bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lidar-based virtual load sensors for mooring lines using artificial neural networks
Authors: Gräfe Moritz , Özinan Umut , Cheng Po Wen 
Published: November 2023

Abstract
Floating offshore wind turbines are equipped with a variety of sensors, which are measuring data, valuable for the control and monitoring of the turbine. However, reliable measurements are difficult or costly for some physical quantities. This includes load estimates for mooring lines and fairleads. In this study, we investigate an approach using wind speed measurements from a forward-looking nacelle-based lidar as inputs to long short-term memory networks to estimate fairlead tensions. Nacelle-based lidar wind speed measurements on floating offshore wind turbines are influenced by platform motions, in particular by the rotational pitch displacement and the surge displacement of the floater. Therefore, the lidar wind speed measurement contains information about the dynamic behavior of the floater. In turn, the floater’s dynamics determine the fair lead loads. Thus in this study, we directly use the lidar-measured line of sight (LOS) wind speeds to estimate mooring line tensions. The model training data is obtained using the aero-elastic wind turbine simulation tool openFAST in combination with the numerical lidar simulation framework ViConDAR. Results show, that lidar-based virtual load sensors can reproduce mean fairlead tension as well as low-frequency fluctuations, with varying accuracy dependant on the combination of input features. For the model which is only using LOS wind speed measurements as input a normalized root mean squared error of 0.55 was obtained.
Development of a risk analysis model for the installation of offshore wind farms
Authors: Munoz N Garcia , Lange AK , Kaczenski J , Wiggert M 
Published: November 2023

Abstract
The installation of offshore wind farms represents a major driver of offshore wind energy costs due to the high level of associated risks. Substantial cost reduction potential can be realized if these risks are effectively identified and controlled, preventing project delays and financial damages. Therefore, we propose a new method to identify, analyse and evaluate installation risks for use in project planning. This paper provides an in-depth walkthrough of the steps involved in the development of a simulation-based quantitative risk analysis model. At the example of a turbine installation case study, project plan-related risks are identified and quantified by conducting a literature review and expert interviews. The corresponding risk likelihoods and consequences are modelled with probability distributions to simulate their impact on total project duration. Using Monte Carlo simulation, the distribution of results is statistically evaluated to derive the expected project delay caused by the analysed risks as well as reference values for optimistic and pessimistic scenarios. Regarding the underlying model assumptions, the most significant risks (e.g. supply chain failure) are identified and examined in a sensitivity analysis. The developed model can serve as a basis for developing more reliable schedule estimations and contribute to minimizing installation delays and costs.
Quick assessment of semi-submersible floating offshore wind turbines under misaligned wind, wind-wave and swell-wave loading
Authors: van der Spek J B , Maljaars N , Shen Q , Grammatikopoulos A 
Published: November 2023

Abstract
Computer-intensive coupled time-domain simulations are used by both academia and industry to capture the nonlinear behavior of floating offshore wind turbines. To assist in pre-design and optimization, computationally efficient methods such as frequency-domain methods are required. However, state-of-the-art frequency-domain methods consider simplified cases which do not represent operational design cases of industry projects. This paper compares the effectiveness of a frequency-domain method based on Response Amplitudes of Floating Turbines (developed by the NREL) to time-domain simulations carried out in BHawC-OrcaFlex by Siemens Gamesa Renewable Energy. The load cases are part of IEC Design Load Case 1.2 (fatigue in normal power production) and are selected from an industry project. Reasonable agreement is found for the pitch/roll rigid body modes around rated wind speed. However, the mean response and dynamic response is overestimated by the frequency-domain method due to underestimation of the mooring stiffness and the underestimation of hydrodynamic damping. For the estimation of the fore-aft and side-to-side bending moment, main differences are identified due to the absence of the tower bending, excitation due to rotor rotation and second-order wave forcing in the frequency-domain method. The results show the need for extending the frequency-domain method with tower bending and rotor rotation as degrees of freedom.
Rational Simplification of High Fidelity Wind Turbine Models Used for Mooring Analysis
Authors: Kvittem Marit I , Fredriksen Arnt G , Souza Carlos S de , Hanssen Finn-Christian W 
Published: November 2023

