bluuebunny/crossref_metadata_2025 huggingface dataset:
Computational Prototyping Methods to Design Human Centered Products of High and Low Level Human Interactions
Authors: Ahmed Salman , Irshad Lukman , Demirel H. Onan
Published: November 2019

Incorporating human factors engineering guidelines early in design has the potential to reduce the cost and product lead-time to market. Also, products that go through strict ergonomics assessments are associated with better comfort and safety ratings. However, designers are often caught in the dilemma of what prototyping method to use when assessing product ergonomics early in design. This is especially problematic during the conceptual design phase before the physical prototypes are available or built. In this research, we explore the computational prototyping dilemma for early design ergonomics assessments from both fidelity and human-product interaction perspectives. In this paper, three computational prototypes with different fidelity levels (low, medium-, and high-fidelity) are compared in their adequacy for evaluating designs that comprise low- to high-levels of human-product interactions. We used three computational prototyping strategies: (1) Method #1 is a low-fidelity methodology based a digital sketchpad tool; (2) Method #2 is a medium-fidelity methodology consisted of computer-aided design and digital human modeling; and, (3) Method #3 is a high-fidelity methodology composed of computer-aided design, digital human modeling, and surrogate modeling. In order to perform computational ergonomics analyses using above approach, we selected a generic wall mounted cabinet design and a simplified Boeing 767 cockpit model as case studies to illustrate designs that require low- and high-levels of human-product interactions. Our preliminary results show that low-, medium- and high-level prototyping strategies produce similar ergonomics outcomes when evaluating low-level human-computer interaction (e.g., cabinet model). On the other hand, both low- and medium-fidelity (Method #1 and Method #2) prototyping strategies are limited in terms of providing detailed information about human performance when compared to high-fidelity prototyping (Method #3) in evaluating designs with high-level human-computer interaction (e.g., cockpit model).
A Wizard-of-Oz Experiment to Demonstrate Water Reduction and User Training With an “Autonomous” Faucet
Authors: Jou William , Beaulieu Samantha M. , Lim Adrienne K. , MacDonald Erin F.
Published: November 2019

Resource-conserving products and commercial smart products abound in the market, but the intersection of the two is largely unexplored from the human-centered-design community. Research has shown that people (users) have different cognitive styles that influence their methods of approaching challenges and how they interpret the world. Utilizing this knowledge of cognitive styles, energy conserving products could (1) reduce resource consumption of its users and (2) increase user satisfaction with interacting with those products. Passive products — such as a flow-limiting showerhead — do not seek to change the user behavior and solely change the behavior of the product to conserve water. In this work, we design and test an “active smart” product to see if it can change users through product interaction. A custom faucet was designed and built to conduct an experiment with the Wizard of Oz (WoZ) technique of remotely operating a device to create the impression of autonomy/smartness. Participants were asked to wash multiple sets of dishes to test if: (1) participants use less water when washing dishes with a smart faucet and (2) participants remember this behavior change and use less water in a alter interaction with a normal faucet. Results confirmed the hypotheses and showed that those interacting with the faucet reduced their consumption by 26.5% during WoZ treatment and, importantly, 10.9% while washing after interacting with the WoZ treatment. Limitations include the implementation of the smart algorithm and the willingness-to-pay for a smart faucet in the home. This study demonstrates that smart products can conserve resources and train for further conservation even when the user is not using the smart product.
Numerical Investigations on Dynamic Stall of a Pitching-Lagging Motion Airfoil Under Unsteady Freestream
Authors: Xie Kai , Abbas Laith K. , Chen Dongyang , Yang Fufeng , Rui Xiaoting
Published: November 2019

