Dynamics of a hanging fluid-discharging pipe subjected to reverse external flow: An experimental investigation

Abstract

The present paper discusses and analyzes experiments on the dynamics of hanging cantilever tubular beams conveying fluid downwards and subjected to partially-confined reverse external axial flow. A bench-top-size facility, consisting of a reservoir filled with water, a hanging flexible pipe conveying fluid downwards and a shorter outer rigid tube surrounding the pipe at its upper portion containing an upwards flow, was utilized. A non-contacting optical approach was employed to obtain the displacement time-series of pipe motions from which, using qualitative and quantitative nonlinear dynamics tools, the nature of the motions was explored. The oscillatory motions observed were found to be unsteady with both periodic and chaotic content. The influence of some system parameters on the dynamics, namely, external flow confinement, pipe slenderness, pipe material, placement of a constraint at the external annular flow inlet/outlet, and eccentric positioning of the outer rigid tube relative to the central pipe, was examined. It was found that varying the system parameters in some cases gives rise to quite interesting qualitative or quantitative changes in this Fluid–Structure Interaction (FSI) system.