Experimental and Numerical Analysis of Flow around a Circular Bridge Pier

Öz

The turbulent flow field around a circular pier is complex due to separation and generation of multiple vortices in different structures. This topic has a great interest in engineering applications for the design of the bridges over water. In this study, the velocity field of flow around a circular pier is measured using Laser Doppler Anemometry (LDA). The Basic equations of the problem are solved by ANSYS-Fluent program package based on finite volume method for the flow case having the same experimental conditions. In the numerical simulations, Standard k-ε, Renormalization Group k-ε and Realizable k-ε turbulence closure model are used for the simulation of turbulence, and the flow profile is computed using Volume of Fluid method. Grid Convergence Index (GCI) is performed to examine the effect of the selected grid structure on the numerical results. The computed results for velocities and free surface profiles are compared with measured data. The comparisons of the experimental and numerical results show that Realizable k-ε is more successful turbulence model among the other models in predicting the velocity field and free surface profiles.

Anahtar Kelimeler

• Bridge pier,LDA,RANS,turbulence modeling,VOF

Köprü Ayağı Etrafındaki Türbülanslı Akımın Sayısal ve Deneysel Analizi

Öz

Dairesel bir köprü ayağı etrafındaki türbülanslı akış alanı, çoklu girdapların oluşumu nedeniyle karmaşık bir yapıya sahiptir. Köprü ayağı etrafında meydana gelen bu karmaşık akım yapısının belirlenmesi, bu tür yapıların tasarımı açısından önem kazanmaktadır. Bu çalışmada köprü ayağı etrafındaki üç boyutlu türbülanslı akımın hız alanı laboratuvar ortamında Lazer Doppler Anemometresi (LDA) ile ölçülmüş ve deney ile aynı koşullardaki akım için temel denklemler, sonlu hacimler yöntemine dayalı ANSYS-Fluent paket programı ile sayısal olarak çözülmüştür. Sayısal modellemede, Standard k-ε, Renormalization Group k-ε ve Realizable k-ε türbülans modeli kullanılmış ve serbest su yüzü profili Akışkan Hacimleri Yöntemi ile hesaplanmıştır. Seçilen ağ yapısının sayısal sonuçlara olan etkisini incelemek için Ağ Yakınsama İndeksi (GCI) kullanılmıştır. Sayısal sonuçlardan elde edilen hız alanı ve su yüzü profilleri deneysel ölçümlerle karşılaştırılmış, Realizable k-ε türbülans modelinin köprü ayağı etrafındaki akım alanını belirlemede diğer modellere göre daha başarılı olduğu tespit edilmiştir. 

Anahtar Kelimeler

• Köprü ayağı,LDA,RANS,türbülans modellemesi,VOF

Kaynakça

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