Vision based cone angle estimation of bubbly cavitating flow and analysis of scattered bubbles using micro imaging techniques

Hydrodynamic cavitation is an effective and alternative treatment method in various biomedical applications such as kidney stone erosion, ablation of benign prostatic hyperplasia tissues and annihilation of detrimental cells. In order to effectively position the orifice of bubbly cavitating flow generator towards the target and control the destructive cavitation effect, cone angle of multi-phase bubbly flow and distributions of scattered bubble swarms around main flow must be determined. This paper presents two vision based solutions to determine these quantities. 3D Gaussian modeling of multi-phase flow and edge slopes of cross-section are used to estimate the cone angle in a Kalman filter framework. Scattered bubble swarm distributions around main flow were assumed as a normal distribution and analyzed with the help of covariance matrix of the bubble position data. Hydrodynamical cavitating bubbles were generated from 0.45 cm long micro probe with 152μm inner diameter under 10 to 120 bars pressures and monitored via Particle Shadow Sizing technique. Proposed methods enabled to quantize the increasing inlet pressure effect on bubbly cavitating multi-phase flow.

I. Introduction

Sudden pressure drop down below the vapor pressure of the liquid results in vaporization and bubble generation. This phenomenon is called hydrodynamic cavitation. Generated bubbles in lower inlet pressure, may collapse when they are subjected to atmospheric pressure. Highly destructive shock waves are generated by the collapse of cavitation-caused bubbles. Continuous collision of solid surfaces and generated bubbles leads to cavitation erosion.