape, and locations are critically important in reducing or controlling final distortions, decreasing the residual stress according to length scale, and defining the optimum sequence of the welding process. However, in practice, estimation of finally developed residual stresses is used in structural integrity procedures for determining the FFS of welded joints. Various FEM models employed in its assessment require large computational time in solving the complex thermo-mechanical phenomenon involved in the welding process. Shrinkage strain models have been found to be fast and effective in determining final residual stresses, once the size, location and shape of the plastic zone can be predetermined. This manuscript demonstrates a comparison between the shrinkage strain method and the moving heat source method, based on transient temperature development as a function of time. The results (or findings) reveal a high compromise between FEM thermo mechanical model and shrinkage strain method in determining final residual stresses with later consuming less computational time. The findings provide significantly important feedback to welded joints’ structural integrity assurance practitioners.
What You May Not Know About Pipe Bends
Authors: Selker Ruud , Liu Ping , Sicilia Carlos
Published: October 2021

Pipe bends are peculiar structures. Although the mechanisms that determine their behaviour are not that different from those of initially straight pipe, their relative contribution can be. This is amplified by shorter bend radii and thinner walls. Typical bends used in an offshore environment will have a radius of three to ten times their cross-section diameter and will behave differently than straight pipe of comparable dimensions. This paper aims to identify and quantify the key mechanisms that drive the behaviour of pipe bends in a deep-water environment. Their behaviour has been studied at global and local scales. The behaviour of bends seems not fully understood amongst academia and in the industry. This paper endeavours to demystify some of those peculiar behaviours, for example, why pipe bends tend to straighten during a mill pressure test.
A Model for Ice Heterogeneity Affecting Bending Failure Against An Inclined Structure
Authors: Simakina Aleksandra , Zvyagin Petr , Drepin Mikhail
Published: October 2021

Experiments with model ice are usually carried out for preliminary assessment of ice qualities of designed offshore structures. Despite the fact that properties of model ice across artificial floe are constant, sometimes various experimental results can be explained not only by measurement errors.

The paper describes various positions of breaking points in a number of model experiments with an ice beam flexural failure. To explain the observed effect, the article suggests the hypothesis on heterogeneity of elastic modulus of an ice floe. The article considers a problem of possible influence of the area of heterogeneity on the position of an ice beam breaking point. Thus, the models of a cantilever beam and a plane lying on an elastic foundation with inconstant Young’s modulus are suggested. These models in form of their approximations by finite differences are applied for making numerical simulations in order to investigate the problem.

With the numerically obtained solutions of a cantilever beam and a plane on an elastic foundation with employed inhomogeneity of elastic modulus, the study observed noticeable change in the position of the breaking point when such inhomogeneity occurred close to the contact area.
A Probabilistic High-Pressure Zone Model of Dynamic Ice Structure Interactions and Associated Ice-Induced Vibrations
Authors: Hossain Ridwan , Taylor Rocky , Moro Lorenzo
Published: October 2021

During ice-structure interactions that are dominated by ice compressive failure, the majority of the ice loads are transmitted through localized contact regions known as high-pressure zones (hpzs). This paper presents a probabilistic modelling framework for dynamic ice-structure interaction based on the mechanics of hpzs. Individual hpzs are modelled as a nonlinear spring-damper system where the stiffness is modelled as a function of nominal strain, with the degree of softening depending on the average strain-rate. Both spalling and crushing failure mechanisms were assessed in the context of periodical sinusoidal response. For spall dominated failure, the model structure showed presence of frequency lock-in in the speed range of 100–125mm/s, beyond which the failure was found to be random in nature with lower amplitude of structural response. The amplitude was also found to be significantly influenced by structural parameters with structural damping having the highest contribution. For pure crushing, an estimated equilibrium layer thickness based on theoretical calculations also showed presence of frequency lock-in. The work highlights the importance of understanding the interplay between these mechanisms, as well as the role of ice conditions and structural parameters on the processes that dominate an interaction.
Semantic Search in Offshore Engineering With Linguistics And Neural Processing Pipelines
Authors: Pol Gonçalves Flavio Jaime , de Oliveira Carmo Vinicius Cleves , Toquetti de Melo Vinicius , Cunha Rodrigo da Silva , Santos Ismael H. F. , Barreira Rodrigo Augusto , Cugnasca Carlos Eduardo , Cozman Fabio Gagliardi , Gomi Edson Satoshi
Published: October 2021

