Liquid Drop Breakup in Turbulent Flow

Abstract

The focus of this study is to gain a fundamental understanding of liquid-liquid dispersion formation in homogeneous isotropic turbulence. This information is crucial to improve the reliability of existing models that describe drop breakup in turbulent flow. These models inherit numerous assumptions, simplifications, experimental constants and fitting parameters. Visualization and quantification of drop behavior in homogeneous turbulence will allow assessment of these models. Direct numerical simulations were used to investigate the dynamics of drop behavior. The free energy lattice Boltzmann method was used to perform simulations. The homogeneous isotropic turbulence was generated in a three-dimensional fully-periodic domain of 300300300 lattice units in size using a forcing method. Three turbulent flow fields at different levels of energy input were investigated. Then, drops of different initial diameter were injected. The dispersed to continuous fluid viscosity ratios equal to 0.1, 1, and 10 were considered. The DNSs produce detailed description of the flow. The main goal of this study was to translate these data to the useful quantities that can be applied to assess the drop breakup models. This work specifically focused on understanding of drop interaction with turbulent structures. A normalized Qn criterion was used to visualize the structures. Different combinations of a threshold value and a cutoff volume were studied to explore the effect of these two important parameters and to identify the best combination. The interaction between turbulent vortices and the drops was visualized by extracting coherent structures and tracking liquid-liquid interface in two phase turbulence. The three-dimensional energy spectra of single phase and two-phase turbulence were also quantified. The statistical characteristics of liquid-liquid turbulence were investigated: the probability density function of vorticity, of normalized energy dissipation rate, and the eigenvalues of the strain tensor. By utilizing these tools, the guidelines are proposed for improvement of the breakup models.