A STRATEGY FOR CREATING PRISMATIC MESH LAYERS FOR MODELLING FLOW OF THE AHMED BODY USED IN VEHICLE AERODYNAMICS

Year 2022, Volume: 10 Issue: 3, 776 - 785, 30.09.2022

Sinan Keiyinci , Mustafa Atakan Akar , Oğuz Baş , Mustafa Özcanlı

https://doi.org/10.21923/jesd.980458

Abstract

In this paper, a mesh generation strategy was investigated on a CFD simulation for Ahmed body which is commonly used in automotive aerodynamics. Generally, in these studies, different kinds of methods can be seen for creating prismatic mesh layers to solve turbulent boundary layers. An insufficient prismatic mesh layer is missing in solving the boundary layer, while the excess of this layer also increases the number of meshes, hence the solution time. In this study, the flow structure of the Ahmed body was studied by using the ANSYS-Fluent™ software at the Reynolds number of Re=2.83×106 depending on the flow rate (u∞=40 m/s) and the body length. The Prismatic mesh layer was generated using mathematical expressions and the results of this mesh were examined both quantitively and qualitatively and further results were evaluated again with a final mesh with a different strategy. To conclude, better results were obtained with developed meshes for modeling the flow profile on the turbulent boundary layer compared to the roughly generated initial mesh. In addition, closer results to the experimental value of CD and CL were obtained at developed meshes compared to the mesh that was roughly applied.

Keywords

CFD, Ahmed Body, Vehicle Aerodynamics, Boundary Layer, Mesh.

TAŞIT AERODİNAMİĞİNDE KULLANILAN AHMED CİSMİNİN AKIŞ MODELİ İÇİN PRİZMATİK AĞ KATMANI OLUŞTURURKEN İZLENECEK STRATEJİ

Abstract

Bu makalede, otomotiv aerodinamiği literatüründe sıklıkla kullanılan Ahmed cismi için bir HAD benzetiminde ağ oluşturma stratejisi üzerine bir çalışma yapılmıştır. Genel olarak bu çalışmalarda, türbülanslı sınır tabaka bölgelerini modellemek için prizmatik ağ katmanı oluştururken farklı yöntemler gözlemlenmektedir. Yetersiz bir prizmatik ağ katmanı sınır tabakasını çözmede eksik kalırken, bu katmanın gereğinden fazla olması ise ağ sayısını, dolayısıyla çözüm sürelerini artırmaktadır. Bu çalışmada, Ahmed cisminin akış yapısı, Ansys-Fluent™ programı ile akış hızına (U∞=40 m/s) ve gövde uzunluğuna bağlı Reynolds sayısı Re=2.83×106 olacak şekilde incelenmiştir. Matematiksel ifadelerden yararlanılarak oluşturulan prizmatik ağ katmanı ve bu ağın sonuçları hem nitel hem de nicel yönden incelenip, farklı bir strateji geliştirilen son bir ağ ile sonuçlar tekrar değerlendirilmiştir. Sonuç olarak, kabaca oluşturulan ilk ağ ile sonradan geliştirilen ağlar arasında, sınır tabakası üzerindeki akış profilini modellemede daha iyi bulgular elde edilmiştir. Ayrıca CD ve CL için deneysel yöntemle elde edilen sonuçlara, geliştirilen ağlarda, kabaca uygulanan ağa göre daha yakın sonuçlar elde edilmiştir.

Keywords

HAD, Ahmed Cismi, Taşıt Aerodinamiği, Sınır Tabakası, Çözüm Ağı

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