bluuebunny/crossref_metadata_2025_split huggingface dataset:
Prediction of Extreme Wave Slamming Loads on a Fixed Platform
Authors: Filip Grzegorz P. , Xu Wenzhe , Maki Kevin J. 
Published: September 2018

Design of offshore oil platforms requires accurate prediction of the maximum wave loads due to slamming on horizontal decks. The physical processes that influence the load are the propagation of irregular short-crested wind-driven storm seas, wave breaking, and wave-structure interaction. Furthermore, the ocean is a stochastic environment, so the load and its maximum can be considered as random variables. Ideally, the designer would like to know not only the most probable extreme load, but also the extreme load distribution.
In this paper we will use a novel technique to prescribe wave environments that lead to extreme responses so that high-fidelity simulations of the highly-nonlinear process can be investigated in detail. Specifically, the dynamics of the relative motion of the sea surface and the platform will be assumed via the selection of a sea spectrum, and the extreme-value probability distribution function (PDF) will be calculated for a given exposure window. The novel aspect of the work is in the way that a set of deterministic sea environments will be generated that are amenable for simulation with a state-of-the-art computational-fluid dynamics (CFD) software. The resulting wave environments will be simulated to estimate the extreme-value PDF.
A Surrogate Modeling Approach for Fatigue Damage Assessment of Floating Wind Turbines
Authors: Müller Kolja , Cheng Po Wen 
Published: September 2018

Fatigue analysis for floating wind turbines poses a novel challenge to calculation workflows if a probabilistic load environment is to be considered. The increased complexity of the structure itself as well as its interaction with the environment require a coupled and more detailed analysis with respect to resolution of environmental conditions compared to fixed bottom systems.
Different approaches to address the computing challenge for floating turbines are possible to support engineering judgement and have been investigated in the past, with conservative binning on the one end of the accuracy scale and computation intensive Monte Carlo simulations on the other end. This study investigates the feasibility of regression based surrogate models based on radial basis functions. The investigation performed here is aligned with work performed in the H2020 project LIFES50+. Consequently, the considered system is the DTU 10MW Reference Wind Turbine installed on the LIFES50+ OO-Star Wind Floater Semi 10MW. The site under investigation is the LIFES50+ Site B (Gulf of Maine) medium severity representative site.
Results show a similar convergence of lifetime fatigue load prediction as with Monte Carlo simulations indicating that this technique may be an alternative if a response model of the considered system is of interest. This may be interesting if damage loading is to be calculated at a different site and if a classification of met-ocean conditions is available.
Improved Design of Multi-Rotor Tidal Energy Converters
Authors: de la Portilla Marina Pérez , Piñeiro Amable López , Núñez Rivas Luis Ramón , Guerra Enrique Tremps 
Published: September 2018

There is currently an increasing interest in developing devices that can be used to exploit renewable energy in general and marine renewable energy in particular. Several sources of energy can be obtained from oceans, such as the energy produced by waves, tides, oceanic currents or thermal gradients, etc. It is important to stress that one of the most predictable sources of renewable energy is that derived from tidal and marine currents.
Several manufactures are developing devices with which to harness energy from ocean currents, and there is an extended trend towards the development of horizontal axis rotor turbines (HAT-TEC). There is, however, also a considerable amount of debate regarding both the use of fixed or controllable pitch rotors and the use of one or several rotors per device.
The decisions made in this respect have a great effect on the behaviour of the devices and the viability of the park as regards whether or not it will be technically and economically feasible. It is, therefore, necessary to be able to compare models and tools in order to design and choose the best and most feasible option. The tools most commonly used for metric comparison are: LCOE (Levelized Cost Of Energy), TRL (Technology Readiness Level) and TLP (Technology Performance Level).
This paper presents a formal procedure with which to compare various alternatives: On the one hand, previous results obtained by the GITERM-UPM Research Group as regards mono-rotor and multi-rotor fixed-pitch devices will be shown, together with their general characteristics. The possibilities of controlling them, which is achieved with the group’s own design of a ballast control system that is employed to carry out automatic emersion and immersion maneuvers to reduce the high economic cost of maintenance tasks and repairs, will also be explained.
On the other hand, the challenges involved in improving the design of the multi rotor will be listed, including the increase in the power of the rotor, the simplification of the structure, the improvement of the ability to control the device, etc. A new design for a multi-rotor device will also be presented, which takes advantage of the strengths of previous models and manages to substantially improve the amount of annual energy produced. This new device uses controllable pitch rotors, and its size and the amount of power produced by each generator have been improved.
Finally, an economic comparison is carried out by means of a series of cost-benefit indicators, and a formal procedure with which to compare their benefits through the use of LCOE is also proposed.
Propagation of Steep and Breaking Short-Crested Waves: A Comparison of CFD Codes
Authors: Lande Øystein , Johannessen Thomas Berge 
Published: September 2018

