Numerical Calculations for the Length of the Transitory Zone in Partially Filled Circular Pipes with Steep Slope

Öz

Three-dimensional turbulent free-surface flow through smooth and corrugated circular pipes with steep slope is simulated by means of Computational Fluid Dynamics (CFD). For this purpose, the three-dimensional Reynolds Averaged Navier-Stokes equations are solved using the ANSYS Fluent solver, while interface between air and water is calculated using the Volume of Fluid (VOF) method. Effect of inlet conditions regarding the Froude and Reynolds numbers, channel slope and filling ratio on the length of flow development is investigated while both sub-critical and super-critical inlet conditions are considered. Results of the numerical calculations show that uniform open channel flow is guaranteed roughly 110 and 60 diameters downstream the pipe inlet, for smooth and corrugated pipes, respectively. The transitory length shows a tendency to decrease with the Reynolds number, contrary to the entrance length in pipe flow.

Anahtar Kelimeler

• Uniform open-channel flow
• smooth pipe
• corrugated pipe
• computational fluid dynamics
• volume of fluid method.

Kısmen Dolu Yüksek Eğimli Dairesel Borularda Geçiş Bölgesi Uzunluğunun Sayısal Olarak Hesaplanması

Öz

Yüksek eğimli pürüzsüz ve oluklu dairesel borulardaki üç boyutlu türbülanslı serbest yüzey akışı Hesaplamalı Akışkanlar Dinamiği (HAD) aracılığıyla hesaplanmıştır. Bu amaçla üç boyutlu Reynolds Ortalamalı Navier-Stokes denklemleri ANSYS Fluent yazılımı kullanılarak çözülürken, hava ve su arasındaki arayüzey Volume of Fluid (VOF) yöntemi kullanılarak hesaplanmıştır. Froude ve Reynolds sayıları, kanal eğimi ve doluluk oranına ilişkin giriş koşullarının akış gelişim uzunluğuna etkisi araştırılmış, kritik-altı ve kritik-üstü giriş koşulları göz önünde bulundurulmuştur. Sayısal çözüm sonuçları, dairesel pürüzsüz ve oluklu borular için boru girişinden akım altı yönünde yaklaşık 110 ve 60 çap mesafede üniform açık kanal akışının garanti edilebileceğini göstermektedir.

Anahtar Kelimeler

• Üniform açık kanal akışı
• pürüzsüz boru
• oluklu boru
• hesaplamalı akışkanlar dinamiği
• volume of fluid yöntemi

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