Prediction of developing turbulent ow in 90◦-curved ducts using linear and non-linear low-Re k– models

This paper reports the outcome of applying two di erent low-Reynolds-number eddy-viscosity models to resolve the complex three-dimensional motion that arises in turbulent ows in ducts with 90◦ bends. For the modelling of turbulence, the Launder and Sharma low-Re k– model and a recently produced variant of the cubic non-linear low-Re k– model have been employed. In this paper, developing turbulent ow through two di erent 90◦ bends is examined: a square bend, and a rectangular bend with an aspect ratio of 6. The numerical results indicate that for the bend of square cross-section the curvature induces a strong secondary ow, while for the rectangular cross-section the secondary motion is con ned to the corner regions. For both curved ducts, the secondary motion persists downstream of the bend and eventually slowly disappears. For the bend of square cross-section, comparisons indicate that both turbulence models can produce reasonable predictions. For the bend of rectangular cross-section, for which a wider range of data is available, while both turbulence models produce satisfactory predictions of the mean ow eld, the non-linear k– model returns superior predictions of the turbulence eld and also of the pressure and friction coe cients. Copyright ? 2006 John Wiley & Sons, Ltd.