Nonlinear vibrations and wear predictions of slender cylinders with loose support subjected to axial flows

Abstract

Flow-induced vibration of fuel rods subjected to axial flows frequently appears in nuclear engineering, which has been a significant scientific problem still unsolved. This paper simplifies the fuel rod as a slender cylinder with loose support in axial flows, and explores nonlinear dynamics of the slender cylinder through theoretical modeling. The dynamical model is constructed with consideration of impact and friction forces attributed by the loose support. The results show that the flutter critical flow velocity and wear rate are dependent on clearance size and position of the loose support. The flow velocity range of buckling becomes narrower while the range for flutter becomes wider with the increase of clearance size. The flow velocity range for buckled behavior is widened, the flutter flow speed range is reduced as the clearance position is varied from upward end to downward end of the cylinder. It is indicated that there are optimal values for clearance size and position of the loose support where the flutter critical flow velocity is much higher and the wear rate is lowest. The present study can provide a theoretical basis for predicting flow-induced vibrations and designing the loose support for fuel rods in the nuclear engineering.