Investigating the effects of viscosity and density ratio on the numerical analysis of Rayleigh-Taylor instability in two-phase flow using Lattice Boltzmann method: From early stage to equilibrium state.

• The LBM is used to investigate the complete behavior of RTI numerical model. • Good agreements with experiment and other numerical studies are obtained. • Instability rate is found to be greatly affected by Atwood numbers. • The equilibrium state of the instability is successfully simulated. The gravitational liquid-liquid two-phase flow was numerically investigated by using lattice Boltzmann method (LBM). The method was implemented for analyzing a model of Rayleigh-Taylor Instability (RTI). The feasibility of this present numerical approach was investigated by performing convergence test, and validating the obtained results with those obtained from experiments as well as other preceding numerical methods. Qualitative and quantitative comparisons were examined, whereby good agreements are noted for all cases. Parametric studies were also conducted by varying both of Reynolds and Atwood numbers to investigate the effects of viscosity and density ratio on the behavior of fluids interaction. Based on the obtained outcomes of this numerical approach, the present LBM was able to successfully simulate the complete phenomena during RTI, i.e.: the linear growth, secondary instability, bubble rising and coalescence, and liquid break-up, including turbulent mixing conditions as well as the equilibrium state. The finding obtained from this work might be beneficial in the investigation of parametric behavior in design of processes equipment such as for separator design. [ABSTRACT FROM AUTHOR]