bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wave-Current Interactions in a Marine Current Turbine Using ANSYS FLUENT CFD
Authors: Singh Amit , Arockiasamy Madasamy 
Published: October 2015

This paper presents the results of the study on the wavecurrent interactions of an idealized full scale marine current turbine (MCT). A multi-phase flow model is used for simulation of three cases: still water and two different wave heights. The Standard k-ω turbulence model is chosen based on the stability of the pressure and velocity plots upstream and downstream the turbine rotor plane. The three cases are used in the present study to compare the effects of wave height and current velocity on the turbine rotor. The velocity, and pressures on the turbine blades are computed for each case using ANSYS FLUENT CFD Software. The thrust, torque, and power in the MCT are calculated using the results obtained from the CFD simulation.
The turbine rotor blades are drafted in 3D using SolidWorks by extruding cross sections of a 43.2 m diameter turbine blade published by the National Renewable Energy Laboratory (NREL). Tetrahedral mesh elements are used to represent the multiphase fluid domain and rotor blades in ANSYS ICEM CFD due to its simplicity and speed of computation. The ANSYS FLUENT simulation is set up to run air and water phases in the domain, while the rotor blade is suspended in the fluid domain, such that there is 20 m of water in front and 100 m behind the plane of rotation. The effects of varying wave heights on the thrust, torque, and power are presented based on the tip speed ratios. The power generated by the turbine rotor from the wave cases is found to be higher than those for the still water case, at lower current velocities. However, at current velocities higher than 2.00 m/s, the power generated from the still water case is higher than the wave cases. At lower tip speed ratios, the thrust on the turbine, subjected to wave conditions, is lower than that for the still water condition. At higher tip speed ratios, the thrust on the turbine, under wave conditions, is higher than that for the still water condition. The torque decreases exponentially with increases in the tip speed ratio for all three cases, but the torque remains nearly constant with increases in wave height. The results provide detailed information which would be valuable in the design and operation of marine current turbines in wave environments.
Comparison of Numerical Methods for Strain Based ECA
Authors: Navarro Josef , Low Andrew , Tran Thao (Joe) 
Published: October 2015

The integrity of subsea pipe girth welds is routinely ensured through Engineering Criticality Assessments (ECAs) based on fracture mechanics principles. In order to capture the whole design life, the ECA must cover loadings that the pipeline is subjected to during both installation and operation.
Stress based semi-analytical methods using Failure Assessment Diagrams (FAD) have been used extensively for ‘run of the mill’ assessments as far as C-Mn steel pipe with overmatching weld is concerned. These stress based methods are captured in depth in industry codes such as BS7910 and DNV-OS-F101.
In recent years however, with industry seeking to transport more corrosive fluids, the use of pipe containing a corrosion resistant alloy (CRA) layer is becoming increasingly popular. Together with the CRA layer, anti-corrosion weld consumables material would be used at the pipe joints to protect the whole pipeline from corrosion. Some of these weld consumables, especially at high temperature, partially overmatch or even undermatch the parent pipe material, resulting in difficulties in application of conventional FAD approach. Industry has turned to numerical methods to fill in gaps which are not covered by the FAD based approach. However no codified approach/standard exists for executing numerically based ECAs.
This paper attempts to outline the FAD and numerical approaches being used by industry. The different approaches will be assessed for their range of application, limitations of execution and comparison of results obtained. The study is carried out for the case of a typical external surface flaw in a 12″ pipe.
Virtual Spring-Damping System for Flow Induced Motion Experiments
Authors: Sun Hai , Bernitsas Marinos P. , Kim Eun Soo , Bernitsas Michael M. 
Published: October 2015

The research objective of the Marine Renewable Energy Lab (MRELab) is to design multi-cylinder VIVACE Converters and optimize their power output for a broad range of velocities. For a given geometric and mass configuration of a school of cylinders, each point on the power envelope, at a given flow-speed, is a function of the spring constant and damping. Conducting tests with real springs and dampers requires lengthy preparation for each set of experiments. A more efficient way to conduct experiments faster and accurately is developed based on a controller embedded virtual spring-damping system (Vck) that des not include the hydrodynamic force in the closed loop. Each oscillator consists of one Vck, one interchangeable cylinder moving on submerged roller blocks and driven by the fluid flow, and connected to the controller through belts and pulleys. It is designed to achieve the desired static/dynamic friction through the Vck. An Arduino embedded board controls a servomotor with an optical encoder, which enables real-time position/speed measurement. A system identification (SI) methodology is developed making possible to identify the damping model of any oscillator, which is typically much more complicated than the classical linear viscous model. Upon completion of the SI process for an oscillator, the actual nonlinear damping model is subtracted using the controller and leaving the system with zero damping. Then, a mathematically linear damping model is added, thus, resulting in a system with real linear viscous damping. This process enables changing the spring constant and harnessing damping through the controller instantly. Experiments are then conducted with both real spring dampers and Vck to validate the process. All FIM experiments are conducted in the Low Turbulence Free Surface Water Channel of the University of Michigan at 16,000<Re<140,000.
The main findings are: (a) The Vck system was developed keeping the hydrodynamic force out of the control loop and, thus, not biasing the FIM. (b) The agreement between real and virtual springs and dampers was excellent in FIM measurements over the entire range of spring constants and velocities tested. (c) The lag due to the controller was minimal and significantly reduced compared to the first generation of Vck built in the MRELab.
Methodology to Evaluate Sea Ice Loads for Seasonal Operations
Authors: Thijssen Jan , Fuglem Mark 
Published: October 2015

