A Volume-of-Fluid Dual-Scale Approach for Simulating Turbulent Liquid/Gas Interactions

Advances to a dual-scale modeling approach (Gorokhovski and Herrmann, 2008) are presented to describe turbulent phase interface dynamics in a Large Eddy Simulation spatial filtering context. Spatial filtering of the governing equations to decrease the burden of Direct Numerical Simulation introduces several sub-filter terms that require modeling. Instead of developing individual closure models for the interface associated terms, the dual-scale approach uses an exact closure by explicitly filtering a fully resolved realization of the phase interface. This resolved realization is maintained on a high-resolution over-set mesh using a Refined Local Surface Grid approach (Herrmann, 2008) employing an un-split, geometric, bounded, and conservative Volume-of-Fluid method (Owkes and Desjardins, 2014). Advection of the phase interface on this DNS scale requires a reconstruction of the fully resolved interface velocity. This velocity is the sum of the filter scale velocities, readily available from an LES solver, and sub-filter velocity fluctuations. These fluctuations can be due to sub-filter turbulent eddies, which can be reconstructed on-the-fly using a local fractal interpolation technique (Scotti and Meneveau, 1999) to generate time evolving sub-filter velocity fluctuations. In this work, results from the dual-scale LES model are compared to DNS results for four different realizations of a unit density and viscosity contrast interface in a homogeneous isotropic turbulent flow at infinite Weber number. Introduction of a sub-filter turbulent velocity reconstruction in a passive scalar context is the first step towards use of a dual-scale model for multiphase applications.