Turbulence model predictions of strongly curved flow in a U-duct

The ability of three types of turbulence models to accurately predict the e ffects of curvature on the flow in a U-duct is studied. An explicit algebra ic stress model performs slightly better than one- or two-equation linear e ddy viscosity models, although it is necessary to fully account for the var iation of the production-to-dissipation-rate ratio in the algebraic stress model formulation. In their original formulations, none of these turbulence models fully captures the suppressed turbulence near the convex wall, wher eas a full Reynolds stress model does. Some of the underlying assumptions u sed in the development of algebraic stress models an! investigated and comp ared with the computed flowfield from the full Reynolds stress model. Throu gh this analysis, the assumption of Reynolds stress anisotropy equilibrium used in the algebraic stress model formulation is Found to he incorrect in regions of strong curvature. By the accounting for the local variation of t he principal axes of the strain rate tensor, the explicit algebraic stress model correctly predicts the suppressed turbulence in the outer part of the boundary layer near the convex wall.