Experimental evaluation of methodologies for single transient cavitation bubble generation in liquids

Darjan Podbevšek,Matevž Dular,Rok Petkovšek,Jure Podobnikar,Žiga Lokar

doi:10.1007/s00348-021-03260-1

Abstract

Single bubble dynamics are of fundamental importance for understanding the underlying mechanisms in liquid–vapor transition phenomenon known as cavitation. In the past years, numerous studies were published and results were extrapolated from one technique to another and further on to “real-world” cavitation. In the present paper, we highlight the issues of using various experimental approaches to study the cavitation bubble phenomenon and its effects. We scrutinize the transients bubble generation mechanisms behind tension-based and energy deposition-based techniques and overview the physics behind the bubble production. Four vapor bubble generation methods, which are most commonly used in single bubble research, are directly compared in this study: the pulsed laser technique, a high- and low-voltage spark discharge and the tube arrest method. Important modifications to the experimental techniques are implemented, demonstrating improvement of the bubble production range, control and repeatability. Results are compared to other similar techniques from the literature, and an extensive report on the topic is given in the scope of this work. Simple-to-implement techniques are presented and categorized herein, in order to help with future experimental design. Repeatability and sphericity of the produced bubbles are examined, as well as a comprehensive overview on the subject, listing the bubble production range and highlighting the attributes and limitation for the transient cavitation bubble techniques.Graphic abstract

Highlights

The phenomenon known as cavitation is the emergence of vaporous voids in the liquid as its intermolecular cohesive bonds are overcome
For the tube arrest method (TAM), the lifetimes are extended considerably compare to theory, due to the initial pressure wave recoils traveling up and down the tube liquid column, affecting the bubble dynamics and probably causing the instabilities which are often seen on the bubble surface (Fig. 7e)
Four vapor bubble generation methods were tested for their governing parameters, as well as the bubble response to liquid temperature and electrolytic conductivity

Summary

Introduction

The phenomenon known as cavitation is the emergence of vaporous voids in the liquid as its intermolecular cohesive bonds are overcome. It is often generalized as the appearance of bubbles in the liquid when the pressure drops below liquid vapor pressure It often accounts for the accompanying degassing and the expansion of already present uncondensed gas nuclei in the liquid (Trevena 1984), as the two are hard to dissociate; thermodynamically, cavitation is defined as the phase change from liquid to vapor. It was found that dynamics of these bubbles are responsible for many unwanted, as well as beneficial effects of cavitation, which in recent years started attracting ever greater attention in scientific and engineering fields The former range from mild effects such as noise emissions and vibrations, to efficiency drop and even erosion of solid walls (Dular and Petkovšek 2015; Luo et al 2016; Dular et al 2019), while positive effects are numerous, stemming from the inherent energy focusing properties of cavitation bubble dynamics. These have applications from chemical (Zupanc et al 2014; Dular et al 2016; Gągol et al 2018) and biological (Šarc et al 2016; Kosel et al 2017; Zupanc et al 2019) wastewater treatment, material productions (Qiu et al 2019), cleaning (Verhaagen and Fernández Rivas 2016), process intensification (Sajjadi et al 2015; Zhang et al 2016b), to a wide field of fundamental research in physics (Azouzi et al 2013), chemistry (Grieser et al 2015; Nikitenko and Pflieger 2017; Podbevsek et al 2018; Podbevšek et al 2021), biology (Patek and Caldwell 2005; Iosilevskii and Weihs 2008; Vilagrosa et al 2012) and medicine (Stride and Coussios 2010)

Results

Discussion

Conclusion