Türbülans Yoğunluğunun Geçiş Yer Tahminine Etkisinin Bölgesel Korelasyon Geçiş Modeli ile İncelenmesi

Öz

Aerodinamik katsayılar hava/deniz araçlarının uçuş performans analizlerinde kullanılan en önemli katsayılardır. Serbest akış türbülans yoğunluğu, sayısal akışkanlar dinamiği analizleri ve rüzgar tüneli testleri ile elde edilen aerodinamik katsayılar üzerinde kayda değer etkiye sahiptir. Bu çalışmada, serbest akış türbülans yoğunluğunun küremsi geometri üzerindeki türbülans geçiş yerine etkisi en yaygın kullanılan bölgesel korelasyon geçiş modeli ile analiz edilerek incelenmiştir. Analizler 6.5 x 106 Reynolds sayısında, 0 ve 5 derece farklı hücum açısında gerçekleştirilmiştir. 5 derece hücum açısında yapılan analiz sonuçları hali hazırda mevcut deneysel çalışma ile karşılaştırılmıştır. Serbest akış yoğunluğunun etkisi, eksenel ve normal kuvvet katsayıları ile yüzey sürtünme katsayı dağılımı üzerinden değerlendirilmiştir. Eksenel ve normal kuvvet katsayıları incelendiğinde serbest akış türbülans yoğunluğunun artmasıyla katsayıların arttığı gözlemlenmiştir. Çalışmada ele alınan türbülans yoğunluğu aralığı içerisinde, katsayılarda oluşan farkların uçuş performans analizlerinde kayda değer fark yaratabileceği değerlendirilmiştir. Yüzey sürtünme katsayıları değerlendirildiğinde, geçiş modeli serbest akış türbülans yoğunluğunun artmasıyla geçiş yerini beklenildiği gibi daha önde tahmin etmiştir. Fakat modelin geometri üzerindeki geçiş bölgesi geometrisini deneysel sonuçlara göre oldukça farklı bulduğu görülmüştür.

Anahtar Kelimeler

• Türbülans yoğunluğu
• türbülans geçiş modeli
• 6:1 küremsi geometri
• türbülans geçiş yer tahmini

Effect of Turbulence Intensity on Transition Location Estimation Using Local Correlation Transition Model

Abstract

Aerodynamic parameters are among the most important parameters in flight performance analyses of air/sea vehicles. Free stream turbulence intensity has significant importance on aerodynamic parameters obtained with computational fluid dynamic analyses and wind tunnel tests measurements. In this study, the effect of free stream turbulence intensity on the transition locations of spheroid geometry using with the widely accepted local correlation transition model. The computations are performed at 6.5 x 106 Reynolds number with 0 and 5 degree angle of attacks. The computations at 5 degree angle of attack are compared with an available experimental study. The effect of free stream turbulence intensity is investigated with axial force coefficient, normal force coefficient, and surface friction coefficient distributions. It is seen that axial and normal force coefficients increase with increasing free stream turbulence intensity. The differences in force coefficients obtained with the free stream intensity range used in the study shall create noteworthy effects in flight performance analyses. When surface friction coefficients are investigated, the transition model estimates the transition locations earlier while free stream turbulence intensity increases as expected. However, the transition front geometry is obtained significantly different with respect to the experimental results.

Keywords

• Turbulence intensity
• transition model
• 6:1 spheroid geometry
• ttransition location estimation

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