1,138 research outputs found
An experimental study on trailing edge crack detection for wind turbine blade using airfoil aerodynamic noise
No full textRecent decades have witnessed more and more wind turbines (WTs) being installed onshore and offshore. Health condition monitoring for WTs structures and components is increasingly becoming a compelling concern for stable power output and operational safety of a wind farm [1]. Blade damages seem to occur with a higher probability ahead of other components (e.g., gearbox and generator) damages [2]. After reviewing traditional damage detection approaches and their limitations [3], in this research a new non-contactable approach to detecting trailing edge (TE) damages is proposed based on airfoil aerodynamic noise measurements using a microphone array. In the experiment, four changeable TE parts with rectangular cracks (damaged width W of 0.2mm, 0.5mm, 1.0mm and 2.0mm) for a NACA0018 airfoil (chord C=200mm, span L=400mm) are designed and an example with W=0.2mm is shown in Fig.(a). The TEs with cracks have the same solid thickness as the baseline one (h_solid=0.76mm, standard NACA0018 airfoil TE thickness with chord of 200mm) but different dimensions of total TE thickness (h=W+h_solid). A phased microphone array with 64 microphones is used for acoustic measurement then beamforming is applied to extract TE noise and source power integration is performed within a 200×200mm2 region centred at TE midpoint [4][5]. Fig.(b) shows sound pressure levels (SPLs) L_p at the integrated region of four damaged cases as well as baseline with the frequency resolution of 10Hz under the freestream velocity U of 35m/s and geometrical angle of attack (AoA) alpha of 0º. The cases with smaller cracks show less remarkable tonal peaks compared with the one of W=2.0mm (~4dB); when the crack size is smaller the spectral peak broadens. These peaks or humps are attributed to the periodic vortex shedding from blunt TEs. Fig.(c) shows the SPL differences Delta L_p between the damaged cases and baseline; frequency is normalized as TE-thickness-based Strouhal number St. Local maxima of Lp are present at approximately St = 0.1 [6]. In the experiment, it is difficult to extract the spectral peaks or humps if the effective AoA (alpha*) [6] is more than 2.40º because the boundary layer on suction side becomes thicker and the asymmetry of boundary layers prevents coherent and periodic vortex shedding [7]. In Fig.(d), the discrete points are the St at peak L_p (St_peak) versus the ratio of TE thickness and averaged displacement thickness of pressure and suction sides (overline delta *) extracted from available cases (U=15m/s, 20m/s, 25m/s, 30m/s and 35m/s); the grey and blue curves are obtained from models reported in [6] with solid angle (Psi) of 20º and 23.76º (baseline solid angle), respectively. The points of St_peak versus thickness ratio show a good agreement with the prediction model [6]. This means that particularly for smaller cracks at the first stage of damaged process, the effect of solid angle can be neglected and considered as a minor and adjunctive factor. The TE thickness retrieved through the application of the model can be used as a prediction of the damage level. Additional data obtained from experiments with turbulent inflow will be presented to assess if the approach proposed is still feasible in more realistic turbulent inflow conditions. Keywords: wind turbine blade; trailing edge crack; damage detection; aerodynamic noise. Images: Link: https://s3-eu-west-1.amazonaws.com/static.vcongress.de/cms/forwind/paper/417dd783-7a7c-424d-a4d3- 55ce31fa41e1.png Description: (a) An example of NACA0018 airfoil with a TE crack of 0.2mm. (b) SPLs with resolution of 10Hz (U=35m/s and alpha=0º). (c) Corresponding SPL differences compared with baseline case normalized as peak St. (d) Relations of peak St and thickness ratio: discrete points are the experimental date; grey and black curves are prediction models Brooks et al. proposed with solid angle of 20º and 23.76º. References: [1] Tautz-Weinert, J. and Watson, S.J., 2016. Using SCADA data for wind turbine condition monitoring–a review. IET Renewable Power Generation, 11(4), pp.382-394. [2] Yang, W., Peng, Z., Wei, K. and Tian, W., 2016. Structural health monitoring of composite wind turbine blades: challenges, issues and potential solutions. IET Renewable Power Generation, 11(4), pp.411-416. [3] Du, Y., Zhou, S., Jing, X., Peng, Y., Wu, H. and Kwok, N., 2020. Damage detection techniques for wind turbine blades: A review. Mechanical Systems and Signal Processing, 141, p.106445. [4] Merino-Martínez, R., Carpio, A.R., Pereira, L.T.L., van Herk, S., Avallone, F., Ragni, D. and Kotsonis, M., 2020. Aeroacoustic design and characterization of the 3D-printed, open-jet, anechoic wind tunnel of Delft University of Technology. Applied Acoustics, 170, p.107504. [5] Carpio, A.R., Avallone, F., Ragni, D., Snellen, M. and van der Zwaag, S., 2020. Quantitative criteria to design optimal permeable trailing edges for noise abatement. Journal of Sound and Vibration, 485, p.115596. [6] Brooks, T.F., Pope, D.S. and Marcolini, M.A., 1989. Airfoil self-noise and prediction. [7] Moreau, D.J. and Doolan, C.J., 2016. Tonal noise production from a wall-mounted finite airfoil. Journal of Sound and Vibration, 363, pp.199-224
The claim of humanity in Christ : salvation and sanctification in the theology of T.F. and J.B. Torrance
No full textThis thesis critically engages with the Torrances’ claim that all of humanity is in Christ. It explores how God has claimed humanity in salvation and the claim that He has placed upon humanity in sanctification. It argues that this claim upon humanity is not a cumbersome one, for God’s radically objective act of salvation is the basis for the subjective outworking of the Christian life. As we freely participate by the Spirit in the incarnate Son’s filial relationship with the Father, we grow into the ontological reality of who we are in Christ.
