Study on the characteristics of axial fluid excitation on fuel rods with spacer grids

Grids, supporting fuel rods, consist of dimples and mixing vanes. These complex structures cause turbulent flow field with complex vortex. The vibration of fuel rod by the high-velocity coolant may lead to grid to rod fretting (GTRF). In order to obtain the behavior of the fretting wear, it is crucial to investigate the induction mechanism of fuel rod by the flow field evolvement. In this paper, the effects of two structures with different geometric were discussed by numerical simulation. The generation and evolution of the fluid forces are analyzed in detail. The results show that the fluid forces mainly originate from the pressure asymmetry. Moreover, the clamping structures play a dominant role in both excitation and fluctuation of the fluid forces. The study obtained the effect of intrinsic structure on fluid excitation, and it can provide a basis for the fluid excitation boundary of the fretting wear of fuel rods.