Offshore structures designed for operation in regions where sea ice is present will include a sea ice load component in their environmental loading assessment. Typically ice loads of interest are for 10−2, 10−3 or 10−4 annual probability of exceedance (APE) levels, with appropriate factoring to the required safety level.
The ISO 19906 standard recommends methods to determine global sea ice loads on vertical structures, where crushing is the predominant failure mode. Fitted coefficients are proposed for both Arctic and Sub-Arctic (e.g. Baltic) conditions. With the extreme ice thickness expected at the site of interest, an annual global sea ice load can be derived deterministically. Although the simplicity of the proposed relation provides quick design load estimates, it lacks accuracy because the only dependencies are structure width, ice thickness and provided coefficients; no consideration is given to site-specific sea ice conditions and the corresponding exposure. Additionally, no term is provided for including ice management in the design load basis.
This paper presents a probabilistic methodology to modify the deterministic ISO 19906 relations for determining global and local first-year sea ice loads on vertical structures. The presented methodology is based on the same ice pressure data as presented in ISO 19906, but accounts better for the influence of ice exposure, ice management and site-specific sea ice data. This is especially beneficial for ice load analyses of seasonal operations where exposure to sea ice is limited, and only thinner ice is encountered. Sea ice chart data can provide site-specific model inputs such as ice thickness estimates and partial concentrations, from which corresponding global load exceedance curves are generated. Example scenarios show dependencies of design loads on season length, structural geometry and sea ice conditions. Example results are also provided, showing dependency of design loads on the number of operation days after freeze-up, providing useful information for extending the drilling season of MODUs after freeze-up occurs.
Vessel Performance Analysis and Fuel Management
Authors: Mak Lawrence , Seo Dong Cheol , Kuczora Andrew , Sullivan Michael 
Published: October 2015

A prototype Vessel Performance Monitoring and Analysis System (VPMAS) was deployed on a ferry to acquire needed performance data, to help improve vessel performance and reduce fuel consumption. A paper published in 2014 described preliminary data trends observed, key performance indicators computed, data products explored and exploratory tools developed for crews to gain insight into their vessel operation. The current paper describes further analysis of the operational data for speed optimization in calm sea states and the preliminary development of trim optimization software.
It was found that trip durations around 7 hours (13.3 knots) use the least amount of fuel. The least amount of fuel is used when the excess distance travelled is minimized and the voyage time is optimized. There is a lot of leeway in terms of voyage time and excess distance travel by the ship before there is a heavy penalty on fuel consumption. Considering only a mean draft of 6 m and an average speed of 14 knots in the current paper, the optimal trim condition for the ferry is around −0.6 m (bow down), which reduces the resistance by 15% compared to the even keel condition. Positive trim causes the considerable increase of the total resistance consistently.
Mobile Data Collection
Authors: Lugo David , Ortega Juan 
Published: October 2015

