A Comparative Study of Turbulence Model Effects in Numerical Analyzing Flow around the Buildings Having Various Aspect Ratios / Farklı En-Boy Oranlarına Sahip Binaların Etrafındaki Akışın Sayısal Çözümünde Türbülans Modellerinin Etkisinin Karşılaştırmalı Araştırılması

Energy demand is increasing with the rising world population. Energy consumption for heating purposes are very high in our country so energy saving is very important especially in buildings. The outer walls of the buildings which are designed to have a minimal heat loss will reduce fuel consumption and so it will provide economic benefits. In this study, two dimensional numerical analysing of the buildings having a various aspect ratio (AR) were performed for different wind velocities by using different turbulence models. The standard k-e model, RNG k-e model and realizable k-e model were used for modelling the turbulent flow. For these different geometrical situations, velocity vectors on buildings, heat transfer rate from buildings and turbulence models effects on the solution were investigated in detail. It was observed that with the decreasing wind speeds and aspect ratio, the average heat flux of all surfaces of the building increased depending on the convection coefficient. For the all three models used in the study it was seen that the average heat flux on all of the building surfaces increased depending on the heat transfer coefficient. With the decreasing wind velocities and the building aspect ratio. On the condition of AR=1:1, the three models gave very similar results. The results obtained showed differences with the decreasing in the building aspect ratio. The difference between the results was very little in low velocities, but this difference became clear with the increase in the average wind velocity. Depending on AR and the surface of the building, the heat flux-velocity curves gave similar results in all three models. Hizla artan dunya nufusu ile birlikte enerji kaynaklarina duyulan ihtiyac giderek artmaktadir. Ulkemizde isinma amacli enerji tuketimi oldukca fazladir. Bu manada ozellikle binalarda isi tasarrufu oldukca onemlidir. Bina dis duvarlari uzerindeki akis ve isi transferinin modellenerek en az isi kaybi olacak sekilde tasarlanmasi yakit tuketimini dusurerek ekonomik kazanc saglama konusunda son derece etkilidir. Bu calismada farki en-boy oranlarina (EBO) sahip uc bina ele alinarak, bu binalarin etrafindaki akis farkli ruzgâr hizlari icin uc boyutlu olarak modellenmistir. Turbulans modeli olarak standart k-e model, RNG k-e model ve realizable k-e model ayri ayri kullanilmistir. Bu farkli durumlar icin elde edilen binalar uzerindeki hiz vektorleri, binalardan meydana gelen isi transfer miktarlari ve kullanilan turbulans modellerinin cozum uzerindeki etkileri incelenerek degerlendirmeler yapilmistir. Calismada kullanilan uc modelde de ruzgâr hizlari arttikca ve bina en-boy oranlari azaldikca, tasinim katsayisinin artisina bagli olarak binanin tum yuzeylerindeki ortalama isi akisinin arttigi gorulmustur. Genel olarak, EBO’nun 1:1 olmasi durumunda uc model de yakin sonuclar elde edilmistir. Bina en-boy oraninin azalmasiyla elde edilen sonuclar farkliliklar gostermistir. Sonuclar arasindaki fark dusuk hizlarda yok denilecek kadar az iken ortalama ruzgâr hizinin artmasi ile bu fark belirginlesmistir.  EBO’ya ve binanin yuzeyine bagli olarak isi akisi-hiz degisim egrileri uc modelde de benzerlik gostermistir.