Abstract: Flow-induced vibration will happen when the fuel assemblies in a reactor are flushed by the coolant at a high speed. And vibration of fuel rod cladding and spacer grid strips will lead to wear of fuel assemblies, which affects the operation security of nuclear power plant. In order to study the characteristics and the methods of flow-induced vibration of spacer grid strips, a flat stainless strip without structure is employed to carry on the flow-induced vibration experiments. A laser Doppler vibrometer is used to measure the vibration characteristics of the strip under waterflow conditions. The test results show that the “lock-in” phenomenon occurs when the frequency of vortex-induced vibration is near to the natural frequency. Vortex-induced vibration frequency is linear with the flow velocity within a certain flow rate range. Furthermore, the natural frequency of the flat strip in water is well predicted by applying wet modal simulation.

Key words: flat strip; flow-induced vibration; vortex-induced vibration; wet modal