bluuebunny/crossref_metadata_2025_split huggingface dataset:
Validation of Hot Corrosion and Fatigue Models in HOTPITS
Authors: Chan K. S. , Burns J. T. , Enright M. P. , Moody J. , Goodrum W. 
Published: December 2019

Abstract
HOTPITS is a set of physics-based modeling tools for treating Type II hot corrosion in Ni-based superalloys. The methodology includes modeling the nucleation, growth, and coalescence of pits and microcracks as a random process, as well as the transition of pits to micrcracks and the propagation of the resulting large crack to failure. In this investigation, critical experiments were performed on coupon and low-cycle fatigue (LCF) specimens in order to validate the hot corrosion and the fatigue models in HOTPITS. The pit nucleation, growth, and coalescence models in HOTPITS including the assumption of a random process are validated by the hot corrosion critical experiments performed at two salt contents. The LCF critical experiments, performed using a marker band protocol, validated the stress concentration factor-based models used to predict the pit-to-crack transition in the HOTPITS tool.
Development and Validation of a General and Robust Methodology for the Detection and Classification of Gas Turbine Sensor Faults
Authors: Manservigi Lucrezia , Venturini Mauro , Ceschini Giuseppe Fabio , Bechini Giovanni , Losi Enzo 
Published: December 2019

AbstractSensor fault detection and classification is a key challenge for machine monitoring and diagnostics, since raw data cleaning represents a key process in the gas turbine industry. To this end, this paper presents a comprehensive approach for detection, classification, and integrated diagnostics of gas turbine sensors (named DCIDS), which was previously developed by the authors and has been substantially improved and validated by means of field data. For a single sensor or redundant/correlated sensors, the improved diagnostic tool, called improved-DCIDS (I-DCIDS), can identify seven classes of faults, i.e., out of range, stuck signal, dithering, standard deviation, trend coherence, spike, and bias. First, this paper details the I-DCIDS methodology for sensor fault detection and classification. The methodology uses basic mathematical laws that require some user-defined configuration parameters, i.e., acceptability thresholds and windows of observation. Second, a sensitivity analysis is carried out on I-DCIDS parameters to derive some rules of thumb about their optimal setting. The sensitivity analysis is performed on four heterogeneous and challenging datasets with redundant sensors acquired from Siemens gas turbines (GTs). The results demonstrate the diagnostic capability of the I-DCIDS approach in a real-world scenario. Moreover, the methodology proves to be suitable for all types of datasets and physical quantities and, thanks to its optimal tuning, can also identify the exact time point of fault onset.
Investigation of Wind Flow Conditions on the Flight Endurance of UAVs in Hovering Flight: A Preliminary Study
Authors: Scicluna Leo , Sant Tonio , Farrugia Robert N. 
Published: December 2019

Abstract
Over the past decade the use of Unmanned Aerial Vehicles (UAVs) for the inspection of turbine blades has been registering steady progress and is fast becoming a well-established inspection methodology especially at offshore wind farms. A UAV operating in the open field is subject to varying ambient conditions which have an effect on the power required to maintain stable flight. This may have an impact on the flight endurance of the UAV, especially when operating in windy conditions. Simulations are a very useful tool for estimating the impact of such ambient conditions on the performance and flight endurance of a UAV. However, it is extremely difficult to accurately model all the dynamics at play in the open field where flow conditions are highly stochastic. Few open field studies necessary to validate such simulation models have been carried out to date in this regard. In this study, the impact of open field wind conditions on the flight endurance of a hovering UAV is investigated. The test vehicle used in this study is a quadrotor UAV, which was fitted with an array of sensors to monitor power consumption parameters of the propulsion motors whilst the vehicle is hovering at a fixed altitude above the ground. The quadrotor was also fitted with an ultrasonic wind sensor in order to measure the relevant wind parameters that the quadrotor was being subjected to during the hovering study. The test UAV was flown in different ambient conditions to establish the impact on the UAV flight endurance when subjected to different wind speeds. Results from a series of UAV test flights in the open field indicated that the power required by the UAV to maintain hovering flight decreases as the wind speed increases.
Modelling the Aerodynamics of a Floating Wind Turbine Model Using a CFD-Based Actuator Disc Method
Authors: Bezzina Ryan , Sant Tonio , Micallef Daniel 
Published: December 2019

