Experimental investigation of three distinct mechanisms for the transition from sheet to cloud cavitation

Zhang, Guangjian (author), Zhang, Desheng (author), Ge, Mingming (author), Petkovšek, Martin (author), Coutier-Delgosha, Olivier (author)

The conventional high-speed images of cavitation with a set of X-ray phase contrast images reveal the presence of three different types of mechanisms responsible for large cloud shedding: re-entrant jet mechanism, condensation shock wave mechanism, and collapse-induced pressure wave mechanism. At higher cavitation numbers, the sheet cavity is relatively short and the cavity detachment is a consequence of a re-entrant jet pinching off the cavity from its leading edge. At lower cavitation numbers, the re-entrant jet plays a smaller role in the cavitation instabilities and the primary reason for periodic cloud shedding is the condensation shock mechanism where a void fraction discontinuity propagates upstream until collapsing the entire cavity. If the amount of shed vapour cloud reaches a certain extent, the collapse will emit a pressure wave strong enough to disturb the growing cavity, and subsequently make it detached from the wall. This is the third mechanism observed in the experiments. We point out the inappropriate classification of combining condensation shock and collapse-induced pressure wave mechanisms in the literature, since we identify pronounced differences between them: (i) the pressure increase across the condensation front is very weak (a few kPa) while the amplitude of collapse-induced pressure wave can be hundreds of kPa, (ii) the travelling velocity of the collapse-induced pressure wave within the cavity is much faster than the condensation shock, and (iii) the collapse-induced pressure wave does not result in an obvious discontinuity in void fraction when it propagates through the cavity, in contrary to the condensation shock.

• Language: English
• Keywords: cavitation, cavitation instability mechanism, condensation shock, re-entrant jet, pressure wave
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Publication date: 15.11.2022
• Year: 2022
• Number of pages: 16 str.
• Numbering: Vol. 197, art. 123372
• PID: 20.500.12556/RUL-139721
• UDC: 532
• ISSN on article: 0017-9310
• DOI: 10.1016/j.ijheatmasstransfer.2022.123372
• COBISS.SI-ID: 120414211
• Publication date in RUL: 06.09.2022

Record is a part of a journal

• Title: International journal of heat and mass transfer
• Shortened title: Int. j. heat mass transfer
• Publisher: Elsevier
• ISSN: 0017-9310
• COBISS.SI-ID: 3064335

Secondary language

• Language: Slovenian
• Keywords: kavitacija, kavitacijska nestabilnost, kondenzacijski šok, povratni tok, tlačni val