Jet direction in bubble collapse within rectangular and triangular channels

Abstract

A vapor bubble collapsing near a solid boundary in a liquid produces a liquid jet that points toward the boundary. The direction of this jet has been studied for boundaries such as flat planes and parallel walls enclosing a channel. Extending these investigations to enclosed polygonal boundaries, we experimentally measure jet direction for collapsing bubbles inside a square and an equilateral triangular channel. Following the method of Tagawa and Peters (Phys. Rev. Fluids 3, 081601, 2018) for predicting the jet direction in corners, we model the bubble as a sink in a potential flow and demonstrate by experiment that analytical solutions accurately predict jet direction within an equilateral triangle and square. We further use the method to develop predictions for several other polygons, specifically, a rectangle, an isosceles right triangle, and a 30 • -60 • -90 • right triangle. arXiv:1910.08970v1 [physics.flu-dyn]

Cavity collapse near slot geometries

“…However, many evaluations of the velocity field would be required to determine the average velocity at the bubble surface numerically, so a different method is preferred. From the method employed by Tagawa & Peters (2018) and Molefe & Peters (2019), and from numerical testing, it is found that the velocity induced by mirror sinks at the bubble centre accurately describes the jet direction, independent of bubble radius. It is of interest to more fully understand this relationship and how it relates to the average surface velocity.…”

“…In this research a simplified boundary element method is used to predict the jet direction without resolving how the surface of the bubble moves over time. This is similar to the mirror sink model employed by Tagawa & Peters (2018) and Molefe & Peters (2019) to compute jet direction but with an infinite distribution of 'mirror' sinks along the geometry boundary as in boundary element methods. This method combines the simplicity of the mirror sink model for finding the jet direction with the geometric versatility of boundary element methods.…”

“…Previous research (Tagawa & Peters 2018;Molefe & Peters 2019) has shown that the jet direction is accurately predicted by the velocity that the mirror sinks induce at the position of the bubble centroid.…”

“…Studies on more complex geometries typically focus on interior geometries and exploit analytical tools such as the method of images (Kucera & Blake 1990; Tagawa & Peters 2018; Molefe & Peters 2019) or fully resolve the flow using complicated simulations (Wang et al 2020). There are also some studies that only investigate the geometry experimentally (Zhang et al 2017).…”

“…Some more complex geometries have been studied, such as parallel boundaries closed at one end (Brujan, Takahira & Ogasawara 2019), semi-infinite boundaries (Kucera & Blake 1990), near combinations of a free surface and an inclined flat boundary (Zhang et al 2017), inside a set of concave corners (Kucera & Blake 1990; Brujan et al 2018; Tagawa & Peters 2018; Wang et al 2020) and inside rectangular and triangular channels (Molefe & Peters 2019). A recent experimental study has investigated how a ridge-patterned structure can affect the bubble surface evolution and jet dynamics when a bubble is generated on the ridge and between the ridges (Kim & Kim 2020).…”