bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of a Wind Tunnel for Use in Offshore Wind Turbine Development
Authors: Newton James M. , Cameron Matthew P. , Urbina Raul , Kimball Richard W. , Goupee Andrew J. , Thiagarajan Krish P. 
Published: October 2015

In this work a wind tunnel with an open jet configuration is investigated for use in offshore wind turbine testing. This study characterizes the open-jet wind-tunnel using measurements of the velocity field detailing mean velocities and turbulence intensities with and without a scaled wind turbine. Measurements have been taken downstream to evaluate the expected area of turbine operation and the shear zone. The effects on the flow due to the wake and turbine blockage have also been identified. Additionally, the combination of honeycomb and screens necessary to produce a homogeneous flow at the desired velocity with low turbulence intensity has been identified.
This work provides a useful data set that will be used as a benchmark to evaluate the benefits of recirculating wind tunnels. The data set has resulted in identifying conditions that would prevent producing the desired flows. The data set has also resulted in recommendations concerning the shape of the wind tunnel sections at the University of Maine’s wind-wave (W2) facility to minimize its interactions with the turbine wake expansion, turbine blockage, and the turbine associated wake shear zone.
Partial Safety Factors and Design Fatigue Factors for Design Requirements of Tidal Turbines: A Risk Based Approach
Authors: Simeon Gaizka Zarraonandia , Chen Piing , Ferreira Claudio Bittencourt 
Published: October 2015

This paper describes the methodology behind the partial safety factors and design fatigue factors of the DNV GL standard for certification of tidal turbines. The standard follows a risk based approach that allows the adjustment of the design requirements to the identified risk level of the system.
The work undertaken in this study has involved the identification of the uncertainties during the design process. Tidal turbines are located in highly energetic sites which are very difficult to characterise, hence site conditions are one of the largest sources of uncertainty. Key parameters like turbine inflow conditions or predictions of extreme values are still grey areas. Load simulation tools are still quite uncertain and are often dependent on the experience of the people running them.
Both partial safety factors and design fatigue factors have been calibrated to different target safety levels with due account for the uncertainties introduced by load models as well as site characterisation. The different target safety levels have been selected in accordance to the risk associated to structural failures of tidal turbine support structures and aim for a more streamlined design from the safety requirements point of view.
Deterministic Simulation of Breaking Wave Impact and Flexible Response of a Fixed Offshore Wind Turbine
Authors: Bunnik Tim , Helder Joop , de Ridder Erik-Jan 
Published: October 2015

The effects of operational wave loads and wind loads on offshore mono pile wind turbines are well understood. For most sites, however, the water depth is such that breaking or near-breaking waves will occur causing impulsive excitation of the mono pile and consequently considerable stresses, displacements and accelerations in the mono pile, tower and turbine.
Model tests with a flexible mono pile wind turbine were carried out to investigate the effect of breaking waves. In these model tests the flexibility of the turbine was realistically modelled. These model tests were used for validation of a numerical model for the flexible response of wind turbines due to breaking waves. A focusing wave group has been selected which breaks just aft of the wind turbine.
The numerical model consists of a one-way coupling between a CFD model for breaking wave loads and a simplified structural model based on mode shapes. An iterative wave calibration technique has been developed in the CFD method to ensure a good match between the measured and simulated incoming wave profile. This makes a deterministic comparison between simulations and measurements possible. This iteration is carried out in a 2D CFD domain (long-crested wave restriction) and is therefore relatively cheap. The calibrated CFD wave is then simulated in a (shorter) 3D CFD domain including a (fixed) wind turbine. The resulting wave pressures on the turbine have been used to compute the modal excitation and subsequently the modal response of the wind turbine. The horizontal accelerations resulting from this one-way coupling are in good agreement with the measured accelerations.
Nonlinear Analysis of Axisymmetrically Wrinkled Pipes Under Axial Loads and Internal Pressures
Authors: Dhar Ashutosh Sutra , Muntakim Abu Hena 
Published: October 2015

