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

Abstract

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. Two-layer and low-Reynolds-number mathematical models of turbulence are used at effective-viscosity (EVM) level and also at second-moment-closure (DSM) level. Moreover, two length-scale correction terms to the dissipation rate of turbulence 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 and heat transfer measurements of water. While the main flow features are well reproduced by all models, the development of the mean flow within and just after the bend is better reproduced by the low-Re models. Turbulence levels within the rotating U-bend are underpredicted, but DSM models produce a more realistic distribution. Along the leading side, all models overpredict 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.

Internal blade cooling: The Cinderella of computational and experimental fluid dynamics research in gas turbines

“…The impact of such steep variations on thermal stresses within the blade certainly merits examination. Industrial designers still tend to work with side-averaged Nusselt numbers and one of the Kelemenis data sets is compared in those terms with computations by Nikas and Iacovides [55] in Fig. 13.…”

“…Fig.13Side-averaged Nusselt number for a rotating U-bend; Experiment: Iacovides et al[52];Computations: Nikas and Iacovides[55], Re ¼ 36 000, Ro ¼ 0.2, s ¼ 5.9 (water)…”