Numerical study on flow-induced vibration of two-degree-of-freedom staggered circular cylinders at subcritical Reynolds numbers

Abstract

In this study, the flow-induced vibration of two-degree-of-freedom staggered circular cylinders at subcritical Reynolds numbers is studied numerically with overset dynamic mesh. The streamwise spacing ratio Sx/D of 4 and the transverse spacing ratio Sy/D ranging from 0 to 2 are employed to explore the influence of staggered arrangement on the vibrations and fluid forces of cylinders. It is found the upstream cylinder mainly experiences the vortex-induced vibration while vortex-induced and wake-induced vibrations happen for the downstream one, which may be interfering or independent depending on the transverse spacing of cylinders. The phase lag between the displacement and fluid force of the downstream cylinder changes from 0° to 180° with the increasing of inflow velocity, which leads negative add mass and serves as the reason of wake-induced vibration. The theoretical formulae to estimate the critical velocity, fluid coefficient and vibration amplitude of wake-induced vibration are proposed and validated by the numerical simulations.