Lift coefficients of a pitching-lagging SC1095 airfoil with different phase differences and amplitudes under Re = 3.92 × 106 are investigated using computational fluid dynamics (CFD). A simulation results based on overset grid technology and k–ω shear stress transport (SST) turbulence model agrees with experimental results. Dynamic stall is associated with Leading Edge Vortex formation (LEV). The formation process during dynamic stall is shown using pressure superimposed with flow streamlines and dimensionless vorticity field contour. Five cases of phase difference between freestream velocity and lagging motion, φ = 0, 1/4π, 1/2π, π and three cases of amplitudes of lagging motion, hamp = 0.3m, 0.5m, 0.7m, are compared, which showed a regular effect on the lift coefficient loops.
Stiffness Based Stability Enhancement in Human-Robot Collaboration
Authors: Jujjavarapu Sri Sadhan , Esfahani Ehsan T.
Published: November 2019

This paper presents the importance of endpoint stiffness and its role in improving the interaction stability of a human-robot collaborative task. A low effort collaborative task is simulated with the help of an admittance controlled robot. The performance of this robot for different levels of grasp stiffness are compared and a solution in the form of a Variable Stiffness Mechanism is provided. This mechanism provides an opportunity to modify the stiffness at the port of interaction based on two measures, an instability index in the frequency domain, and human muscle contraction in the time domain. Experimental results show an improvement in the performance and stability for the system with high stiffness vs low stiffness. Human muscle contraction provides a time instant at which the stiffness has to be modified and the instability index value provides information about the direction in which the stiffness has to be modified.
HDI Tribology Challenges and Strategies of Heat Assisted Magnetic Recording Drives
Authors: Zhang Youfeng , Yoon Yeoungchin , Xiong Shaomin
Published: November 2019

The key features for Heat Assisted Magnetic Recording (HAMR) head-disk interface (HDI) are higher temperature, rougher media grains and harder disk properties. As a result of these features, it is critical for HDI especially the head to remain wear resistance, contamination robustness and chemical stability as much as possible compared to the current Perpendicular Magnetic Recording (PMR) technology. This work summarizes new tribology challenges and strategies at the HDI arisen from the HAMR technology, in terms of disk carbon overcoats, lubricants, head overcoats and mechanical design.
Real Time Cementing Hydraulics Simulations Bring Risk Down
Authors: Pelipenko Sviatoslav , Flamant Nicolas C. , Impey Simon C.
Published: November 2019

Proper control of downhole pressure during cementing operations is critical to maintaining well integrity, i.e. avoiding getting a well kick or fracturing the formation. Contrary to drilling operations where pressure can be monitored in real time thanks to measurement while drilling by downhole tools, no such measurements are available while cementing. Cementing operations must therefore rely on the use of simulations to estimate pressures downhole and ensure that the well integrity is not compromised. These simulations are typically performed ahead of the operations, but for critical wells it is paramount to also perform the calculations in real time to account for any deviation from the plan.

We will first provide a description of the hydraulics simulator used for real time simulations. A key feature is the ability to account for fluctuations in injected fluid density, as a result of the cement slurry mixing process. This effectively results in tracking a high number of fluids with different density properties. The simulator also takes into account fluid compressibility and pressure and temperature dependent fluid viscosity, the magnitude of the effects of which we examine in application to generic field cases. Another salient feature of the simulator is its ability to determine whether fluid is lost to the formation by using flow returning from the well as an additional input.

We highlight the work accomplished to achieve the performance required for real time computations and then illustrate how the simulator gets used during operation through a case study.
Numerical Simulation of Ice-Wave Interaction by Coupling DEM-CFD
Authors: Lu Teng-Chao , Zou Zao-Jian
Published: November 2019

The motions of ice floes in linear waves were simulated by coupling Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD). The interactions between ice floes are investigated by DEM. The hydrodynamics of ice floes, mainly including the drag force and the buoyancy, are calculated by CFD. In the simulation, the ice floes are treated as discrete elements, and the contact forces between ice floes are determined by the Hertz-Mindlin (no-slip) contact model. The shape of ice floes is an approximate square composed of a number of spherical faces, which can reduce the computation cost. The waves are treated as First Order Airy wave, which is linear in nature and applied to small amplitude waves in shallow liquid depth ranges. The volume of fluid (VOF) method was adopted to capture the free surface. The simulation results are in agreement with the actual situation to a certain extent.
Hydroelastic Analysis and Validation of an End-Anchored Floating Bridge Under Wave and Current Loads
Authors: Xiang Xu , Løken Arne
Published: November 2019