Abstract
Significant research in the field of Floating Offshore Wind Turbine (FOWT) rotor aerodynamics has been documented in literature, including validated aerodynamic models based on Blade Element Momentum (BEM) and vortex methods, amongst others. However, the effects of platform induced motions on the turbine wake development downstream of the rotor plane or any research related to such areas is rather limited. The aims of this paper are two-fold. Initially, results from a CFD-based Actuator Disc (AD) code for a fixed (non-surging) rotor are compared with those obtained from a Blade Element Momentum (BEM) theory, as well as previously conducted experimental work. Furthermore, the paper also emphasises the effect of tip speed ratio (TSR) on the rotor efficiency. This is followed by the analysis of floating wind turbines specifically in relation to surge displacement, through an AD technique implemented in CFD software, ANSYS Fluent®. The approach couples the Blade Element Theory (BET) for estimating rotating blade loads with a Navier Stokes solver to simulate the turbine wake.
With regards to the floating wind turbine cases, the code was slightly altered such that BET was done in a transient manner i.e. following sinusoidal behaviour of waves. The AD simulations were performed for several conditions of TSRs and surge frequencies, at a constant amplitude. Similar to the fixed rotor analysis, significant parameters including thrust and power coefficients, amongst others, were studied against time and surge position. The floating platform data extracted from the AD approach was compared to the non-surging turbine data obtained, to display platform motion effects clearly. Data from hot wire near wake measurements and other simulation methods were also consulted.
Integrating Compressed Air Energy Storage (CAES) in Floating Offshore Wind Turbines
Authors: Vella Peter P. , Sant Tonio , Farrugia Robert N. 
Published: December 2019

Abstract
The design of an offshore energy storage system carries unknowns which need to be studied at an early stage of the project to avoid unnecessary costs of failures. These risks have led to an increasing dependence on more sophisticated mathematical models.
This paper refers specifically to energy storage in the offshore wind farming industry and has the objective of proposing an adiabatic compressed air energy (A-CAES) system which would be integrated on a semi-submersible offshore wind turbine (OWT) platform. Calculations in respect to the sizing of the main sub-components of the system are included and estimates for the overall round trip efficiency are presented.
Preliminary calculations to size the various parts of the energy storage system (ESS) have been carried out based on the energy availability of an offshore 8 MW wind turbine with real wind data from the North Sea. The load data to determine the lowest 12-hour demand period was taken from the Nordpool database. The calculations of the proposed conceptual design are based on an operational scenario in which the 24-hour period of a particular day is split in a 12-hour charging and 12-hour discharging cycle. For charging, a 5-bank, 2-stage compressor train is used to pressurize a number of steel cylindrical vessels with compressed air. This is followed by a process in which the compressed air is discharged across 12 hours using a 2-bank, 2-stage expander turbine. The multiple compression banks enable a modular power delivery to the air storage vessels, with the number of compressors utilized varying subject to wind availability. The two stages allowed for the air to be cooled in between the stages using heat exchangers, transferring the heat of compression to a pressurized sea water circuit. The hot water would be stored in thermally insulated vessels at 350°C to heat the inlet expanding air in the discharge period. A 70 and 100 Bar charging scenarios, both with a cushion pressure (CP) in the air storage vessel (ASV) of 10 Bar at the end of the discharge cycle have been considered.
Standard performance criteria are calculated such as compression and expansion ratios, inlet and outlet temperatures for the respective expansion and compression air streams and flow rates within the heat exchangers to come up with an indicative sizing proposal for the respective turbo machinery and storage vessels making up the system. Round trip efficiencies are also calculated.
The study determined that a CAES system consisting of 9 compressed air storage vessels operating with a peak pressure of 100 Bar should meet the storage requirements. It is also estimated that the entire CAES system would require around 1082 m2 of deck area on the platform to accommodate the pressure vessels, the compressor and expander trains, the heat exchanger and the hot water storage vessel.
Numerical Analysis of VIV on Drillstring During CPT in Shallow High-Current Sea
Authors: Yamamoto Marcio , Masanobu Sotaro , Yamamoto Joji , Ban Katsuo , Ikenobu Masayuki , Izumida Tamotsu , Sakamoto Takashi 
Published: December 2019

