bluuebunny/crossref_metadata_2025_split huggingface dataset:
Three-dimensional stochastic dynamical modeling for wind farm flow estimation
Authors: Lingad M V , Rodrigues M , Leonardi S , Zare A 
Published: June 2024

Abstract
Modifying turbine blade pitch, generator torque, and nacelle direction (yaw) are conventional approaches for enhancing energy output and alleviating structural loads. However, the efficacy of such methods is challenged by the lag in adjusting such settings after atmospheric variations are detected. Without reliable short-term wind forecasting tools, current practice, which mostly relies on data collected at or just behind turbines, can result in sub-optimal performance. Data-assimilation strategies can achieve real-time wind forecasting capabilities by correcting model-based predictions of the incoming wind using various field measurements. In this paper, we revisit the development of a class of prior models for real-time estimation via Kalman filtering algorithms that track atmospheric variations using ground-level pressure sensors. This class of models is given by the stochastically forced linearized Navier-Stokes equations around the three-dimensional waked velocity profile defined by a curled wake model. The stochastic input to these models is devised using convex optimization to achieve statistical consistency with high-fidelity large-eddy simulations. We demonstrate the ability of such models in reproducing the second-order statistical signatures of the turbulent velocity field. In support of assimilating ground-level pressure measurements with the predictions of said models, we also highlight the significance of the wall-normal dimension in enhancing two-point correlations of the pressure field between the ground and the computational domain.
Data-Driven Infrastructure Planning for Offshore Wind Farms
Authors: Saxena Isha , Kazemtabrizi Behzad , Troffaes Matthias C.M. , Crabtree Christopher J. 
Published: June 2024

Abstract
Offshore wind farms are one of the major renewable energy resources that can help the UK to reach its net zero target. Under the 10 point plan of the green revolution, the UK is set to quadruple its wind energy production by increasing its offshore wind capacity to 40GW by 2030 [1]. Research needs to be conducted to study the failure and repair processes of wind turbines under various conditions as the current models make a simplifying assumption that the failure/repair rate remains constant over time. This research aims to create a more accurate model using SCADA data. In this research, different mathematical models are fitted to the time to failure and time to repair data of wind turbine components using frequentist methods (such as Maximum Likelihood Estimation) and Bayesian methods. Further analysis will be conducted using complex system analysis considering the failures of each electrical and mechanical component of the wind turbine. The aim of this project is to perform a more accurate reliability analysis that can help to further drive down costs of wind energy by potentially reducing the downtimes of the wind turbines.
An open-source analysis workflow for geometrically imperfect bolted ring-flanges in wind turbine support structures
Authors: Jorgensen J , Hodkiewicz M , Cripps E , Hassan G M 
Published: June 2024

Abstract
Bolted ring-flanges connect structures via two circular flanges, secured with pre-loaded bolts. In offshore wind turbine support structures the flanges connect the monopile and transition piece, the transition piece and tower, and adjacent tower sections. Fatigue analysis of the bolted ring-flanges in offshore wind turbine support structures is a critical step during design. The consideration of geometric imperfections of the flanges can be an influential factor in assessed fatigue damage over some given Fatigue Limit State load case. Schemes to analyse the effect of geometric imperfections using Finite Element Method simulations are available in literature. These schemes rely on the use of proprietary tools for the analysis. In this paper we introduce an open-source workflow to assess load transfer through geometrically imperfect bolted ring-flanges. The workflow relies on four open-source toolsets: the FreeCAD 3D parametric modelling package, the Code Aster / Salome-Meca Finite Element Method simulation environment, the ParaView post-processing and visualisation package, and the Python programming language. We present a case study of load transfer assessment in a monopile to transition piece bolted ring-flange typical of modern offshore wind turbine support structures. We decompose the load transfer across the flange under a number of geometric imperfection scenarios to determine the expected stress ranges for fatigue analysis. The results are compared with analytical methods specified in engineering standards. The workflow is configurable as per user needs, and is maintained as a GitHub repository at https://github.com/jhjorg/OpenBoltRF.
Integrated floating wind farm layout design and mooring system optimization to increase annual energy production
Authors: Mahfouz Mohammad Youssef , Lozon Ericka , Hall Matthew , Cheng Po Wen 
Published: June 2024