Abstract
This study investigates the use of simplified turbine modelling in analysis of a soft mooring system (horizontal plane periods > 250 s). Two simplified turbine models are developed, tested and compared to a high fidelity turbine model in a case study of the INO WINDMOOR 12 MW FOWT with a soft mooring system. The chosen simplified modelling strategies are a drag disc model, a de-coupled approach where the aerodynamic loads are pre-calculated in a fixed turbine simulation and a model with reduced degrees-of-freedom. Corrections to the pre-calculated force model is also developed and compared. The results show that the pre-calculated force approach gives better comparisons to the full model than the drag disc model, and that applying a controller correction to account for the wind turbine controller’s response to floater motions improves the predicted response.
A passively self-adjusting floating wind farm layout to increase the energy production: a sensitivity analysis
Authors: Mahfouz Mohammad Youssef , Cheng Po Wen 
Published: November 2023

Abstract
Offshore wind farm layout design techniques and methodologies currently focus on fixed bottom offshore wind turbines. As more floating wind farm (FWFs) are planned, new methodologies for FWF layout design and optimization are required to consider the different attributes between fixed bottom and floating offshore wind turbines (FOWTs). One main difference is the ability of FOWTs to move in the horizontal plane (surge and sway motions). In our work in [1], we showed that the motions of the FOWTs in the horizontal plane represent an opportunity which can be used to increase the FWF’s annual energy production (AEP). We can passively control the motions of the FOWTs in a FWF according to the incoming wind direction, moving the downwind turbines out of the wake of upwind ones. Since the horizontal motions of a FOWT are governed by the mooring system design (MSD) attached to it, this passive control can be done by designing a customized mooring system (MS) for every FOWT in the farm. In this work we build on our work in [1], as we carry out a sensitivity analysis to check the effect of the farm size and the wind rose on the methodology we introduced. The results show that the percentage increase of energy production due to passively relocating the FOWT is sensitive to the FWF size. Very small FWFs will gain less energy by relocating the FOWTs. Moreover, we show that even with a more uni-directional wind rose relocating the FOWTs in a FWF remains beneficial.
Layout and yaw optimisation of an offshore wind farm through analytical modelling
Authors: Sukhman D , Lück S , Göing J , Bartl J , Hansen T , Stenfelt G , Friedrichs J 
Published: November 2023

Abstract
In this work, a computational tool for analytical large scale modelling of offshore wind farms is presented. Using Horns Rev 1 as a reference baseline, an optimal layout and yaw angle setting for one wind direction based on aerodynamic considerations is proposed. Based on a wake model presented by Qian & Ishihara, flow velocities as well as turbulence intensities are predicted when several wake flows are superimposed. Subsequently, the aerodynamic performance of the wind turbines is calculated. The proposed tool shows good agreement with measurement and LES data. The influence of performance-driving parameters, namely turbine spacing, ambient turbulence intensity and yaw angle are investigated. The axial spacing and ambient turbulence are identified as the most significant factors. Based on these results, the proposed optimal layout solution suggests a higher power yield of up to 57 %, while the optimal yaw angles found in this work show a power increase of over 6% compared to the baseline layout.
Wind tunnel hardware-in-the-loop experiments about the global response of a 15 MW floating wind turbine
Authors: Fontanella A. , Facchinetti A. , Belloli M. 
Published: November 2023

