DUVAR YAKININDA ART ARADA YERLEŞTİRİLMİŞ KARE KESİTLİ SİLİNDİRLER ETRAFINDA AKIŞ VE ZORLANMIŞ TAŞINIM İLE ISI GEÇİŞİ

Bu çalışmada bir duvar yakınında arka arkaya yerleştirilmiş ısıtılmış kare kesitli silindirler etrafındaki akışın karakteristiklerini ve ısı geçişi incelenmiştir. Hesaplamalar zamana bağlı 2-boyutlu Navier Stokes ve enerji denklemlerinin çözümü ile gerçekleştirilmiştir. Denklemlerin viskoz ve taşınım terimleri için Cranck-Nicholson şeması ile birlikte kısmi adımlar metodu kullanılmıştır. Girişte duvara paralel hız bileşeni için tam gelişmiş laminar sınır tabaka kullanılmış, akışa dik yönünde hız bileşeni sıfır olarak alınmıştır. Simulasyonlar 0.71 Prandtl (Pr) sayısı ve akışın iki boyutlu olduğu Reynolds (Re) sayısının 150 değeri için gerçekleştirilmiştir. Akış karakteristikleri ve ısı geçişi yalnızca silindirler arasındaki uzaklık (L/D) ye değil aynı zamanda silindirlerin merkezi ile duvar arasındaki uzaklığa da (G/D) bağlıdır. Akış ve ısı geçişi arasındaki bağlantıyı ortaya çıkarmak için değişik L/D ve G/D oranları için çevrinti ve eş sıcaklık eğrileri elde edilmiş ve tartışılmıştır. Silindirler duvardan oluşan sınır tabakanın içerisinde kaldığında, silindirlerin üst ve alt yüzeyindeki hızlar arasındaki büyük fark akış ve ısı geçiş parametrelerinde önemli değişimlere neden olmuştur.

Anahtar Kelimeler:

Isı geçiş, sayısal simulasyon, art arda kare kesitli silindirler, duvar etkisi

FLOW AND FORCED HEAT TRANSFER FROM TANDEM SQUARE CYLINDERS NEAR A WALL

In this study, the flow and heat transfer characteristics of two heated square cylinders in a tandem arrangement near a wall is investigated. The numerical computations are carried out by solving the unsteady two dimensional Navier-Stokes and energy equations. A fractional step method with Crank-Nicholson schema was employed to the convective and the viscous terms of the equations. At the inlet, fully developed laminar boundary layer is employed for longitudinal velocity over the plane wall while transverse velocity set to zero. The simulations are performed for Prandtl number (Pr) of 0.71 and Reynolds number (Re) of 150 where the flow is considered two dimensional. The flow field characteristics and heat transfer depend not only on the ratio of the space between the cylinders (L/D) but also on the distance between the cylinder center and the wall (G/D). The vorticity and isotherm curves are generated and discussed for various L/D and G/D ratios to clarify the connection with flow and heat transfer characteristics. When the cylinders are within the boundary layer formed on the plane wall, the large difference between the velocities at the upper and lower side of the cylinders leads to noticeable variation at the flow and heat transfer characteristics.

Keywords:

Heat Transfer, Numerical Simulation, Tandem square cylinders, Wall effect,

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