Two-equation versus Reynolds-stress modeling in predicting flow and heat transfer in a smooth U-duct with and without rotation

Computations were performed by using Version 5.5 of the Fluent-UNS code to compare two turbulence models in predicting the three-dimensional flow and heat transfer in a smooth duct of square cross section with a small radius of curvature 180-degree bend under rotating and non-rotating conditions (Re = 25,000; Ro = 0.0 and 0.24). The two turbulence models investigated are the standard k-ε model and a Reynolds stress model. For both models, the two-layer low-Reynolds model of Chen and Patel was used in the near-wall region. Results obtained show that though the k-ε model predicts turbulence quantities incorrectly, the predicted velocity and temperature fields and the surface heat transfer are similar to those from the Reynolds stress model when there is no rotation. When there is rotation, there is significant difference in the predicted surface heat transfer on the leading surface. But, the predicted flow field is still qualitatively similar.