Simulation study of turbulent mixing characteristics of tight lattice with triangular arrangement under blockage condition

Abstract

The study of turbulent mixing in the gaps of fluid sub-channels in the tight lattice under blockage conditions is of great significance to the prediction of the thermal-hydraulic behavior of fuel assemblies under accident conditions. The CFD method was used to simulate the fluid flow phenomenon in the blockage condition in the tight lattice, and the velocity field and the turbulent mixing coefficient distribution in the section and downstream of the blockage under different blockage conditions were further compared and analyzed. The analysis results show that the blockage mainly affects the flow field of the sub-channel where it is located and the adjacent sub-channels. The turbulent mixing coefficient in these channels will increase significantly; when the sub-channel blockage rate is small, the turbulent mixing coefficient downstream of the blockage will be reduced; the short length will make the flow field near the top of blockage segment more complicated. The obtained changes of transverse and axial turbulent mixing coefficients under different blockage conditions can provide a reference for the parameter setting of the sub-channel analysis program.