Rebounds of deformed cavitation bubbles

Abstract

Presented here are experiments clarifying how the deformation of cavitation bubbles affects their rebound. Rebound bubbles carry the remaining energy of a bubble following its initial collapse, which dissipates energy mainly through shock waves, jets, and heat. The rebound bubble undergoes its own collapse, generating such violent events anew, which can be even more damaging or effective than at first bubble collapse. However, modeling rebound bubbles is an ongoing challenge because of the lack of knowledge on the exact factors affecting their formation. Here we use single-laserinduced cavitation bubbles and deform them by variable gravity or by a neighboring free surface to quantify the effect of bubble deformation on the rebound bubbles. Within a wide range of deformations, the energy of the rebound bubble follows a logarithmic increase with the bubble's initial dipole deformation, regardless of the origin of this deformation. 1 arXiv:1810.12287v1 [physics.flu-dyn] 29 Oct 2018 derstanding the underlying physics has motivated numerous studies to look at simplified case studies, especially involving the first collapse of single cavitation bubbles in various conditions. A great deal is indeed known about these bubbles and how they are able to emit microjets moving at hundreds of meters per second [11,12], shock waves with peak pressures reaching thousands of atmospheres [13][14][15], and luminescence, i.e., light emission due to the extreme heating of the bubble interior reaching thousands of degrees in temperature [16,17].Our understanding of these processes comes from the combination of experimental studies, often using laser- [13,[18][19][20], spark-[21-23], or ultrasound-induced [24, 25] cavitation bubbles; numerical studies typically using boundary integral methods [18,[26][27][28][29][30] and domain methods [31][32][33][34][35]; and analytical studies, most of them considering bubbles collapsing spherically [36][37][38][39][40][41][42] but some also tackling non-spherical bubble shapes, for example, by using the concept of Kelvin impulse [43,44].Non-sphericity adds a lot of complexity to the modeling of the bubble collapse. We also do not precisely know the composition, the quantity, the source, or the behavior of the gaseous contents of a typical cavitation bubble in its most extreme collapse conditions, making accurate modeling even more challenging. During the final stages of the collapse, these bubble contents are violently compressed and act as a spring, making the bubble interface bounce off them and forming thus a rebound bubble. The rebound's characteristics (for instance, its geometry or distance to a surface) often vary from those of the first bubble oscillation, and its ensuing collapse can lead to effects that are comparable or even more damaging. It is therefore important to understand the physics underlying multiple bubble oscillations, which is not yet fully understood. Many theoretical and numerical studies rely on experimental observations to model the rebound bubble, of which the formation ...

What We Learned from Cavitation Bubbles in Microgravity

“…We provide here a selection of the most important results obtained with the experimental setup explained above. Interested readers may refer to the more indepth publications by the Flash and Splash team [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25].…”

“…I did not know that this meeting of September 2004 was the start of a long and fruitful research activity on bubble dynamics in microgravity, which continues today. Following the first participation in the students flight campaign, we took part in eight research campaigns with the involvement of four PhD students, M. Tinguely [2], O. Supponen [3], A. Sieber and D. Preso with many other master students and technicians. This innovative and exciting research, which received financial supports from the Swiss National Science Foundation, the European Union and many other governmental and private institutions, produced a strong impact within the scientific community and beyond.…”

“…Top: visualization of a laser-induced bubble dynamics (112 μs inter-frame); middle: measured bubble radius (blue circles), along with theoretical predictions; bottom: pressure signal measured far from the bubble centre (reproduced from[3]). …”

A New Measurement Based on HPB to Measure the Wall Pressure of Electric-Spark-Generated Bubble near the Hemispheric Boundary

“…When the collapse of a bubble occurs near a structure, the structure will bear an impact due to the collapsing bubble [3]. At the same time, high-speed liquid jets can also occur in the final stage of bubble collapse [4,5]. erefore, the damage characteristics of bubbles to adjacent structures are critical in fluid mechanics.…”

Cavitation induced by shock wave focusing in eye-like experimental configurations

“…Indications that the refocused shock waves may play an important role in laser-induced, breakdown-based medical procedures in human eyes are scattered over the literature. It is well known that when laser breakdown is generated in water close to its free surface, smaller secondary bubbles appear within the laser path after the shock wave reflected from the free surface overpasses the volume irradiated by the laser pulse [18,19]. Additional focusing of shock waves from concave surfaces, such as from the internal walls of round flasks [20], rising free water surfaces [21], free surfaces of liquid jets [22] and water drops [23] make the secondary cavitation even more pronounced.…”