Analysis tools used by the offshore industry are applied for prediction of global dynamic behaviour of the extreme floating bridge concepts being evaluated by the Norwegian Public Roads Administration (NPRA). Validation and code-code comparison of these analysis tools are of significant importance when they are applied to such new and non-traditional structures. The current paper focus on validation between numerical modelling and model tests. An end-anchored floating bridge of around 850m length is studied. A hydro-elastic global analysis model was created by considering the bridge as large radiation/diffracting floaters connected by elastic beams. The analysis has been done both in frequency and time domain, by including the hydrodynamic interaction between the pontoons or not. A systematic check of different parameters that may have impact on the analysis was carried out. The numerical results have been compared with the model tests carried out in MARINTEK (1990). The work provides validation of the current analysis tools and guidelines for future work.
A Voyage Planning Tool for Arctic Transit of Cargo Ships
Authors: Li Zhiyuan , Ringsberg Jonas W. , Rita Francisco Afonso
Published: November 2019

The paper presents a decision-support tool for maritime operations in Arctic seas. This tool targets at improving the safety and fuel efficiency of existing and future cargo vessels that are designed to operate in Arctic and in open water conditions. It is achieved by smart voyage planning using meteorological, oceanographic and ice forecasting.

A single-objective optimization for minimizing the fuel consumption in various scenarios of Arctic transits is established, with the transit time and the safety as the two major constraints. The tool is implemented in an in-house Matlab code, which is based on Dijkstra’s algorithm, a grid-based approach that aims at finding the most cost-efficient path connecting any chosen nodes in a given grid. Results from case studies along the Northern Sea Route indicate that the tool generates appropriate routes in ice-infested Arctic waters. The fuel consumption accounting for ice-induced extra resistance is optimized and the risk of collision with icebergs has been considered.
Including the Impact of Climate Change in Offshore and Onshore Metocean Design Criteria to Ensure Asset Robustness
Authors: Brown Alison , Stephens Ag , Rabb Ben , Connell Richenda , Upton Jon
Published: November 2019

While a significant amount of attention surrounding climate change has focused on mitigation of the causes, there is growing interest and need to adapt to physical climate change impacts which are already being experienced and in anticipation of future changes. Changes in climate have the potential to create hazards in the oil and gas sector although vulnerabilities to these changes are often specific to asset types. Preparedness for climate change can help to reduce damaging effects from acute as well as chronic climate changes. This paper focuses on a simple approach developed to ensure that climate change is included in engineering design, by considering climate change risk and the uncertainty inherent in future projections of climate change into design requirements. It involves using the best available climate change data and an understanding of the relationships between asset performance and environmental (climate-related) conditions. The risk level associated with climate change for a specific asset is determined by consideration of the severity and confidence level of the climate change hazard, the exposure of the asset to the hazard, the vulnerability of the exposed asset to the hazard and the capacity of the asset to adapt to the hazard. The method considers the risk levels, the selection of climate model data, the ‘natural variability’ baseline period to be applied to the climate change data, the climate change model validation, the asset life time and specifically how to modify metocean design criteria to account for climate change to ensure both the ‘start of life’ criteria (typically derived from observed and hindcast data) and ‘end of life’ criteria (including an estimate for the impact of climate change at the end of the asset life) meet the required annual probability of exceedance.
Numerical Modelling of Wave Resonance in a Narrow Gap Between Two Floating Bodies in Close Proximity Using a Hybrid Model
Authors: Yan S. , Ma Q. W. , Wang Junxian , Wang Jinghua
Published: November 2019

