Numerical Simulation of Phase Map Shift of Vibrating Cylinder at Low Reynolds Number

Abstract

The circular cylinder under a cross flow experiences boundary layer separation. It is a classical problem of fluid dynamics found in applications such as tall building structures, pipes, tubes, cables etc. Based on the Reynolds number range, periodic flow develops in the wake. The pattern of vortex shedding from the sides of the structure causes pressure fluctuations which may lead to structural vibration. The motion of structure leads to influence the flow pattern especially in the wake. In this paper we compare results for two cylinders having similar mass ratios for Reynolds number range of 2500-6000 with different structural damping. Initial validation of coupled fluid structure interaction simulations is obtained using comparison of vortex shedding frequencies and RMS amplitudes of both cylinders with experimental data. At low damping cylinder follows a random trajectory different from the cylinder having high damping ratio. With turbulent flow conditions the phase map of the lightly damped cylinder shows significant shift compared to laminar flow. It is observed that for the lightly damped structure, the dominating frequency of structural vibration matches its natural frequency for the range where St ~ 0.2 with non-uniform flow conditions.