Experimental Investigation of the Flow Characteristics around a NACA0012 Airfoil Subjected to Stall and Post-Stall Conditions

Öz

The flow structure and turbulent characteristics of an airfoil at various Reynolds numbers (Rec = 1.5×104, 2.0×104, 2.5×104) have been investigated considering two angles of attack (α = 10o and α = 12o). PIV measurements have been performed and time-averaged and instantaneous results were presented utilizing vorticity, profiles of streamwise velocity, Reynolds shear stress, and turbulent kinetic energy distributions. The results have shown that both the Rec and α significantly affect the flow characteristics around the airfoil. Furthermore, the change in flow characteristics between the stall and post-stall angles was elaborated and compared with each other, as being in good agreement with the available literature. The turbulent fluctuations in the airfoil wake, as well as in the suction side, were obtained to be more intense at post-stall angle compared with the stall condition. Besides, due to the earlier flow separation, post-stall condition presented a larger wake and the shedding of vortices formed by the leading and trailing edges of the airfoil.

Anahtar Kelimeler

• Airfoil
• Stall
• PIV
• Flow structure

Stol ve Stol Ötesi Durumlara Maruz Kalan Bir NACA0012 Kanat Profili Etrafındaki Akış Karakteristiklerinin Deneysel İncelenmesi

Öz

Bir kanat profilinin akış yapısı ve türbülans özellikleri, çeşitli Reynolds sayılarındaki (Rec =1,5×104, 2,0×104, 2,5×104) iki atak açısı (α=10o ve α=12o) göz önüne alınarak incelenmiştir. PIV ölçümleri gerçekleştirilmiş ve zaman ortalamalı ve anlık girdap, akış hızı profilleri, Reynolds kayma gerilmesi ve türbülans kinetik enerji dağılımları kullanılarak sonuçlar sunulmuştur. Sonuçlar, hem Reynolds sayısının hem de hücum açısının, kanat profili etrafındaki özelliklerini önemli ölçüde etkilediğini göstermiştir. Stol ve stol ötesi açılarda akış karakteristiklerindeki değişiklik, mevcut literatürle iyi bir uyum içinde detaylandırılmış ve birbirleriyle karşılaştırılmıştır. Hem kanat profili art izinde hem de emme yüzeyinde oluşan türbülans çalkantılarının, stol ötesi açıda daha şiddetli olduğu elde edilmiştir. Bunun yanında, daha erken akış ayrılması sebebiyle stol ötesi durum, kanat profilinin hücum ve firar kenarlarından doğan girdapların kopması ile birlikte daha geniş bir art izi yapısı göstermiştir.

Anahtar Kelimeler

• Kanat profili
• Stol
• PIV
• Akış yapısı

Kaynakça

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