This paper presents a numerical investigation on the wave resonance in a narrow gap between two floating bodies in close proximity using a hybrid model, qaleFOAM, which combines a two-phase Navier-Stokes model (NS) and the fully nonlinear potential theory (FNPT) using a spatially hierarchical approach. The former governs the computational domain near the floating bodies and the gap, where the viscous effects are significant, and is solved by using OpenFOAM/InterDyMFoam. The latter covers the rest of the domain and solved by using the Quasi Lagrangian Eulerian Finite Element Method (QALE-FEM). The model is validated by comparing its numerical predictions with experimental data in the cases with linear incident waves. Systematic investigations using incident waves with different steepness are then followed to explore the nonlinear effects on the wave resonance.
Calculation of the Dynamic Positioning Capability of an Offshore Wind Farm Vessel During the Jack-Up Process in the Early Design Stage
Authors: Liebert Maximilian
Published: November 2019

As a consequence of the planned exit from fossil-based energy in the European Union the exploitation of renewable energies has become a major aspect of the Offshore Industry. Especially the construction and operation of offshore wind energy turbines pose a challenge which is met by the use of jack-up vessels with extendible legs. In order to dimension the vessel’s manoeuvring devices in the early design stage and to ensure a safe jack-up process for given environmental loads the dynamic positioning capability during the jacking including the influence of the legs has to be calculated. As part of the development of a holistic dynamic analysis this paper presents the implementation of the legs’ influence in an existing manoeuvring method. The manoeuvring method solves the equations of motion in three degrees of freedom (surge, sway, yaw). It is based on a force model which comprises various modular components. Therefore another component for the leg-forces is added. A Morison approach is chosen to calculate the hydrodynamic forces on the cylindrical legs. The legs’ hydrodynamic added masses are accounted for and added to the hull’s inertial terms. The benefit of the presented method is the possibility to calculate the dynamic positioning capability with extended legs without being dependent on the results of either time-consuming or non-specific model tests. Therefore the method represents a fast computing tool to design the vessel for the specific environmental conditions of the site of operation.
The Impact of Climate Change on the Long-Term Response of Offshore Structures: A Study Case
Authors: Mosquera Irvin Alberto , Sagrilo Luis Volnei Sudati , Videiro Paulo Maurício
Published: November 2019

This paper discusses the influence of the climate change in the long-term response of offshore structures. The case studied is a linear single-degree-of-freedom (SDOF) system under environmental load wave characterized by the JONSWAP spectrum. The wave parameter data used in the analyses were obtained from running the wind wave WaveWatch III with wind field input data derived from two Global Climate Models (GCMs): HadGEM2-ES and MRI-CGCM3 considering historical and future greenhouse emissions scenarios. The study was carried out for two locations: one in the North Atlantic and the other in Brazilian South East Coast.

Environmental contours have been used to estimate the extreme long-term response. The results suggest that climate change would affect the structure response and its impact is highly depend on the structure location, the global climate model and the greenhouse emissions scenario selected.
Qualification of Thermoplastic Composite Pipe Risers: Combined Pressure and Bending Loading
Authors: Bahtui Ali , Kidykas Karl , Richardson Joshua , Wilkins Jonathan
Published: November 2019

In offshore ultra-deepwater oil fields, weight and cost reduction is one of the operators’ top priorities, while maintaining safety and reliability standards. These challenges have made conventional flexible risers a less favourable choice for new construction and replacement projects and have forced asset owners to explore cost saving through innovative technologies such as Thermoplastic Composite Pipe (TCP). Magma Global’s light weight m-pipe® TCP riser and flowline product offers over 40% reduction in installed riser project costs, while bringing exceptional permeation, corrosion, high-temperature and fatigue performance and most importantly long-term reusability benefits. This product is the subject of a thorough qualification program in agreement with the requirements of operators and independent verification agents (IVA) to demonstrate the product’s safety and reliability to asset owners and local regulatory bodies.

