Bubble dynamics near a locally curved region of a plane rigid wall

Abstract

The dynamics of a bubble near a local axisymmetric convexity or concavity, cosine-like in the axial section, on a plane rigid wall is studied in the regime with the formation of a cumulative liquid jet directed to the wall. The study is performed by the boundary element method. Main attention is focused on the bubble collapse characteristics at the moment tc when the jet impacts on the bubble surface part near the wall, namely on the jet tip velocity and radius, the internal bubble pressure, the distance between the bubble and the uneven region of the wall, etc. These characteristics are of interest since they to large extent determine the destructive potential of cavitation. The dependences of these characteristics on the radius of the non-plane region of the wall, the depth of the concave region and the height of the convex region, and the local character of the wall unevenness have been investigated. To estimate the effect of the local character of the wall unevenness, the cases of completely concave and convex walls in the form of blunt conical surfaces are used for comparison. It has been found, in particular, that with changing radius of the convex region of the wall, the bubble shape at the moment tc varies significantly: the shape diversity includes the profiles with a gas microcavity in front of the impacting jet tip, an emerging second oppositely-directed jet, and a quite large area of the jet tip impact at its beginning.

Bubble nucleation and jetting inside a millimetric droplet

“…The parallel found between cases with dissimilar curvature of the liquid surface suggests that, contrarily to the reported observations for bubbles collapsing near concave solid surfaces (Aganin et al 2022), R d does not have a dominant role in the particular jetting regime adopted by the cavities when the bubbles are located near the free boundary. This statement was confirmed by the numerical simulations depicted in figure 12.…”

“…2018 a ; Li et al. 2019 b ; Aganin, Kosolapova & Malakhov 2022) like pillars (Kadivar et al. 2021; Koch et al.…”

“…The jet dynamics is frequently characterised by a stand-off parameter (Lindau & Lauterborn 2003;Supponen et al 2016;Lauterborn et al 2018) computed as the ratio of the distance between the bubble nucleation position and the boundary (d) and the maximum radius attained by the bubble after its creation (R max ). If the cavity collapse occurs next to boundaries other than a plane, for instance, irregular or curved surfaces (Tomita et al 2002;Blake, Leppinen & Wang 2015;Wu et al 2018a;Li et al 2019b;Aganin, Kosolapova & Malakhov 2022) like pillars (Kadivar et al 2021;Koch et al 2021b), fibres (Mur et al 2023), corners (Mahmud, Smith & Walmsley 2020;Zhang et al 2020), crevices (Andrews, Fernández Rivas & Peters 2020;Trummler et al 2020), perforated plates (Gonzalez-Avila, Song & Ohl 2015; Reese et al 2022) or spheres (Zhang et al 2018;Li et al 2019a;Zevnik & Dular 2020;Ren et al 2022), the anisotropy does not have one predominant direction and, thus, the use of a single stand-off parameter (e.g. d/R max ) is no longer sufficient to fully characterise the system.…”

Investigation on the effects of an elliptical wall on the dynamic behaviors of a bubble restricted by two parallel plates

“…The dynamics of the spherical bubbles near rigid boundary have been widely researched. For walls with curvature, cavitation research has mainly focused on curved boundaries [11] , [12] , [13] , [14] , [15] , [16] , [17] , [18] , [19] and particles [20] , [3] , [21] , [22] , [23] , [24] , [25] , [26] . In the case of curved boundaries, the effects of the wall curvature were considered by Takahira et al [11] , who constructed a dynamic model of a spherical bubble near a curved wall and observed a positive correlation between the wall curvature and the pressure at the center of the wall.…”