An improved three-dimensional lattice Boltzmann-volume of fluid (LB-VOF) method for simulation of laminar liquid jet breakup with high density ratio

Abstract

Lattice Boltzmann method (LBM) has been widely developed in the past decade, while most of the previously presented LBMs are confined to two-phase problems with a low-density ratio. In the present study, we developed the free surface model based on the volume of fluid (VOF) method to a three-dimensional two-phase LBM (LBM-VOF) and utilized this new model to simulate the breakup of a water jet in the air. This problem is characterized by high density and viscosity ratios with the values of about 830 and 58, respectively. Numerical codes are implemented in the open-source library of parallel Lattice Boltzmann solver (PALABOS), and the results are compared and validated against experimental and published numerical outcomes. It is shown this new model could properly confine spurious currents. Afterward, the LBM-VOF model is used to simulate different water jet regimes, including periodic dripping, dripping faucet, and jetting regimes. Furthermore, the dynamics of fluid jet formation and droplet breakup are comprehensively discussed in different ranges of the Weber number (0.063 < We < 6) and three nozzles with different sizes. Results show that the proposed LBM-VOF model is capable of simulating all the three mentioned regimes and their specific characteristics. The proposed model accurately predicts the ranges of critical Weber number (2.4 < We < 2.84) at which the regime transition from periodic dripping to jetting occurs; which is in agreement with the theoretical relation. Moreover, when the dripping to jetting transition occurs, the length of breakup and the frequency of droplet production increased sharply by approximately 3.6 and 3, respectively, while the volume of produced droplets decreased by about 2.4.