Experimental investigation on two-phase cross-flow-induced vibration of a cylinder in a confined channel

Abstract

Interactions between cylindrical structures and two-phase flows is a major concern for industrial applications, especially where cross-flows may cause damages, in heat exchangers for example. In order to understand the phenomenon of vibrations induced by two-phase flows, many experiments were conducted with reduced-scale models. In single-phase flow, the phenomenon has been characterized but is still a challenge numerically. In terms of two-phase flow, the effect of the two-phase flow regime adds more difficulties to explain the resulting phenomena in terms of vibrations. Experiments have been conducted focusing on vibrations mainly and flow pattern. To address this complex topic, the authors propose to study the impact of flow-pattern on vibration on a simpler geometry, presenting the advantages to be able to catch local scale phenomena and to be an interesting test case for CFD scale validation. The present paper focuses on a geometry which has been extensively studied in single-phase flow : flow-induced vibration of a single cylinder. An experiment with an upward air/water flow for void fractions, ranging from 10% to 80%, with two-phase flow characterization based on a wire-mesh sensor and a bi-optical sensor has been carried out in addition to vibration measurements. In terms of two-phase flow, the main behaviors for low void fractions, described in literature, are first reproduced and then extended to higher void fractions to be studied. In terms of vibration, the role of void fraction and flow-pattern is highlighted.