Abstract
This work describes a new wind tunnel hybrid experiment investigating the aerodynamics and the global response of a 15 MW floating wind turbine. The floater motion is realized with a 6-degrees-of-freedom robotic platform controlled with a hardware-in-the-loop system, in which aerodynamic forces developed by the turbine model are the input of a numerical simulation of the floater dynamics, hydrodynamic excitation, and mooring. It is shown that accuracy of the aerodynamic force feedback from the wind turbine is critical to reproduce the floating wind turbine motion, and measurement of aerodynamic loads is more uncertain in case of pitch motion that movement in the other directions. Free decay tests show that damping of platform surge, pitch, and yaw modes is increased with wind and operating wind turbine compared to the no wind case. The effect of aerodynamic loads on the platform response with stochastic waves is small in the wave frequency range, whereas response of the surge mode is increased with wind.
Validation of a panel method with full-scale FOWT measurements and verification with engineering models
Authors: Netzband Stefan , Schulz Christian W , Özinan Umut , Adam Raphaël , Choisnet Thomas , Cheng Po Wen , Abdel-Maksoud Moustafa 
Published: November 2023

Abstract
The present paper gives insights into the verification of different models of the Floatgen demonstrator by BW Ideol. This floating offshore wind turbine (FOWT) is based on a barge type-floater with moonpool. The moonpool shall dampen the platform’s motion and is challenging to model due to the increased complexity of the hydrodynamic behaviour. For the verification purposes, the results of two engineering methods (OrcaFlex, OpenFAST) equipped with frequency-dependent hydrodynamic solver and the nonlinear time-domain boundary element method panMARE are compared. The OrcaFlex model designed by BW Ideol is regarded as a reference because of a preceding calibration with measurement data. All models show fairly good agreement in most cases. Only in heave there are significant differences between engineering and the nonlinear models which is caused by different modelling of the moonpool hydrodynamics. In addition, a hybrid simulation approach with prescribed motion and constrained wind field based on motion sensors and LIDAR measurements on the Floatgen demonstrator was applied for an aerodynamic and load validation of panMARE. The validation shows good agreement based on time-domain comparison regarding the tower top loads and turbine operation.
The Impact of Unsteadiness on the Aerodynamic Loads of a Floating Offshore Wind Turbine
Authors: Schulz Christian W. , Özinan Umut , Netzband Stefan , Cheng Po Wen , Abdel-Maksoud Moustafa 
Published: November 2023

Abstract
The role of unsteadiness in the aerodynamics of Floating Offshore Wind Turbines (FOWT) remains a subject of discussion among the research community. Therefore, it must be investigated whether and to what extent transient aerodynamic phenomena impact the loads of a wind turbine rotor undergoing motions in unsteady winds. The study of transient aerodynamic phenomena is closely linked to the question of whether the modern Blade Element Momentum Theory (BEMT) methods can be considered reliable for the simulation of FOWTs. In this work, investigations are carried out to identify the relevant transient aerodynamic phenomena and quantify their effects on the torque and thrust of the Floatgen wind turbine. A free-wake panel method is utilised to identify and quantify transient parts of the load response to a set of simplified unsteady scenarios: a wind gust, a harmonic surge motion and a rotor speed oscillation. Transient contributions to the load behaviour of the wind turbine can be identified in all scenarios under consideration. In addition, the ability of a state-of-the-art BEMT method to model the identified transient contributions is evaluated. While an agreement of the qualitative impact of the transient aerodynamic phenomena at moderate motion frequencies is found, a contradicting behaviour of the simulation models becomes apparent at high motion frequencies. This indicates the presence of a transient, three-dimensional wake effect that cannot be reproduced by the common unsteady corrections for BEMT methods.
Validation of a potential flow-based numerical model for engineering design of Floating Offshore Wind Turbine foundations
Authors: Tomaselli P D , Jensen B 
Published: November 2023

Abstract
Designers apply numerical models for scrutinizing the complex response of Floating Offshore Wind Turbine (FOWT) foundations to environmental conditions at sea. This paper presents a numerical model for predicting the wave-induced motions of FOWT foundations. The model combines two solvers, one for generating the forcing wave field and the other for computing the foundation response based on Potential Flow Theory. With its robustness and relatively low computational demand, the proposed model aims to assist the initial exploratory stages of the FOWT design process. A validation of the proposed model against a laboratory experimental campaign is presented. The performance of the model is investigated, with highlighting the role of second-order hydrodynamic effects such as viscous damping and slow-drift.
A control-oriented model for floating wind turbine stability and performance analysis
Authors: Pegalajar-Jurado Antonio , Lio Alan W.H. 
Published: November 2023

