CFD Study of the Single-phase Subchannel Turbulent Mixing in Tight Lattice Geometry With Improved Wall Treatment

Abstract

This paper focuses on the numerical simulation of turbulence mixing phenomena in tight lattice geometries. The use of RANS for mixing phenomenon has been carried out. For large P/D subchannels, the influence of anisotropic of turbulence is not significant, and mixing rate between subchannels is dominated by turbulence eddy diffusion. The comparison between numerical results and experimental results proves that acceptable accuracy can be achieved for the mixing coefficient by steady-state and transient calculation with RANS models. However, for smaller P/D geometries, because of the strong anisotropy in the gap region, the contribution of macroscopic pulsation to mixing rate cannot be neglected any more, proved that the mixing rate is dramatically enhanced by the flow pulsation. Transient calculation with anisotropic turbulence model would be necessary.