2,956 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
Authors' attitudes to, and awareness and use of, a university institutional repository.
No full textThis article reports the findings of an author study at Cranfield University. The study investigated authors' publishing behaviours, attitudes, concerns, and their awareness and use of their institutional repository (IR), Cranfield QUEprints. The findings suggest that despite a reasonable amount of advocacy many authors had not heard of QUEprints and were not aware of its purpose. Once explained, all authors saw at least one benefit to depositing a copy of their work to QUEprints, but many were unsure how to deposit, preferring to depend on the Library to do the work. The authors voiced few concerns or conditions regarding the inclusion of their work in QUEprints, but felt that it would be an extra, inconvenient step in their workload. This research led to the development of the Embed Project which is investigating how to embed the IR into the research process and thereby encourage more authors to deposit their work
Dr. Edwin Wright Collection: Jessica B. Watson (nee Segers)
No full textNotes - Mrs. Jessica B. Watson writes about her family life in Athabasca. Her father, Captain F. S. Segers, worked for the Hudson's Bay Company and was "in charge of all of the boat transportation up and down the river." Mrs. Watson speaks of travelling, pets, entertainment, and daily life in Athabasca, where she arrived ,via stagecoach and buckboard, when she was 16 years old, in 1891 (1 page
Developing sustainable pedagogic strategies for the international and cultural aspects of learning in art and design post-graduate education
No full textThis paper offers practical and theoretical insights into developing sustainable pedagogic strategies for the international and cultural aspects of learning in art and design post-graduate education. It builds on current research by the authors in tackling core cultural issues, ‘we want to address the complex issues of heterogeneity as opposed to the cultural homogenisation of students and help us all grow.’ ((Jones, McCullagh, Watson, 2006).
Issues explored:
• ‘translating’ cultural learning styles with students from a non-Western education background
• integrating/assimilating/enriching the learning mix of domestic and overseas students
• helping students re-draw their own ‘identity map’ from an intra cultural perspective, using the dynamics of mix-culture groups.
• liberating students through cross-cultural learning
• enabling students to become ‘future ready’ in their own understanding of sustainable issues
• dealing with the attendant language and comprehension problems in mixed cultural groups
We are also keen to raise the professional aspects of teaching. To review the history of the art schools in the UK and in one sense, to try and recapture the communal goal, which aimed to improve the manufacturing base, the cultural tastes of a nation, but crucially to re-address this in International terms. (Ewart in Jones, 1996)
Return on Investment in Public Relations: A critical assessment of concepts used by practitioners from the perspectives of communication and management sciences
No full textReturn on Investment (ROI) is a term commonly and non-specifically used by public relations practitioners when discussing the value to be created from communication activities. It mimics business language, particularly from business administration and financial management, but does not figure widely in academic discourse (Watson, 2005).
Although the Institute for Public Relations [now CIPR] undertook a review of ROI practice in the United Kingdom (IPR/CDF 2004) and Likely, Rockland & Weiner (2006) proposed variations of ROI as alternatives to the discredited Advertising Value Equivalence (AVEs) measure of value creation, there has been little discussion other than Macnamara (2007) and Gregory and Watson (2008).
This paper gives an overview on the views of ROI in public relations literature and concepts used by agencies and providers of measurement services. It reports on survey research amongst practitioners in several European countries on identifying the economic value of public relations. The findings are compared with the concepts of ROI used in business and accounting literature (Weber and Schäffer, 2006; Drury, 2007).
