Numerical simulation of flow resistance characteristics in a rod bundle channel under rolling conditions

Abstract

Flow resistance characteristics in a 3 × 3 rod bundle channel under rolling motion are investigated by numerical simulation to overcome the limitation of experimental conditions and measurement methods. Severe rolling conditions are selected to make up for the lack of test range. The local parameters, including flow field, temperature field and wall shear stress are given to analyze the influence mechanism of the rolling motion on friction resistance of the rod bundle channel. Under rolling conditions, the absolute value of flow rate does not influence the fluctuation amplitude of frictional pressure drop when inlet flow rate does not fluctuate. Additional pressure drop is the main factor affecting the fluctuation amplitude of frictional pressure drop under rolling conditions. When the rolling motion becomes severe, the velocity deviation increases, while it has no obvious influence on velocity peak value within cross section. Increasing the flow rate weakens the effect of rolling motion on axial velocity distribution. The variation of flow rate does not affect the magnitude and distribution of radial velocity, and the radial secondary flow intensity is mainly determined by the intensity of rolling motion. Different from velocity distribution, the wall shear stress distribution is obviously affected by rolling motion and is unconnected with flow rate, while the flow rate affects the relative value of wall shear stress. Under the same rolling parameters, the variation range of boundary layer thickness increases with decreasing flow rate, which leads to an increase in the relative variation range of wall shear stress with decreasing flow rate.