Abstract
A well-designed floating turbine controller should lead to small power fluctuations while keeping the system stable. Floating wind turbines can experience instability when operating above rated wind speed, due to the blade pitch controller. This phenomenon, known as negative aerodynamic damping, is the reason why a controller needs to be re-designed for floating applications. One solution is to de-tune the blade pitch controller and make it slower than the floater pitch motion. This solution, although simple, reduces the controller’s ability to react to changes in the inflow and results in large power fluctuations. A more sophisticated approach involves an additional loop feeding back the fore-aft nacelle velocity to the blade pitch or generator torque. The choice of gains, however, is not trivial. This work proposes a control-oriented model derived from first principles to investigate different controller configurations in terms of both stability and turbine performance. The linear model with seven degrees of freedom (six rigid-body motions and drivetrain) is formulated analytically and coupled with the controller. The linear formulation allows us to investigate stability via eigenvalue analysis and performance via frequency-domain response, thus bypassing the need for time-domain simulations. Parametric studies with thousands of different controller configurations can be completed in a matter of minutes.
Thermoelectric properties of metashale geopolymer mortar doped with graphite powder
Authors: Hotěk Petr , Fiala Lukáš , Černý Robert 
Published: November 2023

Abstract
Building materials with favorable thermoelectric properties can become a supplementary source of clean energy due to their ability to convert waste heat into electric energy. Depending on the thermoelectric conversion effectivity defined by the Seebeck coefficient, constructions made of these materials can serve as civil engineering energy harvesters. Since the conversion effectivity of common calcium(alumino)silicates (cementitious materials, geopolymers) is low, doping with electrically conductive admixtures is a crucial step to handle the issue. The paper is focused on the design of metashale mortar doped with graphite powder (3 wt.%), determination of its common material properties, as well as experimental determination of thermoelectric properties. The maximum thermoelectric voltage (161.65 mV, ΔT = 130 °C), Seebeck coefficient (538 μV K-1), and figure of merit (∼ 10-9) revealed significantly better thermoelectric performance than cement pastes or alkali-activated slags doped with multi-walled carbon nanotubes and if of promising thermoelectric conversion potential.
Physical properties of alkali activated aluminosilicates based on low-reactivity ceramics in room temperature conditions
Authors: Keppert M , Pommer V , Šádková K , Vejmelková E , Černý R 
Published: November 2023

Abstract
Alkali activated aluminosilicates (AAA), or geopolymers, are widely studied materials because they are supposed to become a more sustainable alternative to materials based on Portland cement, such is especially concrete. AAA materials are generally produced by activation of an aluminosilicate precursor by an alkaline solution – usually solution of sodium silicate and sodium hydroxide. The capability of the prepared material to be used as construction material is commonly evaluated by means of its compressive strength. The present paper aims to broaden the AAA materials characterization to other physical properties such are porosity and thermal conductivity, since these measures are closely related to the engineering performance of the material. The waste ceramic dust was used as precursor while the solution of potassium silicate was an activator. The relationships between the above listed physical properties and obviously on the material composition were searched.
Deterioration of basalt-based reinforcement in corrosive environments: experimental monitoring and mathematical models
Authors: Kočí V , Keppert M , Černý R. 
Published: November 2023

