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Operational Modal Analysis of a Triangular-Pitch Tube Bundle Subjected to Two-Phase Cross-Flow

Abstract : Flow-induced vibrations of tubes in two-phase heat exchangers are a concern for the nuclear industry. EDF has developed a numerical tool, which allows one to evaluate safety margins and thereafter to optimize the exchanger maintenance policy. The software is based on a semi analytical model of fluid-dynamic forces and dimensionless fluid force coefficients which need to be evaluated by experiment. A test rig was operated with the aim of assessing parallel triangular tube arrangement submitted to a two-phase vertical cross-flow: a kernel of nine flexible tubes is set in the middle of a rigid bundle. These tubes vibrate as solid bodies (in translation) both in the lift and drag directions in order to represent the so-called in-plane and out-of-plane vibrations. This paper outlines the experimental results and some detailed physical analysis of some selected points of the experiment series: the response modes are identified by means of operational modal analysis (i.e. under unmeasured flow excitation) and presented in terms of frequency , damping and mode shapes. Among all the modes theoretically possible in the bundle, it was found that some of them have a higher response depending on the flow velocity and the void fraction. Mode shapes allow to argue if lock-in is present and to clarify the role of lift and drag forces close to the fluidelastic instability.
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Contributeur : Enrico Deri Connectez-vous pour contacter le contributeur
Soumis le : vendredi 1 juin 2018 - 09:25:53
Dernière modification le : vendredi 21 décembre 2018 - 11:06:03





Enrico Deri. Operational Modal Analysis of a Triangular-Pitch Tube Bundle Subjected to Two-Phase Cross-Flow. Journal of Pressure Vessel Technology, American Society of Mechanical Engineers, 2018, 140 (3), ⟨10.1115/1.4038725⟩. ⟨hal-01804695⟩



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