Improved anisotropic turbulence modeling for CFD applications in the IRIS design

An improved realizable anisotropic turbulence model is proposed for application to the analysis of nuclear reactor systems. A cubic stress strain correlation is adopted in order to overcome the typical limitations related to the eddy-viscosity assumption, and an optimized low-Reynolds formulation based on Direct Numerical Simulation (DNS) is included to produce the correct damping of the turbulent viscosity in the near wall region. The model is aimed at including an enhanced physical description, accounting for normal stresses inequality, mean streamline curvature and flow swirling, which often play an essential role in engineering flows, but are not considered in classic eddy-viscosity approaches. The validity of the present formulation is assessed on a series of relevant flows, which allow to confirm the accuracy and especially the greater generality deriving from the improved physical realism. (authors)