Dynamics of Flexible Cylinders in Axisymmetrically Confined Axial Flow

Abstract

This paper describes experiments in which flexible cylinders placed centrally within a narrow cylindrical flow channel were subjected to axial flow. The dynamical behavior of such cylinders, either cantilevered or supported at both ends, is described, both in liquid and in simulated two-phase flows; the effect of several parameters, such as the annular confinement, was investigated. It was observed that, with increasing flow, the cylinder is subject sequentially to instabilities of increasing mode number, confinement severely destabilizing the system. The experimental observations are compared to a theoretical model for the dynamics of such systems. In the case of liquid flow, agreement is qualitatively good and quantitatively fair—keeping in mind the experimental difficulties. In the case of two-phase flows, theory and experiment do not agree.