Molecular dynamics simulations of the distance between the cavitation bubble and benzamide wall impacting collapse characteristics

Abstract

The cavitation process has become a promising wastewater treatment technology. The use of bubble collapse can effectively degrade the benzamide in wastewater. However, the mechanisms of bubble collapse and pollutant wall cannot be explained accurately. In this study, models with different distances (d) from the cavitation bubble to the benzamide wall are established to understand the relationship between the distance from the cavitation bubble to the wall and the collapse characteristics. The TIP4P-FB water model and the ReaxFF are selected to study the dynamic characteristics and pressure field variation rule of bubble collapse, and compares it with R–P equation derivation. The results show that the bubble in the middle of the parallel walls has the largest change rate of the volume during the initial stage of the collapse. In the acceleration stage, the closer the bubble is to the wall, the higher the change rate of the bubble volume is. The longer the time in the maximum pressure field is, the greater the maximum pressure is. The shape of the bubble far from the wall is relatively smooth, and the spherical bubble gradually develops into an irregular ellipsoid shape. When d < 1.59 R0, the wall is in the maximum pressure field released through bubble collapse. The change rate of the volume and the change of the maximum releasing pressure in the simulation are consistent with the rule of the derivation of the R–P equation. The simulation results are fully verified.