Nonlinear finite element analysis of axi-symmetrically dented/wrinkled pipe has been presented in this paper. The pipe including surrounding soil was modelled using three different approaches to indicate the effects of modelling approaches on the simulation of pipe behavior. In the first approach, pipe was modelled with the geometry of the dented/wrinkled pipe without consideration of any residual stress and stress history. In the second approach, residual stress was applied at the nodal points of the pipe geometry modelled as in the first approach. In the third approach, a dent/wrinkle was created on the pipe wall through applying nodal displacements to include residual stress as well as the stress history effects.
The analysis revealed that the first approach provides an un-conservative estimation of the pipe capacity. The second approach provides a reasonable estimation of the pipe capacity for elastic perfectly plastic material. However, the second approach provides a conservative estimation for strain hardening material, since pipe stress history is not considered. For strain hardening materials, both residual stress and the stress history should be considered for the simulation of the pipe behavior. The surrounding soil appears not to contribute to the capacity of the pipes under the loading conditions investigated.
Systematic Testing of the Fatigue Performance of Submerged Small-Scale Grouted Joints
Authors: Schaumann Peter , Raba Alexander 
Published: October 2015

With an increasing demand for renewable energy, offshore wind farms become more and more important. Within the next 15 years the German government intends to realize offshore wind farms with a capacity of 15 GW of electrical energy. This corresponds to approximately 3000 to 4000 new turbines.
The grouted joint is a common structural detail for the connection between substructure and foundation piles in offshore wind turbine structures. For lattice substructures such as jackets, the connection is located just above the seabed and is permanently surrounded by water.
Prior investigations by Schaumann et al. showed that the surrounding water may have an impact on the fatigue performance of grouted joint specimens. Thus far, very few results of submerged fatigue tests on grouted joint specimens are published and their statistical reliability is insecure.
Within this paper, 24 individual test results are presented. Regarding test parameters, the focus is set on two different applied load levels, two different loading frequencies and two different grout materials. All parameters are varied in a factorial experiment and are statistically evaluated.
The evaluation shows that load level and loading frequency have a significant effect on the fatigue performance of the connection. Moreover, both effects are significantly correlated. For the used grout materials no significant impact is visible, which can be explained by their similarity regarding mechanical properties and micro structure. Furthermore, the mean displacement and the stiffness degradation of the specimens during fatigue tests are discussed in detail in the paper.
In conclusion, previously published results on the fatigue performance of submerged small scale grouted joint specimens can be confirmed. Load level as well as loading frequency can be stated as most relevant parameters for the fatigue performance.
The Northern Sea Route vs the Suez Canal Route: An Economic Analysis Incorporating Probabilistic Simulation Optimization of Vessel Speed
Authors: Way Brent , Khan Faisal , Veitch Brian 
Published: October 2015

While previous studies have examined the economics of shipping from Europe to Asia via the Northern Sea Route (NSR) versus the Suez Canal Route (SCR), most have not adequately accounted for the variability in input parameters such as the cost of fuel or the amount of ice encountered on a voyage. Furthermore, no prior study has attempted to utilize speed optimization as part of the analysis.
Because the rate fuel consumption for propulsion is intrinsically linked with vessel speed, reducing speed can create the potential for large savings in fuel costs, along with the added benefit of reduced emissions. However, the reduced speed means a longer transit time, meaning increases in other time based costs, such as daily pay for a ship’s crew. The question then becomes what is the optimal speed?
This paper examines the use of speed optimization to determine whether it is potentially more profitable for a container shipping company to ship from Rotterdam to Yokohama through the SCR year round (Option A) or to ship through the NSR during the months it is passable while using the SCR for the remainder of the year (Option B). A probabilistic model is presented to determine average per trip profits for both options A and B. This model is used in conjunction with a simulation optimization technique to determine the optimum speeds to maximize average per trip profitability for each option. The results show that probabilistic simulation optimization of vessel speed may better inform shipping companies as to the financial impacts of the speeds that they choose to use for shipping and thus enable better decision making as it pertains to both route choice and ships’ speeds. The analysis indicates that speed optimized container shipping year round through the Suez Canal appears to be the more profitable of the 2 options.
Analysis of Aerodynamic Performance of Floating Wind Turbines Using CFD and BEMT Methods
Authors: Make Michel , Vaz Guilherme , Fernandes Gerson , Burmester Simon , Gueydon Sebastien 
Published: October 2015