A key process in the oil industry to make decisions is data collection. To improve productivity it is important data and information analysis. For many organizations is not profitable data automation, which has an impact in the way organizations, collect data. Data collection is taken by manual processes that create uncertainty for analysis because it is not reliable. As consequence, making a decision has not the planned results. After working for many years in the oil industry was identified:
1. People collecting data in a manual process normally by using a piece of paper which could be lost or damage.
2. After taking data at the well, data are brought to the office. Then, data are downloaded by another worker in computer software. It can be modified intentionally or not.
3. Accuracy of data collection activity is carried out. How do we know if the staff really went to work area?
4. Training to new staff, lack of experience?
5. There are “risks zones” due vandalism, facilities are damaged by people who stole devices which causes great money losses to companies.
All these mentioned factors affect decision making which has a big impact in the production process. This application helps the whole process from collection data until data are registered in databases.
This application considered several observations, suggestions and comments from people involve in the oil industry, especially at the production area. As a result, it is a tool that support data collection, standardize information in databases, improve data quality (it doesn’t matter localization), shows time and photographic position in a mobile device.
Information is generated digitally taking advantage of easy handling.
To summarize advantages of the whole system:
• Reduce time of the data re-collection process
• Improve data quality
• Reduce amount of people working on data registration
• Data reliability
• Support decisions making
• Minimize the use of paper in order to help ambient environment
• Improve vehicle logistics
• Minimize use of gasoline which helps to reduce costs
• Help to optimize routes for vehicles on the field
• Productivity, Maintenance, etc., reports can be generated
• Vandalism is not a problem
Methods for Establishing Governing Deck Impact Loads in Irregular Waves
Authors: Birknes-Berg Jørn , Johannessen Thomas Berge 
Published: October 2015

As offshore reservoirs are depleted, the seabed may subside. Bottom fixed installations which previously have had sufficient clearance between the deck and the surface may be in a situation where wave impact with the deck must be considered at relevant probability levels. The accurate calculation of deck impact loads with a prescribed probability of occurrence taking into account the relevant properties of the incident waves, presents a considerable challenge.
The ShorTCrest JIP has addressed both the distribution of the crest height in extreme sea states, the properties of the largest crests and the deck impact loading on a closed deck. It has been concluded that the largest waves in the sea may be in the process of breaking and thus have properties which deviate significantly from estimates found from weakly nonlinear irregular or regular wave theory /5/.
The present paper investigates a simple method to calculate deck impact loads in irregular waves which take into account the irregularity of the sea state and the possibility of wave breaking. The method is a two-step approach. Firstly, a long duration simulation of surface elevation is carried out using second-order theory in order to identify possible deck impact events. The individual wave events which are capable of impacting the deck is then reproduced using a CFD method and the distribution of the deck impact loads is established.
The calculations are compared with model test results for wave impact with a large volume deck box in a single steep sea state and with CFD calculations of deck impact with regular waves.
Water Intake Riser Model Test and Numerical Calibration
Authors: Xiang Sherry , Cao Peimin , He Jingxi , Kibbee Steve , Bian Sean 
Published: October 2015

A model test campaign of a large diameter water intake riser (WIR) has been planned, designed, and successfully executed in an offshore model basin. The objective of the model test is to better understand the global dynamic behavior of WIR, and thus advance its design. The scopes of the model test are to measure the response of the riser under floater motions; investigate the effect of the internal water and flow rate; and observe any vortex-induced-vibration (VIV) and axial instability due to motion and / or internal flow.
The paper presents the model test results and the numerical calibrations and validations. The WIR pipe was carefully scaled and designed to meet the test objectives. The WIR in model test scale is 150 mm in inside diameter and approximately 36 m in length. The model test setup includes a fully instrumented riser, a planar motion mechanism (PMM) which simulates the vessel motion and an internal water flow system (IWFS). The riser was instrumented with Fiber Bragg Grating (FBG) strain sensors along the pipe length and circumference. The WIR was hung-off from the PMM inside the deep basin pit. More than 200 cases were carried out in the basin including the sinusoidal motion tests and random motion tests with different flow rates.
The model tests collected a wealth of data of the WIR dynamic responses under the vessel motions and the internal water flow conditions. As expected, WIR global bending responses are highly dependent on the pipe excitation modes and their corresponding mode curvatures. These responses can be predicted well by numerical software through a calibration process. The axial response of WIR due to motion and/or internal flow is much more complex. The amount of internal water coupled with the pipe depends on the vessel motions and internal flow fluctuation. This is important for axial stability prediction and seawater lift system design.
An Experimental Investigation About Fatigue Crack Growth Rate of Aluminum Alloy Considering Various Mean Stress
Authors: Choi Yoo , Kim Deok-Geun , Park Jeong-Yeol , Lee Kyoung-Seok , Lee Jae-Myung , Kim Myung-Hyun 
Published: October 2015

In general, aluminum alloy is a commonly used for liquefied natural gas (LNG) storage systems. In this regard, it is important to know exact mechanical properties at cryogenic temperature. There are many researches to assess mechanical properties of aluminum alloy, such as tensile strength, fatigue performance and fracture toughness. Fatigue crack growth rate (FCGR) is important to predict the service life. In particular, mean stress effect can significantly affect the fatigue life. In this regard, this study carried out by a series of FCGR test at five different stress ratios (R=0.1, 0.3, 0.5, 0.7 and 0.85).
The major objective of this paper is to suggest a new model that can consider the mean stress effect on FCGR of aluminum alloy in a unified manner. A mean stress equation is incorporated into Paris’ law. In order to validate the model, FCGR test data of aluminum alloy is compared with Walker’s relationship. Compared to the other existing model, the new model is found to exhibit more accurate result compared to Walker model.
COER Hydrodynamic Modeling Competition: Modeling the Dynamic Response of a Floating Body Using the WEC-Sim and FAST Simulation Tools
Authors: Lawson Michael , Garzon Braulio Barahona , Wendt Fabian , Yu Yi-Hsiang , Michelen Carlos 
Published: October 2015

