Measurement of fluctuating fluid pressure exerted on the walls of a tube bundle
Résumé
Flow-induced vibrations (FIV) are particularly important as a problem field in reactor technology. Beyond the need to prevent fluidelastic instability phenomena which can lead to rapid failures, it is necessary to also account for the long-time effects of the flow turbulence excitations. For instance, the grid-to-rod fretting wear is still a worldwide dominant fuel rod leaker mechanism [1] and its main root cause has been identified as fuel rod vibration induced by the turbulent flow [2]. A large effort is thus devoted to the prediction of the vibration response of a tube, from a fuel assembly or a steam generator, subjected to turbulent axial and/or transverse flow, through the advanced mechanical modelling of a multi-supported beam under a representative excitation to be fully determined. The need remains for an accurate knowledge of the spectral content and spatial distribution of the flow excitation [3], usually obtained from experiments, where the forces are either directly measured [4] or inferred from the system responses [5].Even if computational fluid dynamic (CFD) simulations for highly turbulent flows already produce results [6, 7, 8, 9], some innovative instrumentation is yet required to provide accurate validation data in terms of magnitude, spectral content and spatial distribution of the fluctuating pressure on the tube wall, known from the literature to represent about 90% of the force applied by the fluid.The current paper is therefore dedicated in the first part to the presentation of the development of such a measuring device. In the second part, two experimental configurations implementing this technology are introduced and in the third part, some results are presented and discussed.
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