Abstract
As we cluster wind turbines in wind farms to gain energy from sites with high wind speeds, wake losses occur within the wind farm. Wake loss is a term used to describe the lower energy production of a downwind turbine that is totally or partially in the wake of an upwind turbine. To decrease wake losses inside the wind farm, the wind farm’s layout is optimized. However, a variety of factors constrain the wind farm layout optimization, such as the size of the lease area relative to the number of turbines to be placed, or the shape of the lease area. Therefore, many wind farms end up with a regular grid layout, such as the Horns Rev 1 wind farm in the North Sea. The ability of a floating offshore wind turbine (FOWT) to change its position based on the wind direction and its mooring system design presents an opportunity to further decrease wake losses in floating wind farms. In this work, we integrate the design of the FOWT mooring systems with the floating wind farm layout design with the goal of increasing the farm’s annual energy production. We use the Horns Rev 1 wind farm as a case study to demonstrate our method. The results show that allowing the FOWT to relocate can decrease wake losses up to 18%. Moreover, the newly developed mooring systems are less stiff and therefore allow larger motion of the FOWT; hence, the material cost of the mooring system decreases by an estimated 17%.
Fatigue assessment of a new concept for a floating barge with pendulum for offshore wind turbines in MOST
Authors: Sirigu Massimo , Ghigo Alberto , Petracca Ermando , Giorgi Giuseppe , Bracco Giovanni 
Published: June 2024

Abstract
Among floating foundations for offshore wind turbines, the barge is considered one of the most cost-effective platforms, owing to its ease of manufacturing, transport, and installation. However, the barge platform is susceptible to wave-induced stress due to its extensive waterplane area, potentially leading to fatigue in critical structural components such as the platform, tower, nacelle components and moorings. This paper delves into the prospect of mitigating fatigue damage in the barge concept by introducing a pendulum ballast, which can be installed at the offshore site using polyester ropes. The primary focus of this research is the assessment of the ‘barge-pendulum’ concept, aimed at reducing load cycles that could lead to fatigue failure, with a specific emphasis on the tower base as a representative indicator of device damage. The analysis is conducted using MOST, a time-domain simulation code developed in Matlab-Simscape environment. The findings show that the barge-pendulum concept has a poorer performance in terms of fatigue life, due to the increased sensitivity to wave forces.
Influence of wind-wave characteristics on floating wind turbine loads: A sensitivity analysis across different floating concepts
Authors: Reddy Likhitha Ramesh , Karystinou Dimitra , Milano Daniel , Walker John , Viré Axelle 
Published: June 2024

Abstract
Floating offshore wind turbines experience different operating conditions, such as wind and wave inflow characteristics. Accurate prediction of the loads acting on the floating wind system is essential for the system design and optimisation. However, there are a lot of uncertainties with the modelling input variables for time domain simulation tools such as OpenFAST to represent various hydro-aerodynamic and structural properties. The primary objective of this work is to identify the critical input parameters for different damage-equivalent load outputs for two substructure types: OC3 Hywind Spar and OC4 DeepCwind semisubmersible. The same rotor-nacelle assembly and tower (the NREL 5MW reference turbine) are used in both case studies. A sensitivity analysis based on the damage equivalent loads of six output quantities was conducted with 8 or 10 input parameters (depending on the floater). The dependent parameters were conditionally parameterised based on the independent inputs, such as wind speed and wind-wave misalignment.
The outcomes of this work show that the floater type affects the sensitivity levels of wave characteristics and hydrodynamic drag coefficients with no significant influence on the turbulence intensity, as expected. Further, the drag coefficient for spar-buoy configuration significantly influences mooring line tension compared to the semisubmersible because of their drag-dominant slender structure. The current velocity is the most dominating parameter for the mooring loads, irrespective of the floater type. While wave characteristics also influenced some turbine loads, it was almost independent of the floater type. Furthermore, the choice of the hydrodynamic model does not affect the sensitivity level rankings. A convergence study on the number of starting points was conducted to ensure a global sensitivity approach. As seen in this study, the results are floating platform-specific. This study provides valuable insight into design-driving input parameters, characterising substructure-specific wind-wave influence.
Floating Wind Farm Layout Optimization Considering Moorings and Seabed Variations
Authors: Hall Matthew , Biglu Michael , Housner Stein , Coughlan Katherine , Mahfouz Mohammad Youssef , Lozon Ericka 
Published: June 2024

