The computation of flow and heat transfer through an orthogonally rotating square-ended U-bend, using low-Reynolds-number models

In this contribution we present computations of heat and fluid flow through a square-ended U-bend that rotates about an axis normal to both the main flow direction and also the axis of curvature. Zonal and low-Reynolds-number models are used at effective viscosity (EVM) level and also at second-moment-closure (DSM) level. Moreover, two length-scale correction terms are used with the low-Re models, the original Yap term and a differential form that does not require the wall distance (NYap). The resulting predictions are compared with available flow measurements at a Reynolds number of 100,000 and a rotation number (OmegaD/U-B) of 0.2 and also with heat transfer measurements at a Reynolds number of 36,000 rotation number of 0.2 and Prandtl number of 5.9 (water). The main flow features are well reproduced by all models. The mean flow development within and just after the bend is better reproduced by low-Re models. Turbulence levels within the rotating U-bend are under-predicted, but DSM models produce a more realistic distribution. Along the leading side all models over-predict heat transfer levels just after the bend. Along the trailing side, the heat transfer predictions of the low-Re DSM with the NYap are close to the measurements. The introduction of a differential form of the length-scale correction term tends to improve the heat transfer predictions of both low-Re models.