This paper presents recent developments on the qualification campaign of m-pipe® TCP for riser applications, with a focus on combined pressure and bending tests designed to verify the pipe strength and stiffness. It addresses the product’s ability to withstand loading in the riser touch-down region of a Free Hanging Catenary (FHC). The qualification process of sample manufacture, rig setup, instrumentation & testing, design model development and validation is presented. Burst load cases and combined bend & burst load cases are tested on m-pipe® and results are compared against design model predictions. We hope the paper will be of interest to anyone working in new material development or product qualification in the offshore industry.
Comparison of VOS and ERA-Interim Wave Data
Authors: Vettor Roberto , Guedes Soares C.
Published: November 2019

Accuracy of Voluntary Observing Ship’s reports is evaluated by a one-to-one comparison with ERA-interim database, specifically considering significant wave height. A first screening allows to detect the most common and undeniable mistakes, as for instance clear errors in reporting the position of the vessel, and delete these observations. Moreover, previous literature is considered to remove systematic biases. Then each report is matched with the appropriate numerical data in terms of location and time, in order to evaluate the scattering of the data, to identify the outliers, and to further prune the database. The procedure allows not only to maintain a database clean from clearly wrong information, which can compromise the statistics, but also to recognize areas and conditions in which the mismatch between numerical data and observations is critical, eventually speculating on the motivations.
Comparison of Temporal and Spatial Statistics of Nonlinear Waves
Authors: Bitner-Gregersen Elzbieta M. , Gramstad Odin
Published: November 2019

In the past, it was most common to derive wave parameters and their statistics from time series of wave elevation. The duration of the wave records has been usually restricted to 20 or 30 minutes. Recently, increasing attention has started to be given to spatial wave data and wave statistics, particularly due to introduction in oceanography of stereo camera systems for collecting space–time ensemble of sea surface elevation. Using numerical linear, 2nd and 3rd order simulations this study compares temporal and spatial statistics of wave parameters. The 3rd order wave data are simulated by a numerical solver based on the Higher Order Spectral Method (HOSM) which includes the leading order nonlinear dynamical effects, accounting for the effect of modulational instability. The Pierson-Moskowitz and the JONSWAP spectrum with different gamma parameters are used in the analysis. Sea states with wave steepness where rogue waves were recorded in nature are considered. Consequences of using temporal contra spatial statistics are discussed in perspective of marine structures’ design. Functional dependency between wave parameters characterizing occurrence of rogue waves in unidirectional wave field is proposed.
Simplifying Methods for Fatigue Analysis of Risers
Authors: Pereira Luiz O. C. M. , Videiro Paulo M. , Sagrilo Luís V. S.
Published: November 2019

This work presents methods for reducing computational costs to estimate fatigue damage in riser structures by simplifying the sea state matrix to be solved in time domain by finite element analyses. Two different methods are proposed: The Equivalent Damage Method (EDM), which is a lump block method with an innovative formulation using vessel linearized response to determine significant sea states; and the Response Surface Method (RSM), which uses results from a few sea states to estimate results for other intermediary scenarios required for the fatigue analysis. Basic assumptions and guidance on how to apply the proposed methods are explained through the text.

The methods are used to solve an example of a Steel Catenary Riser (SCR) connected to a Semi-Submersible vessel, resulting in a reduction of almost 80% of the required computing time. Results show accurate values for damage estimates at the top of the riser, and limitations at the touch down zone. Advantages and disadvantages of each method are discussed in detail, demonstrating that they can be used with discretion at early design stages to estimate fatigue damage of risers, umbilicals and mooring lines in general.
Development and Validation of CFD Analysis Procedure for Predicting Wind Load on Commercial Ships
Authors: Lee Sang-Hun , Kim Sei-Hwan , Kim Deok-Su , Lee Young-Bum
Published: November 2019

This paper describes a numerical procedure for the prediction of the wind load on various types of commercial ships, such as LNGC, oil tanker and container ship. As the size of vessels increases, wind load is playing a more important role when sailing in an open sea and mooring at harbors. To estimate wind load, 3D steady RANS CFD simulation is performed and validated with experimental results obtained from wind tunnel tests. The effect of turbulence source is studied to maintain the turbulence intensity profile at the test section of the wind tunnel and the boundary layer mesh is also investigated to improve the accuracy. The discrepancy in force and moment coefficients between CFD results and wind tunnel tests is reduced and the comparison results show good agreements.
Motion and Load Prediction of Floating Platform in South China Sea Using Deep Learning and Prototype Monitoring Information
Authors: Yao Ji , Wu Wen-hua , Zhao Zi-shu
Published: November 2019

The offshore floating platform shows the strong nonlinear characteristics subject to harsh ocean environmental conditions. It is of practical significance and engineering value to predict the marine environmental load and platform motion response by using the prototype monitoring information. Meanwhile, under the interaction of the high-frequency six degrees of freedom (DOF) movements of the platform.

