An Implementation and Assessment of the Viscous Stress Model in the MARS Multi-Dimensional Component

MARS is a best-estimate thermal hydraulic systems analysis code with a multi-dimensional analysis capability. The MARS code is developed with the safety analysis as the prime application area and has a comprehensive range of models and components suitable for the simulation of nuclear reactor systems. The current developments in the nuclear industries and researches require accurate multi-dimensional analysis capabilities. However, the multi-dimensional model of MARS is based on a sub-channel formulation, and as such the geometric description is significantly limited. In order to alleviate such limitations, a new component based on the Cartesian and cylindrical coordinates, and the incorporating lateral convective terms and viscous stress terms have been added. The newly developed multi-dimensional component makes it possible to model a large bulk fluid volume in both the Cartesian and cylindrical coordinates. For the implementation of viscous shear stresses, Prandtl’s mixing length model is simply applied to obtain the turbulent viscosity. Several conceptual problems are described and solved using the new multi-dimensional component. The results were compared with the FLUENT calculations using the standard k-ε model. The comparison shows successful implementations and reasonable agreements with the FLUENT results.