An Experimental Study on the Propagation of the Pressure Fluctuations Induced in a Tube Array under Forced Vibration

Abstract

Tube arrays subject to cross flow may exhibit large amplitude self-excited vibrations referred to as Fluidelastic Instability (FEI). Due to its potential for damaging the equipment in an extremely sort operational time, FEI is considered the most destructive mechanism within the flow induced vibration phenomena and has been extensively analysed in the literature in the past, however, the underlying mechanism for FEI onset remains unclear. A number of models, based on very different assumptions about the fluidmechal phenomenon has been developed with the common conclusion that the key factor for stability onset is in the relationship between tube motion and flow perturbation in terms of amplitude and phase. In the present study an experimental approach in a water channel especially designed and developed by the authors for the present investigation is proposed. The empirical set-up, consisting in a tube array in which one tube is forced to vibrate while pressure fluctuations due to is motion are monitored in several points of the array, allows to correlate tube motion and pressure perturbations. The FFT postprocess of those signals allows for the study of the perturbations propagation pattern and indeed in the understanding of the FEI phenomenon. Finally present experimental results will allow for the validation, adjust and improvement of a CFD model previously developed by authors.

Keywords

• fluidelactic instability
• flow-induced vibrations
• fluid structure interaction