Based on the long-term prototype monitoring data of a semi-submersible platform in the South China Sea, the present paper mainly studies the following two aspects:

1.The prediction of ocean environmental load considering time correlation is studied based on the method of long-short-term memory (LSTM) neural network with the combination of the field monitoring data. The comparison between predicted and measured results shows that the present prediction method has the high accuracy and low computation cost. Besides, this method can be extended to short-term predictions of other environmental loads.

2.The nonlinear mapping relationship between the ocean environment load and the floater motions is constructed based on the deep learning method. The simulated results indicated that the mapping relationship can be used to predict the six DOFs motions of the platform with high accuracy by using the forecasting prototype monitoring data and ocean weather information. Based on this research and the short-term prediction of environmental loads, we can do some studies on short-term prediction of floater motions in the future.
UHB Design Approach for Multiple Pipelines Installed in Shared Trench
Authors: Liu M. , Cross C.
Published: November 2019

Upheaval buckling (UHB) mitigation for trenched and buried pipelines can constitute a substantial cost element for offshore field development. There appears to have a variety of reasons for dual or more pipelines and umbilicals to be considered for installation inside the same trench. A single shared trench has been used for multiple pipelines not only for cost saving, but especially when constrained and driven by route corridor challenges. The common practice for dual pipeline trenching and UHB design is to either perform UHB design independently without due consideration of the pipelines in the proximity, potentially resulting in a compromised UHB mitigation design, or simply combine the uplift resistance required for each individual pipeline in the proximity to obtain the overall backfill/rock dumping to account for pipeline interactions.

This paper re-examines the rationale of the normal practice and some fundamental aspects of UHB design for dual pipelines installation inside the same trench. The proximity effect on the uplift resistance is investigated with respect to pipeline spacing and burial depth. Its impact on the UHB mitigation is considered by a detailed analysis and a series of parametric simulations with respect to pipeline dimensions and gaps. The sensitivity of the soil slip failure angle and the dilatancy is also performed.

Based on the theoretical analysis and FEA modelling, a model solution is formulated and proposed for evaluating uplift resistance reduction for multiple lines. The formulae are extended to deal with multi-layered soil and rockdump. A number of pipeline configurations have been discussed including a piggyback arrangement. A robust UHB mitigation and reduced optimum rockdumping can be achieved by considering the proximity effect through challenging the industry norms and common approach.
Recent Developments and Challenges of Cleavage Fracture Modelling in Steels: Aspects on Microstructural Mechanics and Local Approach Methods
Authors: Jiang Quanxin , Bertolo V. M. , Popovich V. A. , Walters Carey L.
Published: November 2019

Offshore activity in low-temperature areas requires the use of analysis methods that are capable of reliably predicting cleavage (brittle) fracture of ferritic steels in order to guarantee the structural integrity during service. Cleavage fracture is controlled by physical events at different size scales and is influenced by the multiple microstructural parameters of the material. The prediction of fracture toughness of steels based on the microstructure has received great attention, and relevant techniques have been continuously developed. This paper is aimed at reviewing the recent development of cleavage fracture modelling in steels and identifying the existing challenges to inspire further research. The paper contains three parts aimed at explaining how methods are developed and utilized to predict fracture toughness of steel from its microstructures. (1) The complex multiparametric nature of the microstructures of ferritic steels and its influence on cleavage fracture is introduced. (2) A review is given on the main perspectives and models in micromechanisms of cleavage fracture in steels. (3) Discussion is contributed to the link between micromechanisms and the local approach in cleavage fracture modelling. As a result, the paper gives a state of the art on microstructural mechanics and local approach methods of cleavage fracture modelling in structural steels.
Tethered BOP Stacks: Performance and Monitoring
Authors: Killbourn Stuart , Kebadze Elizbar B. , Maher James
Published: November 2019