This paper presents a computing pipeline architecture for semantic search in the domain of Offshore Engineering. The proposed system combines modules such as document retriever, passage retriever, and answer extractor to produce textual responses to queries in natural language such as: “What FPSO motion is mostly affected by viscous damping?” Such responses are often needed in Offshore Engineering activities, and linguistic techniques such as those based on inverted indexes with a syntactic focus tend to perform poorly. Instead, this research explores semantic techniques that take into account the meaning of words in the domain of Offshore Engineering. This paper describes a Linguistic QA pipeline architecture built that provides a way to retrieve answers instantly from a collection of 13,000 unstructured technical documents about Offshore Engineering, reports the achieved results and future work. This paper also presents additional modules under construction that exploit Neural Networks and ontologies approaches for semantic search in the domain of Offshore Engineering.
Performance Evaluation of Hybrid Thermal-Solvent Injection in a Post-CHOPS Reservoir With Consideration of Wormhole Network
Authors: Zhao Min , Yang Shikai , Yang Daoyong
Published: October 2021

In this paper, techniques have been developed to evaluate performance of thermal, solvents, and hybrid thermal-solvent processes in a post-CHOPS reservoir with consideration of wormhole network. With the experimentally determined properties of injected gases and reservoir fluids, history matching is accomplished for the reservoir geological model conditioned to the fluid and sand production profiles together with pressure. Meanwhile, the wormhole network is characterized with the newly developed pressure-gradient-based (PGB) sand failure criterion. Once the history matching is completed, the calibrated reservoir geological model is then employed to evaluate performance of thermal, solvents, and hybrid thermal-solvent processes under various conditions. It is found that huff-n-puff processes have a very good performance on enhancing oil recovery when wormhole network is fully generated and propagated. Among all solvent-based methods, pure CO2 huff-n-puff process shows a better performance than flue gas, while the addition of alkane solvents leads to a higher oil recovery compared with CO2 only method. Since the addition of C3H8 and n-C4H10 will significantly decrease the heavy oil viscosity and enhance the swelling factor, all hybrid thermal-solvent injection achieves high oil recovery by taking the advantage of both hot steam and solvents injection.
Concept Study for the Floater Type Selection on Floating Offshore Wind Turbines
Authors: Chujo Toshiki , Haneda Ken
Published: October 2021

The FOWTs (Floating Offshore Wind Turbines) projects are spreading, especially in Europe. Some of FOWTs are doing commercial activities, on the other hand, many new concepts of FOWTs are still published in the world. This may mean that there is room for the reduction of the construction cost of the floater, therefore the development of more reasonable design of the floater would give rise to big business opportunities. These new concept of FOWTs are thought to be optimized regarding the safety and economic efficiency, but there are a few studies for the comparison in the safety, economic efficiency, and parameters which effect to them between different types of floater concepts. Therefore, authors carried out the parametric study in terms of the motion in waves and wind and construction cost for the semi-submersible type and the spar type. In this study, 2, 5, 10, 15MW wind turbines are assumed to be installed on the floater, and dimensions of the floater and an inclination angle because of the maximum thrust force are set as constraint conditions. The construction cost is estimated as a product of material weight and unit cost of material. Authors found the solution regarding the relationship between the construction cost and the performance of the FOWTs through this study. the distance between the columns and the lower pontoon breadth were effective parameters to ensure he performance in waves and to reduce the construction cost of semi-submersible floater.
Optimization of Resistance Performance for Inland Twin-Skeg Ship Based on CFD and Surrogate Modeling
Authors: Yan Helei , Feng Baiwei , Zheng Qiang , Li Heng
Published: October 2021

With the increasingly serious energy problems in the world and the introduction of Energy Efficiency Design Index (EEDI) by International Maritime Organization (IMO), the application of energy conservation and emission reduction methods in ships has been paid more and more attention. With the rapid development of computational fluid dynamics (CFD), ship hull form optimization based on CFD has become a hot topic, Inland twin-skeg ship has a relatively complicated hull form, and it has strong theoretical significance and engineering practical value to carry out hull form optimization research on this type of ship. Based on the multidisciplinary comprehensive optimization platform for ship hydrodynamic performance (SHIPMDO-WUT) self-developed by Wuhan University of Technology research institute of multidisciplinary design optimization of ship performance, this paper using the hull surface deformation method based on the radial basis function interpolation to change the hull form and skeg shape of a 3000t inland twin-skeg oil tanker with invisible bulbous bow. And the high-precision CFD calculation software SHIPFLOW was used to predict the resistance of this ship. Finally, combined with CFD surrogate model and optimization algorithm, the ship with excellent resistance performance is obtained and ensuring the ship displacement and the longitudinal position of the buoyancy center are within the range of certain constraints. At last, the optimization results were verified numerically.
Full-Scale In-Situ Four-Point Beam Bending Field Tests on Sea Ice
Authors: Taylor Rocky , Turnbull Ian , Bailey-Dudley Eleanor , Pritchett Rob
Published: October 2021