Scaling effects caused by applying Froude-scaling to both wind and waves during model-testing of floating offshore wind turbines (FOWTs) results in poor model-scale aerodynamic performance of geometrically scaled turbines. This led to the “performance-scaled” MARIN Stock Wind Turbine (MSWT) which showed to be successful in obtaining the correct thrust loads at model-scale conditions. Additionally it was found that conventional blade-element-momentum-theory-based (BEMT) modelling tools are not suitable for model-scale conditions.
Recent research in which these problems have been addressed are presented in this paper. First a 3D CFD study was performed in which the behaviour of the flow over the commonly studied NREL 5MW baseline turbine and the MSWT geometries was performed. Both model and full-scale conditions were studied for a fixed non-moving platform and rotor-only turbine. It was found that scaling effects are indeed significant and a highly three-dimensional and additionally separated flow was observed. Based on these findings two methods were proposed to expand the applicability of BEMT-based tools to off-design and modelscale conditions.
First, instead of using commonly used 2D XFOIL data, 2D CFD RANS data was used. The use of purely 2D data from 2D CFD RANS computations did however not result in the desired improvements when compared to XFOIL-based results. The second proposed method is based on the use of 2D airfoil data obtained by post-processing of 3D flow data coming from 3D CFD computations. This new approach was shown to be successful and can therefore be extremely useful for future model-scale FOWT testing campaigns to do preliminary performance predictions. All BEMT-based and CFD results presented in this paper were compared to model-scale experimental data of the NREL 5MW turbine and the MSWT over the full range of TSR.
Comparison of Real-Time Measured and Predicted Wellhead Fatigue Performance in a Deepwater Drilling Operation
Authors: Mackenzie James , Murdoch Neil , Killbourn Stuart 
Published: October 2015

This paper discusses the use of a real-time monitoring system to track wave driven fatigue damage at critical locations in a subsea well during a 290-day drilling operation in the Mediterranean Sea. Real-time monitoring was employed due to up-front finite element (FE) analysis predicting fatigue damage rates of sufficient magnitude that the required safety factor would not be met.
LMRP/BOP motions were recorded using two subsea monitoring units (each containing accelerometers and angular rate sensors). These were installed on the LMRP and above the lower flex joint. The accelerometer signals were used to deduce the static inclination of the well and the angular rate signals the dynamic inclination due to vessel motion and wave loading on the riser. Data was transmitted in real-time to a central processing unit on board the vessel. This converted the motion data into fatigue damage accumulation using non-linear transfer functions derived from the FE model. The damage was displayed in a simplified format for use in decision-making.
The recorded data revealed the motions of the LMRP/BOP and hence the damage rates in the well to be considerably less than predicted by the FE analysis. The damage rates derived from the monitoring system therefore served as a continuously updating demonstration that an acceptable margin of safety against suffering a fatigue failure was being maintained thus permitting drilling to proceed safely.
A subsequent benchmarking study which additionally involved processing of recorded vessel motion data, current data and seastate data was undertaken to identify possible reasons for the differences between the predicted and measured LMRP/BOP motions. This showed that conservative assumptions made on the soil stiffness (due to limited availability of data), differences between the predicted and measured riser natural periods and differences between the predicted and measured vessel motions all contributed to the LMRP/BOP motions and hence the damage rates predicted by the up-front FE analysis being larger than measured in the field. The systematic identification of the factors which contributed to the differences between the predicted and measured response is described in this paper. Areas where further work would be of value to help improve the reliability of up-front, analytically predicted fatigue damage rates are also discussed.
Predictive Residual Ovality for Reel-Laid Pipelines in Deepwater
Authors: Sriskandarajah T. , Rao Venu 
Published: October 2015

Accurate determination of residual ovality is an important parameter for a successful deployment of single pipeline and pipe-in-pipe in deep waters wherein the integrity of empty pipes during installation depends upon the collapse resistance under external hydrostatic pressure. The reel-lay process of installation during which pipeline undergoes multiple strain cycles due to spooling, reeling and straightening has a significant bearing on pipe ovalisation and hence accurate determination residual ovality at the end of straightening process is one of the key inputs.
It is industry practice to use numerical finite element analysis techniques to predict residual ovality of pipelines as full scale testing is expensive and time consuming. In view of the importance of residual ovality on the pipeline integrity particularly for deepwater applications, an integrated approach of testing and finite element simulation have been used to identify the correct numerical model that predicts residual ovality accurately. This paper discusses the full scale tests performed which include material testing and bend tests performed to simulate spooling and straightening process and the pipeline deformations recorded using laser measurements at different cycles of bending process. The paper presents a brief summary of numerical finite element analyses performed to validate the test results and the effect of element types and material models used in the finite element analyses on the predictability of residual ovality.
The material evolution models and their effect on the predictability of remaining ovality are discussed in the paper. Comparisons are made on the predictive residual ovality for reel lay process on single pipe and pipe-in-pipe. The effect of residual ovality on the pipeline integrity for the lateral buckling limit state under combined bending and external pressure are discussed in the paper.
Model-Scale/Full-Scale Correlation of NRC-OCRE’s Model Resistance, Propulsion and Maneuvering Test Results
Authors: Lau Michael 
Published: October 2015