Subsea wells present challenges for fatigue utilisation throughout the life of these high-value assets. New wells may be constructed at seabed locations where soil properties may be unfavourable or uncertain. Existing wells may require workover and eventual abandonment. This can lead to relatively small conductors supporting higher BOP masses than was envisaged when these wells were constructed. To address such stability issues during drilling and work-over operations, a BOP stack may be tethered to seabed anchors to provide lateral retention. The increased foundation stiffness raises the BOP characteristic frequency which suppresses motion of the BOP and significantly reduces fatigue of the conductor and wellhead. Real-time monitoring of the tether tensions and BOP characteristic frequency provide on-going verification of the efficacy of this fatigue suppressing technology as well as tracking structural integrity. For example, the ability of the monitoring system to detect loss of tether tension and the success of ROV intervention to reapply tension is demonstrated.
Numerical Study on Vortex Induced Motion of Circular Cylinder With Low Aspect Ratio in Currents
Authors: He Jiawei , Wan Decheng
Published: November 2019

This paper presents the investigation results of the VIM phenomenon, discloses the characteristics of the relative motions of a floating cylinder. Floating circular platforms present a large characteristic diameter associated with a large natural period of motions in the horizontal plane. In this paper, the VIM around floating circular cylinders, m* = 1.0, with very low aspect ratio, L/D = 2, as a motivation for better understanding the VIM of Spar platforms.

In order to study vortex induced motions (VIM) response of a circular cylinder, numerical computations are carried out by our in-house VIM solver vim-FOAM-SJTU. In the CFD simulations the cylinder is moored with linear springs to provide a range of reduced velocities. The fluid domain is gridded by an unstructured grid. The boundary layer is modeled with a first boundary layer y+≈2. The focus is on the effect of reduced velocity on the VIM response. Free decay tests and vortex-induced motion (VIM) tests have been built numerically. The Fourier analysis of the motions have been performed in order to explain in figure-eight-type motion trajectory.
Design Optimization of Ship’s Bow Sailing in Kara Sea and Barents Sea
Authors: Liu Jianfei , Feng Guoqing , Ren Huilong , Hu Wenjia , Sun Yuwei
Published: November 2019

Ships performing their missions in the polar regions will inevitably suffer from sea ice collision, which will lead to structural safety problems. Therefore, ships should be designed according to the characteristics of polar sea ice to enable them to navigate safely in the polar regions. Based on the probability density curve of sea ice thickness and the occurrence frequency of sea ices of different sizes of the Kara Sea and the Barents Sea, this paper preliminarily designs ship’s bow sailing in the Kara Sea and the Barents Sea, establishes the ship’s bow-ice collision model and carries out numerical simulation to obtain the stress distribution. Then it optimizes the structure of the parts of the ship’s bow. After the optimization, the bow structure meets the strength requirements and the weight of the ship’s bow is relatively light.
Hydrodynamics Around a Deep-Draft Semi-Submersible With Biomimetic Tubercle Corner Design
Authors: Liang Yibo , Shi Weichao , Tao Longbin
Published: November 2019

Leading-edge tubercles have been investigating widely on the performance of foils in the last decade. In this study, the biomimetic tubercle design has been applied to the corner shape on a deep-draft semi-submersible. A numerical study on flow over a deep-draft semi-submersible (DDS) with a biomimetic tubercle corner shape was carried out to investigate the corner shape effects on the overall hydrodynamics and motion responses. The hydrodynamic performance of the biomimetic tubercle corner is compared with a traditional round corner design platform. It is demonstrated that, as the corner shape design changed, the motion responses alter drastically. In addition, the flow patterns were examined to reveal some insights into fluid physics due to the biomimetic tubercle corner design. The comprehensive numerical results showed that the three-dimensional effect, which causes spanwise flow, can be reduced by a continuous spanwise (column-wise) variation of the shear-layer separation points.
Robust Leakage Modeling for Plug and Abandonment Applications
Authors: Al Ramadan Mustafa , Salehi Saeed , Teodoriu Catalin
Published: November 2019

