Computation of wall heat transfer in pipe-expansion flows with/without swirl

Computation of wall heat transfer in pipe-expansion flows with/without swirl motion is implemented using a new tow-layer (hybrid) turbulence model which is composed of a Reynolds stress model (RSM) and a Low-Reynolds-number (LRN) k - ε model. Comparisons of the predicted distributions of the Nusselt number along the wall with the available experimental results reveal that this two-layer turbulence model yields satisfactory performances in the three test cases. It is also shown that appreciable superiority of this two-layer turbulence model over a pure LRN k - ε model is observed when the investigated flow becomes more complex (anisotropic) such as the recirculating swirling flow case.