Shape Oscillation And Near-wall Collapsion Of Microbubbles In Ultrasound Field

Because of its special physical properties,microbubbles have been widely used in contrast-enhanced ultrasound,gene therapy,water treatment and other fields.Especially in the medical industry,targeted microbubble destruction technology is considered to be one of the most promising medical methods.Therefore,it is necessary to make a thorough theoretical analysis of its response characteristics in the ultrasound field.In this paper,the shape oscillation and near-wall collapsion characteristics of microbubbles in ultrasound field are studied in detail,which are mainly divided into two parts: the shape oscillation characteristics of microbubbles and the collapsion characteristics of near-wall microbubbles.CFD computational fluid dynamics(CFD)method is used in both parts.Based on the FLUENT platform,VOF model and self-defined external ultrasound field are used in the study.In the part of shape oscillation,the mode distribution of bubble shape oscillation and the fourth-order mode flow field are analyzed,and the feasibility of the model is verified.The results are consistent with the previous experimental results.The analysis of flow field shows that the oscillation mode caused by bubble surface instability is the combination of liquid viscosity,bubble diameter and ultrasound field.The maximum temperature,maximum velocity and collapse time of microbubbles with different initial radius near the wall were analyzed under different ultrasound frequencies and driving pressures.The physical characteristics of primary collapsion and secondary collapsion were also analyzed.The effect of secondary collapse on the wall is greater than that of primary collapse,which further reveals the collapsion mechanism of near-wall microbubbles in the ultrasound field.