Abstract
This paper presents a method for optimizing the layout of floating wind farms that accounts for realistic seabed variations and the consequent adjustments to the mooring systems required for different turbine positions. The mooring lines of floating wind farms create large spatial constraints that are depth-dependent, since mooring designs must adapt to variations in seabed conditions over the array area. We develop a layout optimization methodology that addresses this, adjusting mooring system designs based on the local seabed characteristics as the layout changes and using steady-state models for the wake effects and mooring lines. The approach includes design algorithms that adjust the anchor positions and line length to achieve the desired mooring line profile for different water depths, and a layout optimization framework that implements spatial constraints between the turbines, mooring lines, and lease area boundaries. Demonstrating the method on several cases shows the effect of the seabed and spatial-constraint factors, as well as their interactions, on the optimal array layout. This demonstration paves the way for scaling up the method, using more powerful optimization algorithms to handle larger farm sizes and situations with more intensely varied seabed conditions.
CFD analysis of local influences in offshore wind measurements employing a floating LiDAR system
Authors: Da Silva J E M , Fraga G C , Petry A P 
Published: June 2024

Abstract
In the present work, the CFD modeling of neutral and stable atmospheric boundary layers regarding the horizontal homogeneity condition is discussed to assess the impact of local influences in wind measurements made by a Light Detection and Ranging (LiDAR) remote sensor installed at an offshore site. The LiDAR will be mounted on a real floating, production, storage, and offloading (FPSO) vessel, 200 km far from the coast, and the simulations serve as preliminary study for the impact of the geometry presence, in the air flow and in the measurements taken by the LiDAR. The reproduction of the homogeneity condition is discussed and the impacts of the presence of the ship structure are quantified considering the scanning scheme of the LiDAR. Turbulence is modeled with the k-ε and k-ω models for the neutral case, and k-ε with a modification following the Monin-Obukhov Similarity Theory for the stable boundary laye. By carrying out simulations with empty and blocked (i.e., with the FPSO installed) domains, we show that the effect of the platform is local and only significant at small heights. The neutral and stable cases show similar deviations (≤ 2 %) between the velocity fields in the blocked and empty domains. The neutral case shows locally a little more impact than the stable case, and the reason for that is discussed. We also found that the LiDAR scanning scheme could attenuate the impacts of the flow distortion in comparison with direct punctual measurements.
Dragonfly-Inspired Blades for high Aerodynamic Performance small Horizontal Axis Wind Turbine
Authors: Khedr Amr , Castellani Francesco 
Published: June 2024

Abstract
Inspired from the fascinating realm of Dragonfly features, this study intricately investigates the aerodynamic performance of a distinctive 1 m diameter small-scale Horizontal Axis Wind Turbine characterized by a unique bio-inspired tandem-blades configuration. Based on experimental wind tunnel tests and computational fluid dynamics simulations, the turbine performance is explored at different Tip Speed Ratios (TSRs). Remarkably, the bio-inspired turbine exhibits exceptional traits, achieving a notable peak power coefficient of approximately 0.35 at a low TSR of 3. A detailed investigation includes thorough analyses of pressure contours, relative velocity distributions, and individual blade contributions, revealing unique dynamics within the tandem configuration. The fore blade notably prevails in extracting wind energy, showcasing superior performance. While the hind blade influence in enhancing the fore blade efficiency emerges, underscoring the role of blade interactions in this bio-inspired designs. This study contributes significantly to the comprehension of the new design dragonfly-inspired wind turbine aerodynamics.
Given a wingspan, which windplane design maximizes power?
Authors: Trevisi Filippo , Croce Alessandro 
Published: June 2024

