A Numerical Investigation of Turbulent Interchange Mixing of Axial Coolant Flow in Rod Bundle Geometries

This article is concerned with modeling turbulent interchange mixing within rod bundle arrays. Using a three-dimensional numerical solution, the characteristics and appropriateness of an isotropic κ–∊ turbulence model were investigated by comparing code predictions with experimental results. A novel methodology for solving for the fluid temperature field was also developed. Application of this methodology resulted in significant savings in computational effort for the problem of interest. Analysis of the results indicated that the isotropic model accurately predicted the radial component of turbulent eddy viscosity, but underpredicted the azimuthal component. As a result, radial diffusion processes (such as pressure drop) were predicted accurately, but azimuthal diffusion processes (such as turbulent interchange mixing) were underpredicted. Higher-order turbulence models such as algebraic stress models are therefore required if the details of the turbulent mixing are to be resolved.