Ard Arda Dizilimdeki Sonlu Dairesel Silindirlerden Üç Boyutlu Akış ve Isı Transferinin Sayısal İncelenmesi

Abstract

Bu çalışmada, eş uzunluktaki sonlu dairesel silindirlerin üç boyutlu akış ve ısı transferi karakteristikleri sayısal olarak incelenmiştir. Çapı D ve boy/en oranı (AR=3) olan iki sonlu silindir, zemin düzlemine dik olarak yerleştirilmiş ve Re = 20.000 değerine karşılık gelen düzgün bir dış akışa maruz bırakılmıştır. Silindirler arası merkezden merkeze mesafe S/D = 1, 2 ve 4 olacak şekilde değiştirilmiştir. Denklemler, SST k–ω türbülans modeli kullanılarak çözülmüştür. İlk olarak, literatürde mevcut deneysel verilerle karşılaştırma yapılarak en uygun türbülans modeli ve ağ yapısı belirlemek amacıyla tek bir sonlu silindir için doğrulama çalışması gerçekleştirilmiştir. Ardından, ard arda dizilimdeki iki silindir için akış ve ısı transferi davranışları analiz edilmiştir. Akış alanındaki temel türbülans yapıları, akış karakteristikleri ve yüzey basınç dağılımları tablo ve grafikler halinde sunulmuştur. Isıl performans, her bir silindir üzerindeki yerel ve ortalama Nusselt sayısı dağılımları üzerinden değerlendirilmiştir. Sonuçlar, S/D = 1 durumunda düzensiz girdap ayrılmaları nedeniyle Kármán girdap caddesinin oluşmadığını, buna karşın S/D = 4 durumunda kararlı ve periyodik bir uyanım yapısının geliştiğini göstermiştir. Isı transferi açısından, en yüksek ısı transfer performansı yukarı akıştaki silindir için S/D = 1 durumunda, aşağı akıştaki silindir için ise S/D = 4 durumunda elde edilmiştir.

Keywords

• Dış akış
• Türbülanslı akış
• Hesaplamalı akışkan akışı
• Isı transferi
• Sonlu ard arda silindirler.

Numerical Investigation of Three-Dimensional Fluid Flow and Heat Transfer from Finite Circular Cylinders in Tandem Arrangement

Abstract

In this study, three-dimensional flow and heat transfer characteristics from finite circular cylinders of equal length are numerically investigated. Two finite circular cylinders of diameter D and aspect ratio AR=3 placed vertically on the computation domain's bottom wall (ground plane) are subjected to uniform external flow such that Re=20000 is attained. The distance between the cylinders S was varied as S=D, 2D, 4D. The turbulence model SST k- was used to solve the governing equations. Initially, a numerical verification study was carried out to determine the most suitable turbulence model and grid configuration using a single 3D cylinder for which data were available in the literature. Subsequently, the flow fields were obtained for two 3D cylinders arranged in a tandem. The main turbulence and flow characteristics appearing along the flow domain and on each cylinder surface were identified and presented in tabular form. The heat transfer effects of the flow over isothermal cylinders were evaluated using the mean and local Nusselt distributions, leading to recommendations for design improvements. While Kármán Street does not develop in the case of S/D=1 due to the observed irregular vortex separations, a stable Kármán Street is obtained for S/D=4. In terms of heat transfer, the highest heat transfer performance was observed in the case of S/D=1 for the upstream cylinder and S/D=4 for the downstream cylinder.

Keywords

• External flow
• Turbulent flow
• Computational fluid flow
• Heat transfer

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