Flow Structures Around Tandem Cylinders Near Wall

Yıl 2024, Cilt: 29 Sayı: 2, 601 - 610, 31.08.2024

Engin Pınar , Gökhan Yaşar

https://doi.org/10.53433/yyufbed.1425502

Öz

In this study, a comparative study of the flow structure formed by changing the distance between two consecutively placed circular cross-section cylinders and the base was investigated experimentally using the Particle Imaging Velocimetry Technique (PIV). Experiments were carried out for three different height ratios in the water channel: h/D = 0, 0.5 and 1. The height ratio is defined as the ratio of the cavity height (between the bottom surface of the circular cylinder and the wall surface). The distance between consecutively placed cylinders was defined as the G/D gap ratio, and it was kept constant throughout the experiments as G/D = 1. Depending on the cylinder diameter, D is determined as the Reynolds number, Re = 2100, and the thickness of the boundary layer is δ/D = 0.4. Experimental results were evaluated by taking into account time-averaged streamlines <ψ>, time-averaged vortex contour lines, <ω>, and Reynolds stresses. The findings showed that the void ratio, G/D and height ratio have a significant impact on the flow structures around H/D cylinders. As can be seen from the flow data obtained from the experiment, it has been observed that the separation point on the cylinder and the dead flow zone behind the cylinder vary at different cylinder heights. In addition, it was determined that the vortex sizes, <ω>, and Reynolds shear stress values formed in the dead flow region differ depending on the cylinder height. It has been determined that the flow around a pair of cylinders has a more complex, unstable, and highly variable structure than that of a single cylinder.

Anahtar Kelimeler

Circular cylinder, Flow structure, Near wall, Turbulance, Wake region

Duvara Yakın Tandem Silindirler Etrafındaki Akış Yapıları

Öz

Bu çalışmada, ard arda yerleştirilmiş dairesel kesitli iki silindirin tabanla aralarındaki mesafenin değiştirilmesi ile oluşan akış yapısının karşılaştırmalı bir çalışması Parçacık Görüntülemeli Hız Ölçme Tekniği (PIV) kullanılarak deneysel olarak araştırıldı. Su kanalında h/D = 0. 0.5 ve 1 olmak üzere üç farklı yükseklik oranı için deneyler yapılmıştır. Yükseklik oranı, boşluk yüksekliğinin (dairesel silindirin alt yüzeyi ile duvar yüzeyi arasındaki) silindir çapına oranı olarak tanımlanmaktadır. Ard arda yerleştirilen silindirler arasındaki mesafe G/D boşluk oranı olarak tanımlanmış olup, G/D = 1 olarak deneyler süresince sabit tutulmuştur. Silindir çapına bağlı, D, Reynolds sayısı, Re = 2100 ve sınır tabakasının kalınlığı δ/D = 0.4 olarak belirlenmiştir. Deney sonuçları zaman ortalamalı akım çizgileri <ψ>, zaman ortalamalı girdap eş düzey eğrileri, <ω>, ve Reynolds gerilmeleri, dikkate alınarak değerlendirilmiştir. Bulgular, yükseklik oranın, h/D silindirler etrafındaki akış yapıları üzerinde önemli bir etkiye sahip olduğunu göstermiştir. Deneyden elde edilen akış verilerinden de anlaşılacağı üzere, silindir üzerindeki ayrılma noktasının ve silindir arkasındaki ard izi bölgesinin farklı silindir yüksekliklerinde değişim gösterdiği gözlemlenmiştir. Bunun yanı sıra, ölü akış bölgesinde oluşan vorteks büyüklüklerinin ve Reynolds kayma gerilmesi değerlerinin de silindir yüksekliğine bağlı olarak farklılıklar gösterdiği belirlenmiştir. Silindir çiftinin etrafındaki akışın tek silindire göre daha karmaşık, kararsız ve çok değişken bir yapıya sahip olduğu belirlenmiştir.

Anahtar Kelimeler

Akış yapısı, Ard izi, Dairesel silindir, Türbülans, Yakın duvar

Etik Beyan

YOK

Destekleyen Kurum

Koluman Otomotiv Endüstri A.Ş, 33450, Mersin/Türkiye

Teşekkür

Koluman Otomotiv Endüstri A.Ş, 33450, Mersin/Türkiye

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