The Center for Ocean Energy Research (COER) at the University of Maynooth in Ireland organized a hydrodynamic modeling competition in conjunction with OMAE2015. Researchers were challenged to predict the dynamic response of a floating rigid-body device that was experimentally tested in a series of wave-tank tests. Specifically, COER set up a blind competition, where the device specifications and test conditions were released, but the experimental results were kept private until all competition participants submitted their numerical simulation results.
The National Renewable Energy Laboratory and Sandia National Laboratories entered the competition and modeled the experimental device using both the WEC-Sim and FAST numerical modeling tools. This paper describes the numerical methods used to model the device and presents the numerical modeling results. The numerical results are also compared to the experimental results provided by COER at the completion of the competition.
Numerical Study of Thermosyphon Protection for Frost Heave
Authors: Abdalla Basel , Fan Chengye , McKinnon Colin , Gaffard Vincent 
Published: October 2015

Thaw subsidence and frost heave are two different hazards to pipelines in arctic regions. The former is due to the thawing of permafrost induced by a warm pipeline, while the latter is resulted from a cold buried pipeline that causes ice lens growth upon freezing in the direction of heat loss. Some pipelines may be operated in a wide temperature range and thus subjected to both types of threats.
Two-phase closed thermosyphons have been employed extensively in Arctic projects to protect the permafrost from thawing. The thermosyphons’ response as a “thermo-diode” is the key to this technology. This paper presents a finite element analysis (FEA) based feasibility study for using thermosyphons with pipelines in arctic regions to reduce the potential for frost heave. There are two major challenges in the numerical simulation. One is the efficient modeling of a thermosyphons which works as a heat pump in winter and stops working in summer. This study proposes an anisotropic conduction model that simplifies the thermal-fluid processes within the thermosyphon without overwhelming computational cost. The other challenge is the frost heave modeling, which was recently achieved based on the framework of the porosity rate function. New developments involved in this paper include the extended application to permafrost and transient temperature boundary conditions.
The outcome of this work proves the value of using thermosyphons with pipelines that transfer both cold product. The method introduced here can also be used to optimize the design of new infrastructure and pipelines in permafrost, as well as to assess how thermosyphons work as a mitigation method in existing projects that are affected by frost heave.
Integrated Production Management by Processes: A Case History at the Marine Region
Authors: Flores-Avila Fernando Sebastián , Riaño-Caraza Juan Manuel , Colina-Alvarez Jesús Antonio 
Published: October 2015

As part of its strategic plan 2014–2018 Pemex Exploration and Production (PEP) has decided to modify the organizational structure in order to change from a function based structure to a new one based in process, supported on three fundamental axes: People, Processes and Technology. On this direction, it has been assigned to the Technical Resources Management Vice-presidency the responsibility to implement a strategy that will enable to improve performance into the Assets of the Marine Region. This paper presents the experiences and achievements reached by implementing the strategy of “Integrated Production Management by Processes” which goal is to create and implement a management model that will contribute to the optimization of the Asset performance, integrating through the people, management processes, workflows and information and communication technologies.
The “Integrated Production Management by Processes” model, is based on five elements that work integrated and coordinated way; these are:
• Organizational issues.
• Work methodologies.
• Information management.
• Monitoring key performance indicators (KPI).
• Production costs management
The proposal on this paper is based on developing a business process management methodology for PEMEX, by applying the 5 elements of the model to measure current performance of the production assets in order to find the existing gaps between the current management model and the Integrated Production Management by Processes and implement an action plan to close those gaps. In order to homologate and standardize the measurements in PEMEX’s assets, a Capability Maturity Model was developed according to the ISO 9004-2010 and Mexican Standard NMX-CC-9004-IMNC-2009. The maturity model allows weighting each one of the 5 elements into 5 dimensionless levels. The lowest level 1 means that the asset is in the initial stage and it has the Vision of a Functional Management; on the other hand, the highest level 5 means that asset has implemented the new model and has reached a Sustainable Management. To implement the Integrated Production Management by Processes, assets need to demonstrate that Level 4 has been reached.