Sciences & technologie. B, Sciences de l’ingénieur
Volume 0, Numéro 37, Pages 14-30
2013-06-30
Contribution To The Dynamics Of The Three-dimensional Flows In Square-sectioned Curved Ducts
Authors : Gaci Farid . Nemouchi Zoubir . Khezzar Lyes .
Abstract
A numerical study of laminar and turbulent fluid flows in 90° and 180° bends of square section was carried out. Threedimensional meshes, based on hexahedral cells, were generated. The QUICK scheme was employed to discretize the convective term in the transport equations. The SIMPLE algorithm was adopted to treat the velocity-pressure coupling. The flow structure obtained showed interesting features such as recirculation zones and counter-rotating pairs of vortices. The performance of three different turbulence models was evaluated: the standard k- model, the SST k-ω model and the Reynolds Stress Model (RSM). Overall, it was found that, the multi-equation model performed better than the two equation models. In fact, the existence of four pairs of counter rotating cells, in the straight duct upstream of the bend, were predicted by the RSM closure but not by the standard eddy viscosity model nor the SST k-ω model. Furthermore, the recirculation zone along the inner wall in the second part of the U-bend is better captured by the RSM. The analysis of the results led to a better understanding of the induced three dimensional secondary flows and the behaviour of the local pressure coefficient and the friction coefficient.
Keywords
Curved duct, counter-rotating cells, secondary flow, laminar, turbulent.
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