Applied theory and parameters for the development of measurement and evaluation techniques are proposed. The paper concludes that the use of the term ROI in public relations needs a proper foundation in overriding management theory; otherwise PR theory and practice will discredit themselves
Leading edge erosion detection for a wind turbine blade using far-field aerodynamic noise
No full textIn this paper, the feasibility of using far-field acoustic measurements as a non-contact monitoring technique for wind turbine blade leading edge erosion is assessed. For this purpose, a DU96 W180 airfoil with several eroded leading edge configurations of different severities is experimentally investigated. The eroded leading edges are designed with pits, gouges and coating delamination scaled from a real eroded blade. To assess the feasibility of the technique in quasi-realistic configurations, experiments are carried out under clean and turbulent inflow conditions. Acoustic measurements are performed with a phased microphone array. In the absence of inflow turbulence, because of the low Reynolds number at which the experiments are carried out, the case with minor erosion severity shows similar far-field noise spectra as the clean leading-edge cases, i.e., the presence of tonal peaks caused by laminar boundary layer instability noise through a self-sustained feedback loop but with higher tonal amplitudes. Increasing the damage level (considered as moderate erosion), the spectra of the noise scattered from the suction side show that the tonal peaks shift to higher frequencies and have lower amplitudes, thus suggesting that the damage alters the flow features responsible for the acoustic feedback loop; whereas, the spectra from the pressure side show a broadband noise distribution. For heavy erosion, the far-field noise spectra show broadband features from both airfoil sides, thus suggesting that the damage has fully forced the transition to turbulent flow; in which case, an increase in the low-frequency content is observed. Conversely, in the presence of turbulent inflow, when comparing the noise scattered at the trailing edge, no difference is found. However, leading edge impingement noise decreases at medium–high frequency compared with the baseline case at a chord-length-based Strouhal number St_C~10. The experimental results also suggest that the delamination feature is the one which is the most easily detectable and the approach is valid for a wide range of angles of attack and inflow velocity
An aeroacoustics-based approach for wind turbine blade damage detection
No full textIn this work, aimed at the development of an aeroacoustics-based wind turbine blade damage detection approach, the noise scattered from two airfoils with damage at the trailing edge or at the leading edge is investigated. Four trailing edge cracks (with width of 0.2, 0.5, 1.0 and 2.0 mm) and four leading edge erosion configurations (consisting of gouges and delamination) are investigated for a NACA 0018 and a DU96 W180 airfoil. Experiments are carried out under clean and turbulent inflow conditions. Acoustic measurements are performed in an anechoic wind tunnel with a microphone array. The trailing edge crack causes a tonal peak at trailing-edge-thickness-based Strouhal number approximately equal to St_h~0.1 under clean and low turbulence intensity inflow conditions (e.g. ~4% in this study). For a higher turbulence intensity (e.g., ~7%), the tonal peaks are not detectable. For the leading edge erosion case, under clean inflow conditions and minor damage levels, the amplitudes of the harmonics in the trailing edge noise spectra increase compared with the baseline. For moderate damage levels, the harmonics on the suction side shift to higher frequencies with lower amplitudes. For the highest damage levels, only broadband characteristics are present, where low-frequency contributions increase and high-frequency contributions decrease as the damage level increases. When introducing turbulent inflow, the leading edge impingement noise level decreases at medium-high frequency (above 1000 Hz) with increasing levels of erosion.Wind Energ
Land lease statement from Watson Land Company to F. [Fusaichi] Takeuchi, May 1, 1938
No full textMonthly statement for one-half year's rent, May 1, 1938 to October 31, 1938 with a sum of $93.7
An initial investigation on the use of ‘Return on Investment” in public relations practice
No full text‘Return on Investment’ (ROI) is usually defined in management literature as a measure of financial effectiveness that is concerned with the returns on capital employed in business (profit-making) activities. In public relations practitioner parlance, however, ROI appears to be used in a much looser form to indicate the results of activity. This mixed method research using an online survey instrument investigated practitioner understanding of the term, primarily in the UK. These findings resulted: 1) Two-thirds of PR practitioners use the term ROI when planning and evaluating communication activity; 2) ROIs related to communication objectives (66.7%) are more widely used than financial-related ROIs (12.8%); 3) There is a clear difference in ROI practices between consultants/freelances and in-house colleagues. Nearly three-quarters of consultants and freelances (73.1%) offer an ROI formula to clients but only 26.3% of in-house practitioners have one; and 4) On the oft-discussed question of an industry-wide ROI formula, only 35.6% supported the proposition with 64.4% opposed. However, the survey also found that practitioner concepts of ROI are very narrowly expressed, mainly in relation to media outputs
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