Developing Turbulent Flow in Pipes and Analysis of Entrance Region

Yıl 2021, Cilt: 9 Sayı: 2, 332 - 353, 28.05.2021

Eyüb Canlı Ali Ates Şefik Bilir

https://doi.org/10.21541/apjes.818717

Cited By: 4

Öz

Turbulent flows have complex structures due to its nature and its’ analyses are hard either by numerical or experimental means. Hydrodynamic development of turbulent flow is also complex. In this study, velocity distribution in hydrodynamic entrance length of pipes is investigated depending on axial and radial locations. Literature was surveyed for a single empirical expression that provides velocity profile directly according to Reynolds number, radial and axial locations. Requisite for computational fluid dynamics in hydrodynamic entry length of pipes is stressed by assessing turbulence magnitudes in radial and axial directions. Evaluation of the region and its properties are conducted from heat transfer perspective. An axisymmetric pipe entrance region was analyzed by means of a commercial CFD code with nondimensional parameters. Four different Reynolds numbers that are 5x103, 1x104, 5x104, 1x105 were used in calculations. k-ϵ turbulence model and standard wall functions were used for turbulence modeling. Hydrodynamic entry length, velocity profiles and turbulence indicator parameters results are presented by means of axial and radial profiles. According to the obtained results, radial velocity component values exist that would lead to radial thermal convection in hydrodynamic entrance length. It is found that simultaneous development of velocity profiles and turbulence quantities leads to characteristic velocity profiles. Also, it is seen that a good resolution in hydrodynamic entrance length can be easily achieved by computational fluid dynamics.

Anahtar Kelimeler

Axisymmetric flow, CFD, Hydrodynamic entrance length, k-ϵ turbulence model

Destekleyen Kurum

Yok

Proje Numarası

Yok

Teşekkür

This content is part of PhD dissertation of Eyub CANLI, Selcuk University, Konya, TURKEY

Borularda Gelişen Türbülanslı Akış ve Giriş Bölgesi Analizi

Öz

Türbülanslı akışlar tabiatı gereği karmaşık bir yapıya sahiptirler ve gerek sayısal olarak gerekse deneysel olarak incelenmeleri zordur. Türbülanslı akışın hidrodinamik gelişmesi de oldukça karmaşıktır. Bu çalışmada eksenel ve radyal konumlara bağlı olarak boruların hidrodinamik giriş mesafesinde hız dağılımları incelenmiştir. Reynolds sayısına, eksenel ve radyal konumlara göre doğrudan hız profilini verecek bir deneysel bağlantı için literatür taranmıştır. Ayrıca radyal ve eksenel doğrultuda türbülans büyüklükleri değerlendirilerek boruların hidrodinamik giriş mesafesinde hesaplamalı akışkanlar dinamiğinin gerekliliğini vurgulanmıştır. Söz konusu bölgenin ve özelliklerinin ısı transferi açısından değerlendirilmesi yapılmıştır. Ticari HAD yazılımı ile eksenel simetrik boru giriş bölgesi boyutsuz parametrelerle incelenmiştir. Hesaplamalarda 4 farklı Reynolds sayısı kullanılmış olup bunlar 1x104, 1x105, 5x103 ve 5x104 dür. Türbülans modellemesi için standart k-ϵ türbülans modeli ve standart duvar fonksiyonları kullanılmıştır. Eksenel ve radyal profiller yardımıyla hidrodinamik giriş mesafesi, hız profilleri ve türbülans gösterge parametreleri sonuçları sunulmuştur. Elde edilen sonuçlara göre hidrodinamik giriş mesafesinde radyal doğrultuda ısıl taşınıma yol açacak radyal hız bileşeni değerleri bulunmaktadır. Hız profilleri ile türbülans büyüklüklerinin eş zamanlı gelişiminin karakteristik hız profillerine yol açtığı bulunmuştur. Ayrıca hidrodinamik giriş mesafesinde iyi bir çözünürlüğün kolayca hesaplamalı akışkanlar dinamiği ile elde edilebildiği görülmüştür.

Anahtar Kelimeler

Eksenel simetrik akış, HAD, Hidrodinamik giriş mesafesi, k-ϵ türbülans modeli

Proje Numarası

Yok

Kaynakça

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