Thèse soutenue

Étude expérimentale en tunnel hydrodynamique des instabilités de la cavitation par poche sur hydrofoil par la mesure spatio-temporelle du champ de pression pariétal
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Auteur / Autrice : Jean-Baptiste Leroux
Direction : Jean-Yves BillardJacques-André Astolfi
Type : Thèse de doctorat
Discipline(s) : Dynamique des fluides et des transferts
Date : Soutenance en 2003
Etablissement(s) : Nantes
Ecole(s) doctorale(s) : École doctorale mécanique, thermique et génie civil (Nantes)
Partenaire(s) de recherche : autre partenaire : Centrale Nantes (1991-....)

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Résumé

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The thesis deals with partial attached cavitation instabilities. Most of the study is experimental. Experiments were carried in a water tunnel, on a partially cavitating hydrofoil. The experimental conditions ranged from sheet cavities inception to unstable cavities and cloud cavitation. In the latter case, instabilities are induced by the periodical development of a re-entrant jet under the cavity, which leads to the detachment of very erosive vapour clouds, which are convected in the cavity wake. In addition, such flows are noisy and cause structure's vibrations. Wall pressure measurements, lift and drag measurements, and numerical video records were performed. In the case of stable cavities, the analysis shows a peak of the pressure fluctuations intensity in the closure region of the cavity. It originates from spatial fluctuations of the closure, small toward the mean cavity length, due to a condensation - vaporisation mechanism, which also leads to little vapour clouds convected in the cavity wake, but without re-entrant jet. A mean temporal analysis of the pressure signals puts in evidence the development of a travelling pressure wave from the cavity detachment point up to the closure, prior to the little clouds emission. In our opinion, this pressure wave is related to a travelling wave at the interface of the cavity, and the fluctuations of the closure can be explained by the break of this wave. These fluctuations are associated with frequency peaks, leading to Strouhal numbers, based on the mean cavity length [. . . ]