Abstract
Windplanes (i.e. Fly-Gen airborne wind energy systems) harvest wind power via the turbines placed on the tethered wing, which flies crosswind trajectories. In this paper, the optimal design of windplanes is investigated with simplified models, enabling an intuitive understanding of their physical characteristics. The windplane is then idealized as a point mass flying circular fully crosswind trajectories. If the gravity is neglected, the dynamic problem is axial symmetric and the solution is steady. The generated power can be expressed in non-dimensional form by normalizing it with the wind power passing by a disk with radius the wingspan. Since the reference area is taken to be a function of just the wingspan, looking for the design which maximizes this power coefficient addresses the question ”Given a wingspan, which design maximizes power?”. This is different from the literature, where the design problem is formulated per wing area and not per wingspan. The optimal designs have a finite aspect ratio and operate at the maximum lift-to-drag ratio of the airfoil. Airfoils maximizing the lift-to-drag ratio are then optimal for windplanes. If gravity is included in the model, gravitational potential energy is being exchanged over one revolution. Since this exchange comes with an associated efficiency, the plane mass and the related trajectory radius are designed to reduce the potential energy fluctuating over the loop. However, for decreasing turning radii, the available wind power decreases because the windplane sweeps a lower area. For these two conflicting reasons, the optimal mass is finite.
On the underperformance of the full-scale Clarkson University 3 meter ducted turbine
Authors: Visser Kenneth D 
Published: June 2024

Abstract
The performance of the Clarkson University 3 meter wind turbine under ambient conditions was measured to be considerably below that observed from the initial wind tunnel data. Comparison is made of the tunnel results with data obtained at three different experimental test sites and two different electronic downstream configurations. It is suggested that the advantages of the duct are mitigated by the transient nature of the ambient wind velocity and a required minimum rotational speed is needed to develop a sufficient thrust coefficient at the rotor plane for the duct to operate effectively. In the absence of these conditions, the presence of the duct can be argued to diminish the turbine performance.
Machine learning to rapidly predict turbine yaw angles for wake steering
Authors: Stanley Andrew P. J. , Mulder Tim , Doekemeijer Bart , Kreeft Jasper 
Published: June 2024

Abstract
Wake steering is an important control strategy to boost power production of a wind farm. Because of computational expense and problem complexity, wind farm layouts are typically optimized assuming they will operate without wake steering. However, performance gains are possible by simultaneously optimizing wind farm layout and the yaw angles for wake steering. In this paper, we present a method to train a machine learning model to predict turbine yaw angles as a function of their position relative to other turbines in the wind farm and the inflow wind speed. This model is able to predict turbine yaw angles with an R2 value of 0.98. The model also produces turbine yaw angles with wind farm power production that is similar to yaw angles that have been directly optimized. This method to rapidly compute optimal turbine yaw angles for wake steering enables control co-design of wind farms and the associated performance increase.
Control Co-Design Studies for a 22 MW Semisubmersible Floating Wind Turbine Platform
Authors: Zalkind Daniel , Bortolotti Pietro 
Published: June 2024

