Elongated bubble velocity estimation in vertical liquid-gas flows using flow-induced vibration.

• Non-stationary vibration was identified on ducts conveying two-phase flows. • Elongated bubble velocity determined by using different methods on the vibration signal. • Different experimental procedures to identify and validate the technique. • Extensive test-matrix to evaluate the vibration signal over different flow conditions. The multiphase flow occurs in various major industrial fields and nature. Furthermore, due to the single and multiphase flow characteristics, they generate vibration on the structure conveying or subjected to the flow. This paper investigates in an experimental apparatus, the possibility to use the flow-induced vibration from a vertical liquid-gas two-phase flow conveyed by a pipe to obtain the elongated bubble velocity. The vibration signal analysis in time domain showed that the structural excitation due to the elongated bubble rising in the stagnant liquid was significant to be distinguished from other excitations. The time-frequency analysis of slug and churn flow showed a significant amplitude variation in a specific frequency band. Finally, it was possible to obtain the elongated bubble velocity with reasonable accuracy by cross-correlating the envelope of a vibration signal filtered in a particular frequency band of two accelerometers. Thus, this paper presents a non-invasive and simple to mount technique to estimate the elongated bubble velocity in stagnant and moving liquid conditions. [ABSTRACT FROM AUTHOR]