Investigation on the cavitation bubble collapse and the movement characteristics near spherical particles based on Weiss theorem

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

The present paper investigates the dynamic behaviors of a bubble restricted by two parallel plates near an elliptical wall. The typical experimental phenomena of the bubble are recorded employing the high-speed photography and a theoretical Kelvin impulse model is established. The impacts of the spatial position and the curvature of the wall on the bubble collapse behaviors are quantitatively investigated through the theoretical model and verified against the experimental results. The Kelvin impulse intensity and the direction during the bubble collapse process are compared and discussed for different elliptical-shaped walls. The main conclusions include: (1) During the bubble collapse process, the phenomenon of the bubble uneven splitting is discovered. (2) At different spatial positions and wall curvatures, the bubble collapse jet angle, movement distance, and velocity are in good agreement with the theoretical Kelvin impulse predictions. (3) As the short-to-long axis ratio increases, the differences in the distributions of the Kelvin impulse intensity and the direction near the elliptical wall gradually become larger, and the range of the influence of the impulse intensity expands.

Experimental study on influence of particle shape on shockwave from collapse of cavitation bubble

The bubble dynamics under the influence of particles is an unavoidable issue in many cavitation applications, with a fundamental aspect being the shockwave affected by particles during bubble collapse. In our experiments, the method of spark-induced bubbles was used, while a high-speed camera and a piezoresistive pressure sensor were utilized to investigate how particle shape affects the evolution of shockwaves. Through the high-speed photography, we found that the presence of the particle altered the consistency of the liquid medium around the bubble, which result in the emitting of water hammer shockwave and implosion shockwave respectively during the collapse of the bubble. This stratification effect was closely related to the bubble-particle relative distance φ and particle shape δ. Specifically, when the bubble-particle relative distance φ < 1.34 e-0.10δ, particles disrupted the medium consistency around the bubbles and led to a nonspherical collapse and the consequent stratification of the shockwave. By measuring the stratified shockwave intensity affected by different particle shapes, we found that the stratified shockwave intensity experienced varying degrees of attenuation. Furthermore, as the particle shape δ increased, the attenuation of the particle on shockwave intensity gradually reduced. These new findings hold significant theoretical implications for elucidating cavitation erosion mechanisms in liquid-solid two-phase flows and applications and prevention strategies in liquid-solid two-phase cavitation fields.

An Experimental Study of Cavitation Bubble Dynamics near a Complex Wall with a Continuous Triangular Arrangement

The mechanism of cavitation cleaning of complex surfaces has received more and more attention. In the present paper, with the help of a high-speed photography experimental system, the dynamic behavior of a cavitation bubble in symmetrical positions near a complex wall with a continuous triangular arrangement is investigated. In terms of the bubble size and the initial wall–bubble distance, the non-uniform shrinkage of the bubble collapse and the movement characteristics of the bubble centroid are revealed. The main conclusions are as follows: (1) The collapse dynamic behavior of the bubble near a complex wall with a continuous triangular arrangement can be divided into three typical cases. (2) According to a large number of experimental results under different parameters, the parameter ranges corresponding to the three cases and the critical values between different cases are given. (3) The larger the bubble size is, or the smaller the initial wall–bubble distance is, the more significant the effect of the complex wall is, and the greater the movement distance towards the complex wall during the collapse stage.