The flexural strength of ice is not a basic material property, but rather is an estimate of the maximum stress in the outermost fiber of an ice specimen when it fails in bending. Such conditions correspond to a number of important engineering applications, such as interactions between ice and a sloping structure or between ice and ships. Ice flexural strength is therefore highly important for calculating ice pressures and forces of interest for engineering design. While there has been considerable discussion in the literature regarding scale effects related to ice crushing against a vertical structure, scale effects in relation to bending failure have received much less attention. To this end, more flexural strength data for large, full-thickness sea ice beams are needed. To address these data gaps, a field data collection program was carried out in Pistolet Bay, Newfoundland over two field seasons (2017–2018). During this program, large sea ice beams were tested in-situ using a custom four-point bending apparatus, which was comprised of several main subsystems (e.g., the ram loading system, the platen, the ubrackets, and the hydraulic system). The sea ice beams were completely cut free from the ice cover and loaded at four points, such that the center load is parallel, but opposed to, the loads at the ends of the beam. All tests were done in-situ so that no brine drainage took place and the temperature gradient remained consistent. Tests were carried out for several combinations of beam geometry, which were scaled relative to the ice thickness. In addition to flexural strength, during the Pistolet Bay field program, the physical properties of the ice were measured (temperature, salinity, density). In this paper, a description of the field apparatus, test program and results from the full-thickness in-situ four-point beam bending tests are presented, along with a discussion of practical implications and future work.
Pipe Joint Management for Risers and Pipelines
Authors: Mansour Ghiath (Guy)
Published: October 2021

Minimizing the stress concentration factor (SCF) in pipe joint welding subjected to fatigue is a major concern. Machining the joint ends is one way to achieve this. However, this adds cost, time, risk of potential crack starters, and loss of wall thickness which is detrimental for fatigue, strength, and engineering criticality assessment (ECA) in particular. Pipe joint sorting (certain joints in sequence) and end matching (rotating the pipe joints for best fit) are other ways. However, this adds time, costly logistics, risk of errors, and does not guarantee the minimum possible SCF is achieved. In a typical project, more pipe joints are procured than required in order to mitigate contingencies. For pipelines, this overage is typically a percentage of the required number of joints or pipeline length. For risers, typically double the required number of joints is procured where half of the joints is sent offshore for installation and the remaining half is kept onshore for a spare riser. Then, it becomes very important to send for installation the best pipe joints that produce the best (lowest) SCFs out of the entire batch of pipe joints. This requires calculating the SCF for every potential match of any random joints to be welded together, and then choosing the best joints. Performing such calculations by spreadsheet is not feasible considering the tremendous number of required iterations and calculations. A pipe joint management software development is presented herein which accomplishes this task and examples provided to illustrate the benefits.

Note: Selecting pipe joints with the best end measurements, whether ID, OD, OOR, or thickness does not guarantee that the minimum possible SCFs will be achieved since the SCF is a function of all those measurements.
A Novel Power Series Method for the Analysis of an Offshore Mooring Line
Authors: Kakanda Kabutakapua , Han Zhaolong , Yan Bao , Srinil Narakorn , Zhou Dai
Published: October 2021

