Abstract
In many practical submerged objects, various types of cavitation such as bubble, sheet, and cloud cavitation occur according to flow conditions. In spite of numerous theoretical, numerical, and experimental studies, there are still many problems to be solved such as induced noise and damage potential due to cavitation. In this paper, an experimental investigation on coherent structures and induced noise characteristics of partial cavitation on a two-dimensional hydrofoil is presented. Experiments that focused on the dynamics of cavitation clouds were conducted in a cavitation tunnel. Using high-speed visualization, the series process consisting of inception, growth, and desinence of the partial cavity was investigated. The noise generated during the process was also measured, and the correlation with the cavity pattern was examined. The results show that the periodic behavior of cavitation clouds is directly reflected in the noise characteristics. In addition, the visualization of coherent structures within the sheet and cloud cavity provides a qualitative understanding of hairpin vortices and their packets, which play a dominant role in turbulent cavitating flows.
Highlights
Cavitation occurs irresistibly on the low-pressure surfaces of submerged bodies such as hydrofoils, marine propellers, and turbomachinery blades
Hydrodynamic cavitation takes different forms as it develops from inception, and the patterns can be divided into three types of cavities: bubble cavity, partial cavity, and vortex cavity at the tip of three-dimensional foil
Sheet and cloud cavitation have been major concerns, and many studies have been conducted to figure out related problems, namely the physical process of cavitation inception, the structural process of cavity formations, and the hydrodynamics and acoustics involved in the production and collapse of partial cavitation
Summary
Cavitation occurs irresistibly on the low-pressure surfaces of submerged bodies such as hydrofoils, marine propellers, and turbomachinery blades. As the cavitation number decreases further, sheet cavitation becomes longer and begins to shed cloud cavitation, which is periodically pulsating and causes a great deal of noise and vibration, damage to the surface, and a loss of efficiency of the object. For this reason, sheet and cloud cavitation have been major concerns, and many studies have been conducted to figure out related problems, namely the physical process of cavitation inception, the structural process of cavity formations, and the hydrodynamics and acoustics involved in the production and collapse of partial cavitation. Many theoretical and experimental studies have been done in two areas: one is to find physical aspects of the phenomenon, the other to estimate its harmful effects
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