Etude des forces fluctuantes dans des elements de tuyauterie soumis a des ecoulements diphasiques internes

The purpose of the present work is to study the fluctuating forces that occur in piping elements subjected to internal two-phase flow. The experimental approach consists of subjecting five U-tubes of several geometries to a series of air-water mixtures and to measure (i) vibration response, (ii) excitation forces and (iii) fluctuating properties of two-phase flow.; Experimental results show that the observed vibration behavior is caused by a resonance phenomenon between first modes of U-tubes and periodic components of forces induced by fluctuations of the axial momentum flux of two-phase flow.; The excitation force spectra are typically of triangular shape, with a predominant frequency that increases proportionally to flow velocity. The force spectra can generally be correlated as a normalized power spectral density as a function of a dimensionless frequency.; Random vibration theory can be used to predict the response within an error margin of 50%.; The observed fluctuating properties of the forces agree with recent results on the characteristics of periodic structures in two-phase flow. (Abstract shortened by UMI.)...