Abstract
The basalt-based reinforcing elements are considered as alternative to conventional steel-based reinforcing elements (rebars, wires). The motivation to use basalt-based elements (fibers, composite bars, meshes etc.) is better corrosion resistance of basalt fibers especially in sea-water environment, compared to carbon steel. Nevertheless, it does not mean that basalt fibers are 100% corrosion resistant. The basalt fibers are produced from silicate melt of proper composition, i.e. the basalt fibers are vulnerable to both acid and alkaline hydrolysis, as well as other silicates do. When basalt fibers are used as reinforcement in concrete, the alkaline hydrolysis will become an important issue. The present paper deals with experimental observation of basalt fibers in alkaline environment of Simulated Pore Solution. The fibers deterioration was monitored by their mass loss and SEM microscopy. Jander’s model was used to describe mathematically the kinetics of the fibers alkaline hydrolysis. The results revealed that a corrosion products layer is formed on the fibers surface in this environment. The composition of this layer corresponds to N-A-S-H and C-A-S-H phases known from alkali-activated aluminosilicates or hydrated Portland cement.
Evaluation of transient measurements of thermophysical parameters using Finite Elements Method.
Authors: Malinarič S 
Published: November 2023

Abstract
The transient plane source (TPS) method was used to measure the thermal diffusivity and conductivity of silica glass and polymethyl methacrylate (PMMA). The results were evaluated by an analytical model and also by a numerical model created by the finite elements method (FEM). The results of both models and both materials were compared, and the difference was less than 0.4%.
Study of the illite-kaolinite-CaCO3 mixtures during firing
Authors: Mikušová D , Húlan T , Lukáč F , Csáki Š , Trník A 
Published: November 2023

Abstract
The raw materials used in traditional ceramics include highly plastic clay minerals such as illite or kaolinite. Non-plastic materials are usually added to the mixtures, which affect their workability and sintering process. The formation of a new crystalline phase (e.g. anorthite) is often observed in mixtures that contain a large amount of CaO. The improvement of final properties of ceramic materials is attributed to the formation of anorthite. The aim of this paper is to study the firing of anorthite ceramics in the system illite-kaolinite-CaCO3. Four sets of samples with different illite:kaolinite ratio (8:2, 6:4, 4:6, 2:8), and with a constant addition of CaCO3 are produced. The samples were subjected to the thermal and structural analyses. A significant mass loss is observed for all studied samples during the process of dehydroxylation and decomposition of CaCO3. An exothermic peak around 950 °C, which is connected with the formation of anorthite, is observed during differential thermal analysis. Above this temperature, no significant length changes are recorded. The presence of anorthite is confirmed by XRD analysis. The most formation of anorthite is observed in the illite-kaolinite sample with ratio 8:2.
Laboratory synthesis of C3A on the kilogram scale: Preliminary results
Authors: Scheinherrová L , Krejsová J , Beneš M , Šteffek M , Černý R 
Published: November 2023

Abstract
This paper focuses on tricalcium aluminate (C3A) synthesis on the kilogram scale in laboratory conditions. The proposed design aims to produce more than 97 wt% of C3A. The remaining three wt% could be associated with residual lime, CaO, which is preferable over mayenite (C12A7). The maximally used temperatures for the synthesis were 1350 °C and the borderline temperature of 1400 °C, beyond which C3A and liquid phase can be formed. The preliminary results showed that using the CaO:Al2O3 ratio of 62.5:37.5 and a temperature of 1400 °C, it was possible to achieve pure cubic C3A of the desired quality. Moreover, it was shown that the time for which was the maximal temperature kept before removing the samples from the furnace was an essential parameter that influenced most significantly the amount of mayenite in the structure of C3A.
Calibration of microwave antenna for porous materials moisture evaluation using frequency domain analysis
Authors: Tabiś K , Suchorab Z , Szczepaniak Z , Majerek D , Rogala T , Knioła M , Susek W 
Published: November 2023

Abstract
The article presents the possibility to use microwave contactless measuring system for evaluation of moisture of porous media, mainly building materials utilizing the frequency domain analysis. In the article the description of microwave sensing technique is presented and the methods of microwave data analysis described. In the second part of the manuscript, microwave readouts are presented and the apparent permittivity values estimated in the red brick samples depending on moisture. With the calculated data, calibration model is estimated and fitting quality evaluated. Using the achieved data and calculated values the potential of microwave sensing technique is evaluated and advantages and disadvantages presented.