Oil and gas wells that require to be shut off forever, after depleting their reserves, need to be plugged and abandoned. Plug and Abandonment (P&A) operations induce many arduous challenges worldwide. The aim of P&A is to isolate and prevent fluid leakage in the wellbore in such a way that all fluids are contained in their formation for an undefined time. Failure of P&A in isolating and preventing fluid leakage can jeopardize the well integrity. Cement plugs that are used in this operation play a crucial role in maintaining the well integrity.

Cement is considered as a porous medium that has an ultra-low permeability that can be achieved when some additives are used in the cement slurry to reduce its permeability and pore space. The cement plug may deteriorate with time under harsh downhole conditions, such as high pressure and temperature and exposure to different fluids. Cement plug deterioration will result in increasing the cement permeability or the overall permeability by creating channels or microannuli.

In this study, several scenarios are presented for gas leakage through cement plugs. In these leakage scenarios, the differential pressure across the cement plug was varied. The aim of generating these scenarios is to investigate the current required cement plug length. In each scenario, four different permeability values were used to assess the risk associated with each value. In addition, the cement plug length was varied to investigate how the cement plug length is going to help ensure good well integrity.

The leakage scenarios presented revealed that longer cement plugs have a longer leakage time. In addition, the results show an increase of leakage time as microannulus gap permeability decreases. Differential pressure exerted on the cement plug have a strong effect on the leakage time. To achieve a long term well integrity in P&A phase, an ultra-low permeable cement plug with excellent bonding, longer cement plug, and a lower differential pressure across the cement must be considered.
Learning a Predictionless Resonating Controller for Wave Energy Converters
Authors: Shi Shuo , Patton Ron J. , Abdelrahman Mustafa , Liu Yanhua
Published: November 2019

This article presents a data-efficient learning approach for the complex-conjugate control of a wave energy point absorber. Particularly, the Bayesian Optimization algorithm is adopted for maximizing the extracted energy from sea waves subject to physical constraints. The algorithm learns the optimal coefficients of the causal controller. The simulation model of a Wavestar Wave Energy Converter (WEC) is selected to validate the control strategy for both the regular and irregular waves. The results indicate the efficiency and feasibility of the proposed control system. Less than 20 function evaluations are required to converge towards the optimal performance of each sea state. Additionally, this model-free controller can adapt to variations in the real sea state and be insensitive and robust to the WEC modeling bias.
Influence of Lined Pipe Fabrication on Liner Wrinkling
Authors: Gavriilidis Ilias , Karamanos Spyros A.
Published: November 2019

An economical method to protect offshore pipelines against corrosive ingredients of hydrocarbons is a double-walled (also called “lined” or “bi-metallic”) pipe, in which a thick-walled low-alloy carbon steel (“outer pipe”) is lined internally with a thin layer (“liner pipe”) from a corrosion resistant alloy material. During the deep-water installation, a lined pipe is subjected to severe plastic loading, which may result in detachment of the liner pipe from the outer pipe forming short-wave wrinkles, followed by local buckling. In the current study, alternative lined pipe manufacturing processes are investigated, including elastic, plastic hydraulic and thermo-hydraulic expansion of the outer pipe, for different initial gaps between the two pipes. The problem is solved numerically, accounting for geometric non-linearities, local buckling phenomena and elastic-plastic material behaviour for both the liner and outer pipe. Two types of numerical models are developed, a quasi-two-dimensional model, examining the mechanical bonding between the pipes, and a three-dimensional model, repeating the manufacturing process and investigating its effect on the mechanical behaviour of a lined pipe subjected to monotonic bending. In addition, the influence of initial geometric imperfections on liner pipe buckling is investigated, showing the imperfection sensitivity of the lined pipe bending behaviour, for each fabrication process.
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

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

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

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

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

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.