Experimental Fluid-Force Coefficients for Wake-Induced Cylinder Vibration

Abstract

A mathematical model based on the unsteady-flow theory is presented for wake-induced vibration of an elastic circular cylinder in the wake of another circular cylinder. Motion-dependent fluid forces were measured for six cylinder arrangements. From measured fluid forces, fluid-damping and stiffness coefficients were calculated as a function of reduced flow velocity and oscillation amplitude. Once the fluid-force coefficients are known, the stability of an elastic cylinder in the wake of a stationary cylinder can be analyzed. The characteristics of dynamic instability were calculated for both coupled and uncoupled models. Results show that the unsteady-flow theory is a simple and useful model that can be applied to predict cylinder response. The model presented, based on the unsteady-flow theory and direct measurement technique, provides an adequate characterization of the fluid effects for a cylinder in the wake of another one.