Effects of Bubble Size and Gas Density on the Shock-induced Collapse of Nanoscale Cavitation Bubble

Abstract

In this paper, we studied the nature of shockwave induced cavitation bubble collapse using molecular dynamics (MD) simulation. A major objective of this study is to determine how the variation of nanoscale bubble size and entrapped gas density affects the bubble dynamics. It is known that cavitation bubble collapse/implosion is a robust dynamic event that occurs when the potential energy of the acting pressure performs work in a rapid and violent manner. Usually, the energy converges into a significantly smaller region compared to the original cavitation bubble. While the mechanisms of cavitation have been studied for more than a century, recently, it has received renewed interests due to its connection with biomedical applications and traumatic brain injury (TBI). One of the common causes of TBI is blast-induced shock exposure. A shockwave, as a moving discontinuity of pressure, can lead to the formation and collapse of cavitation bubble and produce an impactful jet stream. The jet stream may cause a localized mechanical/thermal damage to the structures that come on its path. We have considered two different bubble sizes (10 and 20 nm). We found that different gas densities inside the cavitation bubble largely change the intensity of the aftermath. We also found the peak temperature during the collapse is linked to the bubble size but unrelated with the peak pressure.