There are a variety of model ices and test techniques adopted by model test facilities. Most often, the clients would ask: “How well can you predict the full scale performance from your model test results?” Model-scale/full-scale correlation becomes an important litmus test to validate a model test technique and its results. This paper summarizes the model-scale/full-scale correlation performed on model test data generated at the National Research Council - Ocean, Coastal, and River Engineering’s (NRC-OCRE) test facility in St. John’s. This correlation includes ship performance predictions, i.e., resistance, propulsion and maneuvering. Selected works from NRC-OCRE on the USCGC icebreaker Healy, the CCGS icebreaker Terry-Fox, the CCGS R-Class icebreakers Pierre Radisson and Sir John Franklin and the CCGS icebreaker Louis S. St. Laurent were reviewed and summarized. The model tests were conducted at NRC-OCRE’s ice tank with the correct density (CD) EGADS model ice. This correlation is based on the concept that a “correlation friction coefficient” (CFC) can be used to predict full-scale ship icebreaking resistance from model test data. The CFCs have been compared for correlation studies using good-quality full-scale information for the five icebreaker models in the NRC-OCRE’s model test database. The review has shown a good agreement between NRCOCRE’s model test predictions and full-scale measurements.
The resistance and power correlation were performed for five sets of full-scale data. Although there is substantial uncertainty on ice thickness and ice strength within the full scale data sets that contributes to data scattering, the data suggest a conservative estimate can be obtained to address reasonably this uncertainty by increasing the model prediction by 15% that envelopes most data points.
Limited correlation for maneuvering in ice was performed for the USCGC icebreaker Healy. Selected test conditions from the sea trials were duplicated for the maneuvering tests and turning diameters were measured from the arcs of partial circles made in the ice tank. Performance predictions were then compared to the full-scale data previously collected. Despite some discrepancy in ice strength and power level between the model tests and sea trial, the model data agree well with the sea trial data except for three outliers. Otherwise, the maneuvering data show a good correlation between the model test and sea trial results.
Quantification of Risks Associated With a Representative Production Well in the Gulf of Mexico
Authors: Zulqarnain Muhammad , Tyagi Mayank 
Published: October 2015

After Macondo incident a great effort is under way to improve the safety of deepwater drilling and production operations and enhance the capabilities of different well barrier to stop the oil spill on its earliest stages. This study is a part of that collective effort to make offshore operations safe and decrease the associated risks. The main objective of this study is to quantify and categorize the risk associated with a representative well in the Gulf of Mexico during its normal production operations. In order to achieve an appropriate balance between safety and economics of deepwater oil and gas operations, Quantitative Risk Assessment (QRA) techniques can be successfully used. Quantified risk is computed from the product of blowout frequency and volume of oil spilled as a consequence. Blowout frequency is calculated from Fault Tree Analysis (FTA) and spilled oil volume is estimated from simulating multiphase fluid flow and heat transfer in wellbores.
A large number wells are completed with some sort of bottom hole sand control elements to prevent production of sand. The failure of these control elements may have severe consequence and in some cases may result in uncontrolled hydrocarbon flow to the environment as well. A representative production well from the Mississippi Canyon in the Gulf of Mexico is selected for the for quantitative risk assessment (QRA) analysis. The well is completed with cased hole gravel pack and with sand control elements in place. The representative reservoir properties for this well are selected from the literature and uncertainties in properties are accounted for by fitting lognormal distribution and carrying out Monte Carlo simulations. P50 value for the reservoir properties from Monte Carlo simulation is used to find worst case discharge rates by using a commercially available multiphase flow simulator with black oil model.
A Fault Tree is constructed to find the blowout probability based on the equipment failure data. From the minimal cut set method the importance and sensitivity of different well barrier is analyzed and most important areas to focus on are identified. The analysis showed that the constructed fault tree is most sensitive to sand screen failures, followed by subsea production tree and delayed response to a situation of immediate concern.