Using the computational fluid domain for propagation of ocean waves have become an important tool for the calculation of highly nonlinear wave loading on offshore structures such as run-up, wave slamming and non-linear breaking wave kinematics.
At present, there are many computational fluid dynamics (CFD) codes available which can be employed to calculate water wave propagation and wave induced loading on structures. For practical reasons, however, the use of these codes is often limited to the propagation of regular uni-directional waves initiated very close to the structure, or to investigating the properties and loading due to measured waves by fitting a numerical wave to a measured wave profile.
The present paper focuses on the propagation of steep irregular and short crested wave groups up to the point of breaking. Indeed, this is challenging because of the highly nonlinear behavior of irregular wave groups as steepness increases and they approach the point of breaking. The complexity further increases with the introduction of short-crestedness requiring computation in a large 3-dimentional domain.
Two CFD codes are used in this comparison study which are believed to be well conditioned for wave propagation, the commercial code ComFLOW (available through the ComFLOW JIP project) and the open-source code BASILISK. The primary objective of this paper to show the two CFD codes capability of recreating measured irregular wave groups, using the known linear wave components from the model test as input to fluid domain. Wave elevation is measured at several locations in the close vicinity of the focus point. The comparison is carried out for a selection of events with variation in steepness, wave spreading and wave spectrum.
Optimization of the Structural Performance for Corrugated Blast Panels on Offshore Platforms
Authors: Voorde John Vande , Van den Abeele Filip , Cooreman Steven 
Published: September 2018

Blast panels are integral structures in offshore topside modules to protect personnel and safety critical equipment by preventing the escalation of events due to hydrocarbon explosions. As such, blast panels are expected to retain their integrity against any blast loading and subsequent hydrocarbon fire. Most of the blast panels currently installed in offshore structures have been designed using simplified calculation approaches such as the Single Degree of Freedom (SDOF) models, as recommended by offshore design codes and industry recommended practices.
In this paper, the Non-Linear Finite Element Analysis (NLFEA) technique is used to simulate the structural response of corrugated panels subjected to blast loading. Detailed numerical analyses allow identifying the limits of the SDOF approach, and exploring different design options to optimize the structural response of corrugated blast panels.
The blast load profile corresponding to an explosion is one of the most important factors to consider in the structural analysis. The mechanism of hydrocarbon explosions is very complex, and the corresponding blast load profile intimately depends on the type of explosion, the congestion and the structural confinement. A sensitivity analysis is performed to investigate the influence of the blast pulse shape, and in particular to evaluate the effect of the maximum peak pressure and the exposure time.
To explore the benefits of introducing higher strength steels in demanding offshore applications, pressure-impulse diagrams have been derived for different high strength steel grades. In our analysis, (ultra)high strength cut-to-length plates from hot rolled coil are proposed to optimize the design of the blast panel whilst preserving the structural performance under demanding load conditions.
Real-Time Wellhead Bending Moment Measurement Using Motion Reference Unit (MRU) Sensors and Machine Learning
Authors: Srikonda Rohit , Haakonsen Rune , Russo Massimiliano , Periyasamy Peri 
Published: September 2018

In order to facilitate real-time monitoring of accumulated wellhead fatigue damage, it is necessary to measure the wellhead bending moment in real-time. This paper presents a novel method to estimate the wellhead bending moment in realtime using acceleration and inclination data from the motion reference unit (MRU) sensors installed on BOP and LRJ, riser tension data and a trained neural network model. The method proposed in this paper is designed with a Recursive Neural Network (RNN) model to be trained to estimate the wellhead bending moment in real-time with high accuracy based on motion MRU sensor data and riser tension time series of a few previous cycles. In addition to the power of modeling complex nonlinearities, RNNs provide the advantage of better capturing the dynamic effects by learning to recognize the patterns in the sensor data and riser tension time series.
The RNN model is trained using virtual sensor data and wellhead bending moment from a finite element (FE) model of the drilling riser subjected to irregular wave time domain analyses based on a training matrix with limited number of significant height (Hs) and peak period (Tp) combinations. Once trained, tested and deployed, the RNN model can make real-time estimation of the wellhead bending moment based on MRU sensor data and riser tension time series. The RNN model can be an efficient and accurate alternative to a physical model based on the indirect method for real-time calculation of wellhead bending moment using real-time sensor data. A case study is presented to explain the training procedures for the RNN model. A set of test cases that are not included in the training dataset are used to demonstrate the accuracy of the RNN model using Root Mean Squared Error (RMSE), Normalized Root Mean Squared Error (NRMSE) and coefficient of determination (R2) as a metrics.
Fully-Coupled Aero-Hydrodynamic Simulation of Floating Offshore Wind Turbines by Different Simulation Methods
Authors: Cheng Ping , Wan Decheng 
Published: September 2018