The mechanics of offshore mooring lines are described by a set of nonlinear equations of motion which have typically been solved through a numerical finite element or finite difference method (FEM or FDM), and through the lumped mass method (LMM). The mooring line nonlinearities are associated with the distributed drag forces depending on the relative velocities of the environmental flow and the structure, as well as the axial dynamic strain-displacement relationship given by the geometric compatibility condition of the flexible mooring line. In this study, a semi analytical-numerical novel approach based on the power series method (PSM) is presented and applied to the analysis of offshore mooring lines for renewable energy and oil and gas applications. This PSM enables the construction of analytical solutions for ordinary and partial differential equations (ODEs and PDEs) by using series of polynomials whose coefficients are determined, depending on initial and boundary conditions. We introduce the mooring spatial response as a vector in the Lagrangian coordinate, whose components are infinite bivariate polynomials. For case studies, a two-dimensional mooring line with fixed-fixed ends and subject to nonlinear drag, buoyancy and gravity forces is considered. The introduced boundary and initial conditions enable the analysis of an equilibrium or steady-state of a catenary-like mooring line configuration with variable slenderness and flexibility. Polynomials’ coefficients computation is performed with the aid of a MATLAB package. Numerical results of mooring line configurations and resultant tensions are presented for deep-water applications, and compared with those obtained from a semi-analytical and finite element model. The PSM applied to the mooring line in the present study is efficient and more computationally robust than traditional numerical methods. The PSM can be directly applied to the dynamic analysis of mooring lines.
The Optimization Design of the Cross-Sectional Layout of an Umbilical Based on the Hybrid Genetic Algorithm
Authors: Yin Xu , Yang Zhixun , Shi Dongyan , Yan Jun , Wang Lifu , Lu Qingzhen , Tian Geng
Published: October 2021

The umbilical which consists of hydraulic tubes, electrical cables and optical cables is a key equipment in the subsea production system. Each components perform different physical properties, so different cross-sections will present different geometrical characteristic, carrying capacities, the cost and the ease of manufacture. Therefore, the cross-sectional layout design of the umbilical is a typical multi-objective optimization problem. A mathematical model of the cross-sectional layout considering geometric and mechanical properties is proposed, and the genetic algorithm is introduced to copy with the optimization model in this paper. A steepest descent operator is embedded into the basic genetic algorithm, while the appropriate fitness function and the selection operator are advanced. The optimization strategy of the cross-sectional layout based on the hybrid genetic algorithm is proposed with the fast convergence and the great probability for global optimization. Finally, the cross-section of an umbilical case is performed to obtain the optimal the cross-sectional layout. The geometric and mechanical performance of results are compared with the initial design, which verify the feasibility of the proposed algorithm.
Deepwater Span Management on a Mobile Seabed
Authors: Ang Sze Yu , Bernardo Arriane Chiara , Peek Ralf , Vedeld Knut , Caruso Mário , Wu Jie
Published: October 2021

This paper describes a multi-pronged continuous improvement effort to manage the spans of a deep-water pipeline, where even without wave action, the currents are strong enough to move sediments, leading to constantly changing spans. The effort includes: (1) using strakes rather than intermediate supports to suppress VIV, since the latter proved not to be a long-term solution, (2) using partial rather than full strake coverage of spans and developing tools to quantify the level of strake coverage that is required, (3) improving estimates of soil stiffness and damping, and tools to handle amplitude-dependent soil stiffness and damping, (4) performing pluck tests of the operating pipeline by pulling it laterally at midspan with the ROV until a weak link connecting the ROV to the pipe breaks, whereupon the resulting motion of the pipe is recorded with accelerometers, (5) developing tools that allow fatigue damage to be estimated and accumulated for every location along the pipeline (6) sponsoring a joint industry program by DNVGL to quantify the effect of seabed proximity and trench effects on VIV. This paper provides an overview of these activities, with emphasis on recent results and new assessment tools and methods developed and their validation covering items (2–4) above.
Integrated Optimization of Principal Dimensions Based on EEDI and Minimum Propulsion Power
Authors: Wang Yanxia , Sun Wenyu , Zhao Qiang
Published: October 2021

An integrated optimization model of EEDI and minimum propulsion power has been established in this paper. EEDI optimization needs to meet IMO requirements for minimum propulsion power. Installed power reduction is one of the most effective way to optimize EEDI, but it will make the installed power lower than IMO requirements. From the view of security, it is not allowed. In order to coordinate the contradiction between the reduction of EEDI and the minimum propulsion power of the ship, this paper is devoted to the development of an effective and efficient EEDI optimization method under the minimum propulsion power constraints of the ship. The evaluation method of the objective function EEDI is a digital pattern of hydrodynamics performance for tanker series developed by the China Ship Science Research Center. In order to illustrate the method, the VLCC is selected as the research object, and Non-dominated Sorting Genetic Algorithms II is selected to optimize the EEDI. The calculation results show that energy efficiency has been optimized about 4%, so the EEDI and minimum propulsion power integrated optimization model are reasonable and effective.