Application of non-linear kappa-omega model to a turbulent flow inside a sharp U-bend

Simulation of the complex flow inside a sharp U-bend needs both refined tur bulence models and higher order numerical discretization schemes. In the pr esent study, a non-linear low-Reynolds number (low-Re) k-omega model includ ing the cubic terms was employed to predict the turbulent flow through a sq uare cross-sectioned U-bend with a sharp curvature, R-C/D = 0.65. In the tu rbulence model employed for the present study, the cubic terms are incorpor ated to represent the effect of extra strain-rates such as streamline curva ture and three-dimensionality on both turbulence normal and shear stresses. In order to accurately predict such complex flowfields, a higher-order bou nded interpolation scheme (Song et al., 1999) has been used to discretize a ll the transport equations. The calculated results by using both the non-li near k-omega model and the linear low-Reynolds number k-epsilon model (Laun der and Sharma, 1974) have been compared with experimental data. It is show n that the present model produces satisfactory predictions of the flow deve lopment inside the sharp U-bend and well captures the characteristics of th e turbulence anisotropy within the duct core region and wall sub-layer.