چكيده به لاتين
Analysis and simulation of droplet formation and jet breakup is a complex problem with many applications in various engineering fields such as inkjet printing, spray, solar cell production and food processing. Numerical methods should be able to accurately simulate this physics as well as predict different jet flow regimes. One of these methods is the Lattice Boltzmann method (LBM), which has been widely developed in the last decade. The Lattice Boltzmann method is a computational fluid dynamics method for simulating fluid flow, using the Boltzmann equation instead of solving the Navier-Stokes equations. This method has several advantages over other computational fluid dynamics methods, especially in dealing with complex boundaries and multiphase environments, and it provides the possibility of simulating and performing calculations in parallel. In many cases, the studied fluids usually have a high density ratio and viscosity ratio. However, due to the instability and production of high spurious velocities in high range of density and viscosity ratios, many two-phase and multi-phase models in the Lattice Boltzmann method are not able to simulate multiphase flows. In present study, a two-phase three-dimensional Lattice Boltzmann method based on fluid volume (LBM-VOF) has been developed and used to simulate the formation of a water jet in air, which the high density and viscosity ratios are about 830 and 60, respectively. Also, the numerical codes are implemented in the open source library of parallel Lattice Boltzmann solver (PALABOS) and the obtained results are compared and validated with experimental and published numerical results. It has been shown that the present new model can correctly limit the spurious velocities, reducing the virtual velocities at the fluid interface by about 20 times, compared to multiphase models such as Shan and Chen. After that, the LBM-VOF model is used to simulate different water jet regimes, including periodic dripping, dripping faucet and jet regimes. In addition, the dynamics of fluid jet breakup and droplet formation are comprehensively discussed in different ranges of Weber number (0.063 < We < 6) and three nozzles with different sizes. The results show that the proposed LBM-VOF model is capable of simulating all three mentioned regimes and their special features.
