Numerical simulation of flow resistance characteristics in a rod bundle channel under vertical and inclined conditions

摘要

Numerical simulation of flow resistance characteristics in a 3 × 3 rod bundle channel under vertical and inclined conditions is carried out. Compared with experimental results, it is verified that Reynolds stress model with enhanced wall treatment can accurately calculate flow parameters in rod bundle. Under vertical conditions, flow boundary layer at high Reynolds number is relatively thinner and radial velocity vector at interface of each subchannel is basically parallel to dividing line or opposite direction. Mainstream velocity distribution in channel under heating conditions is more uniform and radial secondary flow is more likely to occur than that under adiabatic conditions. Axial velocity near wall is a dominated factor to determine wall shear stress. Under inclined conditions, deviation of overall flow velocity distribution is more obvious and relative intensity of natural convection is more significant at low Reynolds number conditions compared with high Reynolds number conditions. Main mechanism of increase in frictional resistance due to inclination is that natural convection caused by thermal stratification changes flow velocity distribution of each sub-channel. Additionally, natural convection increases radial secondary flow area, broadens wall shear stress distribution and also increases average wall shear stress of cross section.