High speed observation of damage created by a collapse of a single cavitation bubble

Dular, Matevž (author), Požar, Tomaž (author), Zevnik, Jure (author), Petkovšek, Rok (author)

One of the remaining open questions in cavitation erosion research is the one on the importance of the microjet and the shock wave on the formation of the pit. Up until now, no successful attempt has been made to study this in detail, mainly because the damage could only be detected and evaluated after several successive bubble collapses. A bubble with a maximum diameter of up to 3.3 mm was created during photoionization using a Nd:YAG laser. The damage was observed on a 9 µm thick aluminum foil attached to a glass substrate. Two high speed cameras were simultaneously used. One captured the dynamics of the bubble, while the other recorded the damage of the foil. We also observed the collapse of a bubble in the presence of shear flow, where most of the damage is created by the microjet mechanism. Sometimes, the collapse of the bubble rim, at the rebound of the initial bubble causes pits in a well-known circular pattern. From the recordings at the very fastest acquisition rate, we determined that the material deforms and then partially relaxes, while a significant deformation remains. The whole process is only 2-3 µs long.

• Language: English
• Keywords: cavitation erosion, single bubble, shear flow, high speed observation
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Author Accepted Manuscript
• Publication date: 08.11.2018
• Year: 2019
• Number of pages: Str. 13-23
• Numbering: Vol. 418/419
• PID: 20.500.12556/RUL-138415
• UDC: 532.528(045)
• ISSN on article: 0043-1648
• DOI: 10.1016/j.wear.2018.11.004
• COBISS.SI-ID: 16342555
• Publication date in RUL: 20.07.2022

Record is a part of a journal

• Title: Wear
• Shortened title: Wear
• Publisher: Elsevier
• ISSN: 0043-1648
• COBISS.SI-ID: 5374213

Secondary language

• Language: Slovenian

Abstract

Eno izmed preostalih odprtih vprašanj pri raziskovanju kavitacijske erozije je vprašanje o pomenu mikrocurka in udarnega vala pri nastanku poškodb. Do zdaj ni bilo nobenega uspešnega poskusa, ki bi to podrobno preučil, predvsem zato, ker je bilo škodo mogoče zaznati in oceniti šele po več zaporednih kolapsih mehurčkov. Med fotoionizacijo z uporabo laserja Nd:YAG je bil ustvarjen mehurček z največjim premerom do 3,3 mm. Poškodbe smo opazovali na 9 µm debeli aluminijasti foliji, pritrjeni na stekleno podlago. Hkrati sta bili uporabljeni dve hitri kameri. Ena je zajemala dinamiko mehurčka, druga pa beležila poškodbe na foliji. Prav tako smo opazovali tudi kolaps mehurčka ob prisotnosti strižnega toka, kjer večino škode povzroči mikrocurek. Včasih kolaps kavitacijskega obroča pri odboju začetnega mehurčka povzroči poškodbe v obliki dobro znanega krožnega vzorca. Iz posnetkov z najvišjo hitrosti zajemanja slik smo ugotovili, da se material deformira in nato delno relaksira, pri čemer ostane zaznavna deformacija. Celoten postopek traja le 2-3 µs.

• Keywords: kavitacija, erozija, mehurčki