Abstract
To design the foundation of a fixed-type wind turbine, the geotechnical data of the region in different depths below the seafloor must be surveyed using a cone penetration test (CPT). A common methodology to carry out the CPT in shallow water is to use a drillstring to drill a well. Then the drillstring must be anchored and a cone probe is conveyed within the drillstring to survey the undisturbed soil a few meters below the bit. However, during the period the drillstring is anchored in a relative high-current environment, it will be exposed to the vortex-induced vibration (VIV). In this article, we will present the VIV numerical analysis to assess the stress and accumulate fatigue on the drillstring. The simulation was calculated in the frequency domain using commercial software for marine riser analysis used by the Petroleum Industry. We compared two different drillstrings, one composed by Bottom Hole Assembly (BHA) and drill pipe and the other using BHA and heavyweight drill pipe. The VIV results show slightly better performance of the string composed by heavy weight drill pipes.
Performance Evaluation of Dynamic HV Cables With Al Conductors for Floating Offshore Wind Turbines
Authors: Thies Philipp R. , Harrold Magnus , Johanning Lars , Grivas Konstantinos , Georgallis Georgios 
Published: December 2019

Abstract
Floating Offshore Wind turbine installations will require HV dynamic power cables to be connected to the of longer length static export power cables. Experience from offshore wind installations has highlighted the criticality of power cables, underlining the need for high integrity, yet cost effective cable solutions. This paper will assess the mechanical performance and load parameters for an Aluminum power conductor cable. Whilst copper is the conventional choice due to its lower resistive losses, Aluminum cores are increasingly used for static power cables, due to their benefits regarding overall cable weight and material cost. The work presented adopts a coupled aero-elastic and hydrodynamic modelling approach to simulate the behavior of the well-documented OC4 semi-sub platform, together with the 5MW NREL wind turbine. The model allows a direct comparison between the two cable types, maintaining the overall system and environmental conditions.
The results inform the design envelope regarding the ultimate load conditions a for the two principle cable designs, providing global load estimates, such as effective tension and bending stresses, to inform the local stress analysis. Furthermore, the results will form the basis for future physical demonstration and validation tests.
This paper will be of interest to technology developers and practitioners concerned with submarine dynamic power cables, offer a methodology to directly compare and evaluate different cable design options, and providing some design guidance for and aluminum conductor cables.
Demonstration of the Intelligent Mooring System for Floating Offshore Wind Turbines
Authors: Harrold Magnus J. , Thies Philipp R. , Halswell Peter , Johanning Lars , Newsam David , Bittencourt Ferreira Claudio 
Published: December 2019

Abstract
Existing mooring systems for floating offshore wind turbines are largely based on designs from the oil and gas industry. Even though these can ensure the safe station keeping of the floating wind platform, the design of the mooring system is currently largely conservative, leading to additional expense in an industry striving to achieve cost reduction. Recent interest in the usage of mooring materials with non-linear stiffness has shown that they have the potential to reduce peak line loads, ultimately reducing cost. This paper reports on the combined physical testing and numerical modeling of a hydraulic-based mooring component with these characteristics. The results suggest that the inclusion of the component as part of the OC4 semi-submersible platform can reduce the peak line loads by 10%. The paper also discusses a number of challenges associated with modeling and testing dynamic mooring materials.
Loading and Structural Analysis of the Self-Aligning HyStOH Floating Wind Turbine Concept
Authors: Manjock Andreas , Starr Markus S. 
Published: December 2019