Abstract
We present a control co-design software framework that can be used to optimize floating wind turbines and their controllers. Because this framework has many options for design variables, constraints, and merit figures, along with modeling fidelity levels, we seek to demonstrate best practices for using the tool while designing a floating platform for the new 22 MW offshore reference wind turbine developed within the International Energy Agency Wind Technology Commercialization Programme 55 on Reference Wind Turbines and Farms. During these studies, we evaluate the use of different simulation fidelity levels, the effect of using different load cases for controller tuning, and the difference between sequential and simultaneous control co-design solutions. Based on these efforts, we suggest using an algorithm that performs an initial search of the design space before optimization. We find that solving smaller optimization problems, in a sequential manner, leads to more reliable outcomes in fewer iterations than larger, simultaneous control co-design solutions. However a simultaneous CCD solution produces a platform with a 2% lower mass than the sequential CCD outcome.
Aerodynamic and production comparison of wind farms with downwind versus conventional upwind turbines
Authors: Frontin Cory , Vijayakumar Ganesh , Bortolotti Pietro 
Published: June 2024

Abstract
Ever-increasing turbine scales and their associated logistical challenges have reignited questions about the performance of downwind rotor configurations. A particular potential benefit of downwind rotor configurations is the farm-scale power increase that may be conferred by tilt-driven downward wake entrainment and associated wake recovery. In this work, a comprehensive aerodynamic analysis is carried out to understand the mechanisms for wake entrainment and recovery across a spectrum of velocity and inflow alignment conditions on a small, structured farm in order to understand the impact of downwind rotors on farm production. The results show that the benefits demonstrated previously in the literature for downwind-rotor farms in aligned flows are fragile, and, outside of strong farm/flow alignment conditions, power production benefits for small farms with downwind rotor configurations are significantly if not completely mitigated by misalignment effects. The work indicates that farm-scale benefits for downwind rotors must be realized either from large-scale entrainment benefits, with more exotic farm arrangements that can take advantage of the aerodynamic effects, or from beneficial fatigue impacts from entrainment of less turbulent outer boundary layer flows.
Wake Effect Quantification using SCADA Data and LES Modelling of an Operational Offshore Wind Farm
Authors: Chanprasert Warit , Sharma Rajnish N. , Cater John E. , Norris Stuart E. 
Published: June 2024

Abstract
Wake effects in the Anholt offshore wind farm have been investigated using both operational data and a Large Eddy Simulation (LES) model of a group of five turbines within the wind farm. Analysis of operational data showed that the variations of main shaft speeds of the downstream turbines were almost six times those of the upstream turbine at near-rated operation. The aim of the LES was to study the impact of atmospheric stability on the wind turbine array performance and compare this with the field data. An LES precursor method was used to model the near-neutral and unstably stratified atmospheric boundary layers that represent typical conditions in winter and summer, respectively, and the turbines in wind farm model were simulated using an actuator line method. It was found that LES with the actuator line method and generic turbine design data can generate a reasonable mean power generation trend for the Anholt wind farm under near-neutral and unstable conditions. The maximum difference in the mean power output between the LES and averaged operational data was approximately 20%.
Reconstruction of dynamic wind turbine wake flow fields from virtual Lidar measurements via physics-informed neural networks
Authors: Zhang Jincheng , Zhao Xiaowei 
Published: June 2024

Abstract
Accurate characterisation of wind turbine wakes is important for the optimal design and operation of wind farms. However, current techniques for full-scale wind measurements are still limited to point characterisation. To address the research challenge in obtaining field characterisation of real-world wind turbine wakes, this work investigates the reconstruction of the dynamic wake flow fields based on a virtual turbine-mounted Lidar and physics-informed neural networks. Specifically, the wake flow field is reconstructed by fusing the sparse measurements with the two-dimensional Navier-Stokes equations without imposing any models for the unsteady wake. Different from supervised machine learning approaches which need the measured values for the quantities of interest in the first place, the proposed method can achieve the prediction of the wind velocity at new locations where there is no measurement available. The reconstruction performance is evaluated via high-fidelity numerical experiments and it is shown that the dynamic wind turbine wake flow fields are predicted accurately, where the main wake features, including the downwind development and crosswind meandering of the wake, are both captured. This work thus paves the way for investigating full-scale in situ wake flow dynamics in real-world wind energy sites.