Türbülans Şiddetinin Dairesel Bir Silindir Üzerinde Oluşan Akış Yapısına ve Aerodinamiğine Etkisi

Öz

Bu araştırmada, kritik altı Reynolds sayısının, Re=5×103 olduğu durumda k-ω tabanlı DES türbülans modeli kullanılarak türbülans şiddetinin dairesel bir silindir etrafındaki zamana bağlı akış yapısı üzerindeki etkisi hakkında sayısal bir çalışma yapılmıştır. Sayısal analizlere göre, türbülans şiddeti arttıkça ayrılmış akış bölgesinin uzunluğu azalmaktadır. Silindirin arka bölgesinde oluşan ayrılmış akış bölgesinin uzunluğu, Ls silindirin çapı, D ile boyutsuzlaştırılmış ve bu değer, Ls/D türbülans şiddetinin Tu=%0,8 olduğu durumda Ls/D =1,225 olarak ölçülürken, türbülans şiddetinin Tu=%7 olduğu durumda Ls/D =1,0822 değerine azalmıştır. Ayrıca silindir yüzeyinde mutlak negatif basınç katsayısının maksimum olduğu nokta, türbülans şiddeti arttıkça silindir arka bölgesinde oluşan durma noktasına yaklaşmıştır. Türbülans şiddetinin, Tu=%0,8 olduğunu durumdan Tu=%7 ve %12 olduğu durumlara arttırıldığında, sürükleme katsayısının, CD arttığı gözlemlenmiştir. Buradan türbülans şiddeti seviyesinin dairesel bir silindir etrafında oluşan akış karakteristiği ve aerodinamiği üzerinde etkili olduğu sonucuna varılmıştır.

Anahtar Kelimeler

• Küt cisim
• Kritik altı Reynolds sayısı
• Türbülans şiddeti
• Türbülans modeli
• Kararsız akış

The Turbulence Intensity Effect on the Flow Characteristics and Aerodynamics of a Circular Cylinder

Öz

In this investigation, a numerical study about the turbulence intensity effect on the time-dependent flow structure around a circular cylinder employing k-ω based Detached Eddy Simulation (DES) turbulence model was performed at sub-critical Reynolds number of Re=5×103. According to the numerical analyses, the length of recirculation region reduces as the level of turbulence intensity augments. While the normalized length of recirculation region after the cylinder, Ls/D is measured as 1.225 at turbulence intensity of Tu=0.8%, it reduces to the value of Ls/D =1.0822 at turbulence intensity of Tu=7%. Furthermore, the location of peak negative pressure coefficient moves in downstream direction by increasing turbulence intensity. The drag coefficient, CD was observed to increase when turbulence intensity increases from Tu=0.8% to 7% and 12%. Thus, it was concluded that the level of turbulence intensity is effective on changing the flow characteristics and aerodynamics of a circular cylinder.

Anahtar Kelimeler

• Bluff body
• Subcritical Reynolds number
• Turbulence intensity
• Turbulence model
• Unsteady flow

Kaynakça

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