To accurately predict the critical loads due to wind and wave is one of the common challenges in designing a floating offshore wind turbine (FOWT). The fully-coupled aero-hydrodynamic simulation of a floating offshore wind turbine, the NREL-5MW baseline wind turbine mounted on a semi-submersible floating platform, is conducted with two methods. Firstly, the in-house code naoe-FOAM-os-SJTU, which is developed on the open source platform OpenFOAM and coupled with the overset grid technique, is employed for the directly CFD computations. And another in-house code FOWT-UALM-SJTU developed by coupling the unsteady actuator line model (UALM) with naoe-FOAM-SJTU is also utilized for coupling simulations. In both models, the three-dimensional Reynolds Averaged Navier-Stokes (RANS) equations are solved with the turbulence model k-ω SST, and the Pressure-Implicit with Splitting of Operations (PISO) algorithm is applied to solve the pressure-velocity coupling equations.
Both two solvers provide reasonable results of main aerodynamic loads as well as the main hydrodynamic forces. The FOWT-UALM-SJTU solver achieves better computational efficiency by simplifying the blade structure as actuator line models, while the naoe-FOAM-os-SJTU solver provides more accurate detailed flow information near the turbine blades.
Fully Coupled Analysis of Ship Motion and Sloshing Tanks in Regular and Irregular Waves
Authors: Zhuang Yuan , Wan Decheng 
Published: September 2018

Fully coupled analysis of ship motion and sloshing tank in waves is essential for floating structures which store and transports natural gas. For partially filled tanks would generate violent sloshing due to external wave excitation, and the sloshing flow can consequently affect ship motion. Therefore, how to evaluate ship motion and sloshing phenomenon in tank is of great importance, especially under real sea state, when wave induced sloshing would be more complex than that under linear wave condition.
In the present work, a CFD-based method is applied to simulate both external wave field and inner sloshing tank field in regular waves and irregular waves. The ship is a simplified FPSO, with two LNG tanks.
All the numerical simulations are carried out by the in-house CFD code naoe-FOAM-SJTU, which is developed on the open source platform OpenFOAM. The regular and irregular wave condition is simulated based on open source toolbox waves2Foam. The main parameters of coupling effect of ship motion and sloshing tank, such as the time history of ship motion, sloshing phenomenon in tanks are obtained by our computations. The predicted results for the coupling effects of ship motion and sloshing tank in regular waves are compared with the corresponding experimental data. The comparison is satisfactory and shows that the CFD method has the ability to simulate coupling effects of ship motion and sloshing tank in waves.
On the Uncertainties of Estimating JONSWAP Spectrum Peak Parameters
Authors: Ewans Kevin , McConochie Jason 
Published: September 2018

A spectral description of the wave spectrum is usually required in the design of offshore structures, and a generalised form of the JONSWAP spectrum is often used. The JONSWAP spectrum involves parameters that allow flexibility in the specification of the spectral peak, which is important for the response of both fixed and floating structures, but particularly for the floating structures. The peak of the wave spectrum is also important in nonlinear effects that for example contribute to the probability of a large crest occurring in a sea state time series realisation in a model basin, used to test a design platform.
There has been a number of studies focused on the uncertainties of JONSWAP parameter estimates. We review these to establish an overview of the present understanding of the uncertainties, and we undertake further analyses to investigate the sensitivity of the uncertainties to the method of analysis and the types of data typically available for analysis, including both time series and spectral data.
Green Water Assessment for Marine and Offshore Applications: Structural Response of the ULCS Breakwater
Authors: Malenica Šime , Lee Byung Hyuk , Vladimir Nikola , Gatin Inno , Monroy Charles , De Lauzon Jerome 
Published: September 2018

Green water loading which occurs during the floating body operations in heavy weathers can be very dangerous for the structural integrity of the superstructures and the equipment’s located at the upper decks. The correct modeling of the green water loading and the corresponding structural response is far from trivial and many different physical aspects need to be taken into account at the same time. Depending on the type of the floating body, the overall procedure involves the use of the different numerical tools at different steps. For off-shore type structures the procedure is slightly more complicated than for ships because, in addition to the classical seakeeping simulations, the mooring software also needs to be used. In all cases the final design conditions should be modeled using the complex hydro-structure interaction tools.
In the present work the overall methodology is demonstrated and applied to the case of the evaluation of the structural response of the breakwater on the Ultra Large Container Ship (ULCS).
TurkStream Collapse Test Program
Authors: Timms Chris , Swanek Doug , DeGeer Duane , Meijer Arjen , Liu Ping , Jurdik Erich , Chaudhuri Jay 
Published: September 2018