Abstract
This paper summarizes the results of the implementation and verification of a hydro-aero-servo-elastic load simulation model for a self-aligning floating offshore wind turbine (FOWT) combined with a structural analysis methodology of this FOWT structure. The main focus is a comparison of a rigid and a flexible support structure representation in the load simulation. This investigation is part of the multiparty project for the ‘Hydrodynamic and Structural Optimization of a Semi-submersible Offshore Wind Turbine’ (HyStOH), joining partners from science and industry and financially supported by the German Ministry of Economics Affairs and Energy, BMWi (Bundesministerium für Wirtschaft und Energie).
WindCrete Fatigue Verification
Authors: Trubat Pau , Bairan Jesús , Yagüe Adrián , Molins Climent 
Published: December 2019

Abstract
WindCrete is an offshore concrete spar type platform for Wind Turbines developed at Universitat Politècnica de Catalunya – BarcelonaTech. The main characteristics of the platform are its monolithic configuration and the use of concrete as main material. The monolithic nature allows avoiding joints between the substructure and the tower increasing the service life of the structure. The use of concrete increases the resistance when exposed to an offshore environment but requires ensuring a full compression state along the structure to avoid cracking. Thus, the platform is post-tensioned by longitudinal tendons along its length.
Adequate fatigue design is a key factor to ensure the reliability of offshore structures. Floating Offshore Wind Turbines are subjected to cyclic phenomena coming from waves, wind, rotor-induced vibrations and structural vibrations. These loads have to be considered in order to assess the fatigue life of offshore structures. Furthermore, pre-stressed concrete adds an internal load such that it avoids the presence of tension stresses at any given section, which has a positive influence on the fatigue response of the structure by increasing its fatigue resistance. An excess of compression can, however, also induce an adverse effect on the fatigue resistance of the concrete.
In order to study the fatigue behaviour of WindCrete when fitted with a 5MW Wind Turbine, a Fatigue Limit State verification is performed according to the DNVGL-ST-0437 for load cases definition and FIB Model Code (2010) for fatigue structural verification. The location chosen to install WindCrete is the Gulf de Lion, at the west of the Mediteranian Sea off the coast of Catalunya with a mean wind speed above 9 m/s. The metocean conditions for design purpose are presented, which are obtained from available environmental data.
A total of 458 simulation cases are performed using the NREL FAST software assuming wind and wave co-directionally, and quasi-static mooring response for Parked and Power-Production operational modes. Assuming an elastic response of the tower, the internal stresses at the tower base are obtained for all the simulations. Then, a fatigue analysis is performed at the tower base through a cumulative damage approach based on the Palmgren-Miner rule. The analysis accounted for the multiaxial stresses produced by the combination of axial, bending and tangential forces. The S-N material curves were defined according to the Model Code 2010 method, which accounts for the effect of the stress range as well as the average stress.
Bichromatic Wave Selection for Validation of the Difference-Frequency Transfer Function for the OC6 Validation Campaign
Authors: Tom Nathan , Robertson Amy , Jonkman Jason , Wendt Fabian , Böhm Manuela 
Published: December 2019

Abstract
The focus of the Offshore Code Comparison Collaboration, Continuation, with Correlation and unCertainity (OC6) project, which operates under the International Energy Agency Wind Task 30, is to refine the accuracy of engineering tools used to design offshore wind turbines. In support of this work, a new validation campaign is being developed that seeks to better understand the nonlinear wave loading that excites floating wind systems at their low-frequency, rigid-body modes in surge and pitch. The validation data will be employed in a three-way validation between simplified engineering tools and higher-fidelity tools, such as computational fluid dynamics (CFD). Irregular wave spectrums, which are traditionally used to examine the nonlinear wave interaction with offshore structures, are too computationally expensive to be simulated in CFD tools, and so we will employ bichromatic wave cases instead. This paper reviews the process used to choose the bichromatic wave pairs to be applied in the campaign to validate the second-order difference-frequency quadratic and potential loads at the surge and pitch natural frequencies of a floating semisubmersible.
Hybrid Model Tests for Floating Offshore Wind Turbines
Authors: Thys Maxime , Fontanella Alessandro , Taruffi Federico , Belloli Marco , Berthelsen Petter Andreas 
Published: December 2019

