Numerical investigation of the effect of different parameters on emitted shockwave from bubble collapse in a nozzle

Cavitation can be extremely beneficial for the first spray breakup and to enhance atomization quality. An Eulerian/Lagrangian approach using Reynolds average Navier-Stokes (RANS) and bubble dynamic equations was used for the prediction of cavitation inception. A comprehensive validation was also performed using the Eulerian and Lagrangian equations in the current numerical approach. First, the carrying liquid was simulated by the finite volume method in order to obtain pressure and velocity in the whole computational domain, and a one-way coupling between the Eulerian and Lagrangian parts was used. The Reynolds stress transport model (RSTM) was used for calculating turbulent parameters, and the continuous filter white noise (CFWN) model was used for modeling fluctuating terms of velocity. Rayleigh-Plesset and a modified form of the bubble motion equation were also applied to study the bubble dynamic and bubble position inside the nozzle. A modified form of critical pressure was also used to evaluate critical pressure as cavitation starts and showed critical pressure increases significantly as cavitation starts. The bubble shock wave due to the first and second bubble collapse was predicted in the cavitating and non-cavitating flow. A shock wave due to the bubble’s first collapse in cavitation inception conditions increased to ۲۸ Mpa. Results showed that increasing the pressure difference can severely increase the shockwave while increasing the initial radius will decrease the amount of the emitted shockwave. Effects of surface tension, dynamic viscosity, and liquid density on bubble dynamic were evaluated.

Keywords:

Cavitation , Shockwave , Eulerian/Lagrangian approach , Nozzle