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In this study, anomalous geometries were examined computationally and experimentally in terms of their aerodynamic performance as energy harvesters. The main motivation of this study is that most of these geometries, discussed in the present study, have not been previously considered as energy harvesters in literature. Some well-known geometries alongside these anomalous models were also investigated for comparison in this current study. The examination was conducted by means of the computational and experimental fluid dynamics approaches where the flow around these different models was analyzed in detail to shed light on the crucial aspects encountered during the flow separation over these various geometries. By this means, the lift coefficients of the investigated harvester geometries were considered as the essential parameter for time-dependent analyses in the numerical simulations since this parameter is the main reason for the flow-induced vibrations. Moreover, experimentally obtained voltages and power curves were compared for different geometries. Based on the root mean square values of the numerical lift coefficients, it was found that the best aerodynamically beneficial model is Model-7 (equal-length 3-tines fork shape) and the worst model is Model-5 (perpendicular plane). Velocity vectors and pressure distributions around these best and worst models were also provided to reveal the main differences in flow structures that may lead to a better design of energy harvester geometry for further studies.
In this article, a two-dimensional, incompressible flow around a NACA 63-415 airfoil, which is widely used as one of the commercial wind turbine blade profiles, is investigated. The goal of this research is to obtain the optimum angle of attack for this particular type of airfoil within a precise range. The Reynolds-Averaged Navier-Stokes (RANS) technique of Computational Fluid Dynamics (CFD) has been employed to examine the flow where the Reynolds number is in the range of 10 5 to 3×10 6 and also for the angles of attack from 0° to 20°. These are the typical flow conditions mostly encountered in the real applications of wind turbine blades. The turbulent flow is modelled by means of the Spalart-Allmaras turbulence model since its capability of simulating aerodynamic flows. The ratio of the lift force to the drag force acting on the airfoil has been chosen as a control parameter since the lift force increases the power generated by the turbine, whereas the drag force negatively affects the performance. The present numerical result shows that the maximum lift to drag ratio is observed between 2.5° and 3.5°, depending on the Reynolds number. Onur ERKAN https://orcid.org/0000-0001-7488-8039 Musa ÖZKAN https://orcid.org/0000-0002-1322-3276 Cite as: Erkan O, Özkan M. 2020. Investigation of the flow over NACA 63-415 airfoil. BSJ Eng Sci, 3(2): 50-56.
Bu çalışmada, sınır tabaka akışı aktif kontrol yöntemlerinden biri olan, sınır tabakadan kanat içerisine hava emilmesi prensibine dayanan emme tekniği kullanılarak bir rüzgar türbini kanadının aerodinamik performansının arttırılması hedeflenmiştir. Emme işlemi daimi bir jet vasıtasıyla gerçekleştirilmiş, kanat modeli olarak rüzgar türbini uygulamalarında yaygın olarak kullanılan S809 kanat profili tercih edilmiştir. Çalışma parametreleri olarak, üç ayrı jet konumu (Ljet = 0.1c, 0.26c, 0.36c) ve üç ayrı jet oranı (Rjet = 0.1, 0.3, 0.5) seçilmiştir. Emme jeti genişliği sabit olup veter uzunluğunun %2.5'i kadar ve emme jeti açısı (θjet) bölgesel jet yüzeyine 90° olacak şekilde ayarlanmıştır. İki boyutlu türbülanslı akış için sayısal analiz; α = 15° hücum açısında ve Re = 10 6 'da SST k-ω türbülans modeli kullanılarak gerçekleştirilmiştir. İlk olarak emme jeti konumunun etkisi, ardından en iyi sonucu veren emme jeti konumu seçilerek emme jeti oranının etkisi araştırılmıştır. Kanat profili etrafındaki akışa ait simülasyon sonuçları incelendiğinde, en iyi sonuç emme jeti konumu 0.36c (Jet-3) ve emme jeti oranı 0.5 olduğunda alınmıştır. Jet kullanılmadığı duruma göre CL/CD oranı 17.92'den 273.03'e yükselmiştir. Emme jeti ile kontrol yönteminin uygulanması ile kontrolsüz duruma göre Cl değeri yaklaşık olarak 1.211'den 1.8'e yükselmiş, Cd değeri ise 0.068'den 0.0066'ya düşmüştür.
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