Part One critically examines how the salvation wrought for us by the triune God of grace is filial, ontological and objective. It challenges soteriologies that have an overarching federal or external framework which lead to people being thrown back upon their own subjective endeavours to gain salvation. Part Two extends the implications of the Torrances’ soteriology to the outworking of our sanctification. It roots sanctification objectively with
justification in Christ, challenging the belief that, having been justified by God, it is now our part to work out our own sanctification; Affirming humanity’s new eschatological orientation in the risen humanity of Christ, it argues for confidence in the nature of our humanity and in the outworking of sanctification. Thus it challenges external paradigms that can only offer a poor perspective on humanity and demand our own ineffectual efforts. It presents the outworking of sanctification in dynamic, relational terms, rather than static, moralistic terms, as the free gift of participating by the Spirit in the Son’s
intimate communion with the Father
Microscopia confocale a fluorescenza: effetti della pressione pulpare sull'interfaccia adesiva
No full textI moderni sistemi adesivi monocomponente mostrano una riduzione di adesione quando applicati sotto l'effetto di pressione pulpare simulata. Lo scopo di questo studio è stato dimostrare, tramite l'utilizzo della Microscopia Confocale a Fluorescenza, come la pressione pulpare influenza l'interfaccia adesiva di un sistema all-in-one
Influência de materiais restauradores liberadores de flúor na evolução de lesões de cárie em esmalte de molares decíduos: estudo in vitro
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde, Curso de Pós-Graduação em Odontologia.O objetivo deste estudo foi avaliar a influência de materiais restauradores liberadores de flúor na evolução de lesões de cárie em esmalte, quando aplicados em molares decíduos e submetidos a uma situação de alto desafio cariogênico. Os resultados sugerem que os cimentos de ionômero de vidro oferecem maior resistência à lesão de cárie secundária que a resina composta modificada por poliácidos e o amálgama
Book Review
No full text Pickard's Manual of Operative Dentistry, 8th edn. By E.A.M. Kidd, B.G.N.Smith and T.F. Watson. Oxford Medical Publications, Oxford University Press, Oxford, 2003 (209pp., £35.00). ISBN 0-19-850928-6. </jats:p
Influence of air-abrasion executed with polyacrylic acid-Bioglass 45S5 on the bonding performance of a resin-modified glass ionomer cement.
No full textThe aim of this study was to test the microtensile bond strength (μTBS), after 6 months of storage in PBS, of a resin-modified glass ionomer cement (RMGIC) bonded to dentine pretreated with Bioglass 45S5 (BAG) using various etching and air-abrasion techniques. The RMGIC (GC Fuji II LC) was applied onto differently treated dentine surfaces followed by light curing for 30 s. The specimens were cut into matchsticks with cross-sectional areas of 0.9 mm(2). The μTBS of the specimens was measured after 24 h or 6 months of storage in PBS and the results were statistically analysed using two-way anova and the Student-Newman-Keuls test (α = 0.05). Further RMCGIC-bonded dentine specimens were used for interfacial characterization, micropermeability, and nanoleakage analyses by confocal microscopy. The RMGIC-dentine interface layer showed no water absorption after 6 months of storage in PBS except for the interdiffusion layer of the silicon carbide (SiC)-abraded/polyacrylic acid (PAA)-etched bonded dentine. The RMGIC applied onto dentine air-abraded with BAG/H(2)O only or with BAG/PAA-fluid followed by etching procedures (10% PAA gel) showed no statistically significant reduction in μTBS after 6 months of storage in PBS. The abrasion procedures performed using BAG in combination with PAA might be a suitable strategy to enhance the bonding durability and the healing ability of RMGIC bonded to dentine
PERMEABILITA' E DEGRADAZIONE IDROLITICA DEI SISTEMI ADESIVI TOTAL-ETCH SOTTO PRESSIONE PULPARE SIMULATA
No full textCorrection to : Cost-Effectiveness of Parent–Child Interaction Therapy in Clinics versus Homes : Client, Provider, Administrator, and Overall Perspectives (Journal of Child and Family Studies, (2018), 27, 10, (3329-3344), 10.1007/s10826-018-1159-4)
No full textThe original version of this article unfortunately contained a mistake. The Author contributions section currently states: “A.F.: designed and conducted data analyses for this study, supervised by B.Y. with input by T.F. A.F. and T.F. assisted B.Y. in writing and revising the manuscript.” In fact, B.Y. and T.F. assisted A.F. in writing and revising the manuscript. Although T.F. and B.Y. were both involved in the writing, primary credit should go to A.F. (Alexis French, the first author). The authorship order above is accurate.</p
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