Axial Flow-induced Vibration Of A Twin Cylinder Configuration

Axial flow-induced vibration of a fuel rod bundle is an important research direction that attracts great attention in the field of nuclear engineering.The axial flow-induced vibration of fuel rods will destroy the structure of fuel rods and further cause nuclear fuel leakage accident.This work aims to investigate experimentally the vibration characteristics and the flow field around a flexible cylinder under different flow velocities and turbulence intensities.Experiments are performed in a vertical water tunnel where the flow velocity changes from 0 to 2.13 m/s.The turbulence intensity of the freestream flow is about 0.7%.The elastic cylinder is made out of room temperature vulcanizing(RTV)silicone rubber.The length and the diameter of the elastic cylinder are 605 and 14 mm,respectively.The maximum non-dimensional velocity u* is 4.23.The vibration of the elastic cylinder is measured at the center of elastic cylinder in y-and z-directions.Firstly,the effect of freestream velocity and the freestream turbulence intensity on the vibration characteristics and flow field around a single elastic cylinder is examined.Secondly,the effect of freestream velocity,the freestream turbulence intensity,and the gap ratio on the vibration characteristics and flow field around elastic cylinder within a twin-cylinder bundle are investigated.Note that both the LDV and PIV measurements are made simultaneously in order to resolve the fluid-structure interactions.The result shows that the vibration amplitude of flexible cylinder will become larger with increasing turbulence intensity,however the power spectral density shows that the dominant vibration frequency is unchanged,which means that the vibration mode will not be influenced by the turbulence intensity.When decreasing the gap ratio,the vibration amplitude of flexible cylinder also becomes large,but the dominant vibration frequency is unchanged.The strong interactions of fluid structure is regarded as a key point that enhance the vibration amplitude of flexible cylinder.