Abstract
Model testing of offshore structures has been standard practice over the years and is often recommended in guidelines and required in certification rules. The standard objectives for model testing are final concept verification, where it is recommended to model the system as closely as possible, and numerical code calibration.
Model testing of floating offshore wind turbines is complex due to the response depending on the aero-hydro-servo-elastic system, but also due to difficulties to perform model tests in a hydrodynamic facility with correctly scaled hydrodynamic, aerodynamic and inertial loads. The main limitations are due to the Froude-Reynolds scaling incompatibility, and the wind generation. An approach to solve these issues is by use of hybrid testing where the system is divided in a numerical and a physical substructure, interacting in real-time with each other. Depending on the objectives of the model tests, parts of a physical model of a FOWT can then be placed in a wind tunnel or an ocean basin, where the rest of the system is simulated.
In the EU H2020 LIFES50+ project, hybrid model tests were performed in the wind tunnel at Politecnico di Milano, as well as in the ocean basin at SINTEF Ocean. The model tests in the wind tunnel were performed with a physical wind turbine positioned on top of a 6DOF position-controlled actuator, while the hydrodynamic loads and the motions of the support structure were simulated in real-time. For the tests in the ocean basin, a physical floater with tower subject to waves and current was used, while the simulated rotor loads were applied on the model by use of a force actuation system. The tests in both facilities are compared and recommendations on how to combine testing methodologies in an optimal way are discussed.
Assessing the Impact of Integrating Energy Storage on the Dynamic Response of a Spar-Type Floating Wind Turbine
Authors: Cutajar Charise , Sant Tonio , Farrugia Robert N. , Buhagiar Daniel 
Published: December 2019

Abstract
Offshore wind technology is at the forefront of exploiting renewable energy at sea. The latest innovations in the field comprise floating wind turbines deployed in deep waters that are capable of intercepting the stronger, less turbulent winds farther away from the landmass. Despite being able to augment the power harnessed, wind resources remain intermittent in nature, and so unable to satisfy the energy demand at all times. Energy storage systems (ESS) are therefore being considered a key component to smoothen out the supply-demand mismatch when wind penetration into electricity grids increases. Yet, multiple issues pertaining to the integration of ESSs on large-scale projects arise, including economic, environmental and safety considerations.
This paper presents a novel concept for integrating a hydro-pneumatic energy storage (HPES) system within a spar-type floating offshore wind turbine (FOWT) platform. It aims to assess the technical feasibility of integrating the storage unit within the floater. A preliminary investigation on the influence of integrated storage on the static stability and hydrostatic response of a conventional ballast-stabilised FOWT is conducted, followed by numerical simulations for the dynamic response using ANSYS® AQWA™. Based on the results presented, several conclusions are drawn on the implications of integrating energy storage with floating wind turbine structures. Finally, a preliminary assessment of the thermal efficiency of the storage system based on this specific embodiment is also presented and discussed.
A Systematic Study on Fatigue Loads of Offshore Wind Turbines on Monopiles Foundation
Authors: Peng Lihua , Wang Chao , Niu Shengkai 
Published: December 2019

Abstract
Fatigue failure is one of the most common damage types of monopiles, which are widely used in offshore wind turbines (OWT). In this paper, a systematic study is performed to investigate the influence of stiffness matrix, sea states and wave directions on fatigue loads of monopiles. The stiffness matrix of the monopile determines natural frequency of the whole system and has great effect on fatigue loads. The influence of the pile diameter and length on the stiffness matrix are analyzed, which are calculated based on p-y curve of foundation. Then, three methods for selected sea states are compared. The dynamic response of the monopile using the different selection method under same wind condition are calculated and their contribution to the fatigue load is discussed. Finally, bending moment on the top of monopiles in vary wave direction are analyzed which shows significant on the fatigue. Several suggestions for design of monopile are given to avoid fatigue failure based on this study.