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Mechanism of Cloud Cavitation Generation on a 2-D Hydrofoil

Sakoda, Motoyuki and Yakushiji, Ryo and Maeda, Masatusgu and Yamaguchi, Hajime (2001) Mechanism of Cloud Cavitation Generation on a 2-D Hydrofoil. In: CAV 2001: Fourth International Symposium on Cavitation, June 20-23, 2001. (Unpublished)

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When a sheet cavity on a hydrofoil section attains a certain size, it starts violent periodical oscillation shedding a harmful cloud cavity downstream at each oscillation cycle. This phenomenon is due to the occurrence of the re-entrant jet. In this paper, the behavior of the re-entrant jet was observed in detail using a transparent foil section model and a high-speed video camera. Time variation of pressure distribution on the foil was measured simultaneously. It was found that the re-entrant jet can start at any point in sheet cavity elongating stage. Even two re-entrant jets can appear in one cycle. When a re-entrant jet is generated upstream, the jet velocity is lower compared to the case when a re-entrant jet is generated downstream. The jet velocity is almost constant at the value determined by the location of the generation. As a result, the cavity oscillation cycle becomes constant when it is normalized by the sheet cavity surface velocity and the maximum sheet cavity length. The jet velocity is calculated from the pressure gradient at the sheet cavity T.E., using a simple theoretical model. The calculated jet velocity agrees with the measurement, showing that the jet velocity increases as its generation point shifts downstream. It is possible that pressure gradient at the sheet cavity T.E. is the driving force of re-entrant jet.

Item Type:Conference or Workshop Item (Lecture)
Subject Keywords:cloud cavitation, sheet cavitation, foil section, re-entrant jet,high-speed video observation, pressure gradient
Record Number:CAV2001:sessionA9.004
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Usage Policy:The papers of this symposium proceedings are protected by copyright, retained by the authors. Authors control translation and reproduction rights to these works. However, readers are granted permission for individual, educational, research and non-commercial reproduction, distribution, display and performance of this work in any format. This permission is in addition to rights of reproduction granted under Section 107, 108, and other provisions of the U.S. Copyright Act.
ID Code:72
Deposited By: Imported from CAV2001
Deposited On:01 May 2001
Last Modified:03 Oct 2019 22:49

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