The TurkStream pipeline project is designed to transport approximately 32 billion cubic meters of natural gas annually from Russia to Turkey under the Black Sea, with more than 85% of the deep-water route being deeper than 2000 m. The offshore section is intended to consist of two parallel lines, each approximately 900 km long. The preliminary stages of the front end engineering design (pre-FEED) phase was managed by INTECSEA. To support the analyses and design of the deepest portions, a full scale collapse test program was performed by C-FER Technologies (C-FER). This collapse test program, which included 62 full-scale collapse and pressure+bend tests, 54 medium-scale ring collapse tests, and hundreds of small-scale tests, was primarily aimed at measuring, quantifying and documenting the increase in pipe strength and collapse resistance resulting from the thermal induction heat treatment effect (thermal ageing) that arises during the pipe coating process. Two grades of 32-inch (813 mm) outside diameter (OD) line-pipe, SAWL450 and SAWL485 with wall thicknesses of 39.0 mm or 37.4 mm, respectively, were supplied from various mills for testing. The collapse test program objectives were as follows:
• Determine the collapse resistance of line pipes originating from various pipe mills;
• Determine the pressure+bend performance of line pipes originating from various pipe mills;
• Measure the effect of thermal ageing on material and collapse testing results, including the impact of multiple thermal cycles; and
• Evaluate the results of medium-scale ring collapse tests as compared to full-scale tests.
This paper presents selected results of this work, along with some comparisons to predictive equations.
The Application of Fuzzy-Ball Drilling Fluid to Deepwater Drilling to Deal With Highly Mineralized Formation Brines and Low-Temperature Environment
Authors: Wei Panfeng , Zheng Lihui , Yang Mingzheng , Chen Yuanhang 
Published: September 2018

For deepwater oil and gas well drilling with the issue of highly mineralized formation brines, it is required that the drilling fluid properties are not affected by the high salinity formation fluid and the low-temperature environment. A novel drilling fluid mainly consists of fuzzy-ball fluid, which has an excellent tolerance to salinity and low temperature, has the potential to be applied for deepwater drilling to achieve safe and efficient drilling tasks.
Experimental studies and field tests have been carried out to characterize the rheological properties of fuzzy-ball drilling fluid under different conditions of brine salinity and test temperature. In the experimental test, fuzzy-ball fluids with different densities are prepared with brines of varying salinity mineralized by Ca2+ and Mg2+. The rheological curves are plotted from different apparent viscosities and shear stresses under different shear rates measured by a rheometer under 10 ∼ 80°C and a six-speed viscometer at 0°C.
The results positively showed that the yield stress of fuzzy-ball fluid is stable at a relatively high value with the variation of fluid salinity and temperature. The apparent viscosity slightly increases with the decrease of salinity and temperature. It can be claimed that the rheological properties of fuzzy-ball drilling fluid are stable within the range of salinity and temperature investigated experimentally.
Field tests have been conducted during several workover jobs, the rheological properties of fuzzy-ball drilling fluid were stable at temperatures and salinities on site. Thus, it can be proved that the novel fuzzy-ball drilling fluid could be applied in deepwater drilling under the high salinity formation fluid and low-temperature environment.
Learnings From Strain Measurements on an In-Field Conductor and Wellhead System
Authors: Shankaran Rohit , Rimmer Alexander , Haig Alan 
Published: September 2018

In recent years due to use of drilling risers with larger and heavier BOP/LMRP stacks, fatigue loading on subsea wellheads has increased, which poses potential restrictions on the duration of drilling operations. In order to track wellhead and conductor fatigue capacity consumption to support safe drilling operations a range of methods have been applied:
• Analytical riser model and measured environmental data;
• BOP motion measurement and transfer functions;
• Strain gauge data.
Strain gauge monitoring is considered the most accurate method for measuring fatigue capacity consumption. To compare the three approaches and establish recommendations for an optimal approach and method to establish fatigue accumulation of the wellhead, a monitoring data set is obtained on a well offshore West of Shetland. This paper presents an analysis of measured strain, motions and analytical predictions with the objective of better understanding the accuracy, limitations, or conservatism in each of the three methods defined above.
Of the various parameters that affect the accuracy of the fatigue damage estimates, the paper identifies that the selection of analytical conductor-soil model is critical to narrowing the gap between fatigue life predictions from the different approaches. The work presented here presents the influence of alternative approaches to model conductor-soil interaction than the traditionally used API soil model.
Overall, the paper presents the monitoring equipment and analytical methodology to advance the accuracy of wellhead fatigue damage measurements.