Two-Scale Large Eddy Simulation Method for Incompressible Two-Fluid Turbulent Flows

Accurate simulation capabilities for incompressible highly variable density turbulent (IHVDT) flows are critically important for many natural and engineering applications. Developing a large eddy simulation (LES) capability that incorporates all of the relevant subgrid-scale effects is an urgent, currently unmet, scientific and technical challenge. We propose a two-scale framework using the volume-of-fluid method to simulate the incompressible, two-fluid LES problem. This two-scale framework closes the unresolved fluxes in the interface evolution equation through a combination of Lagrangian particles and fractal interpolation techniques, resulting in a mixed Eulerian-Lagrangian methodology. Our objective is to provide physically accurate surface statistics for the resolved flow, predictions of the unresolved bubble/drop statistics up to the Hinze scale, and to conserve volume for each phase. As a canonical problem, we consider the breakup of a finite-thickness sheet of immiscible fluid immersed in forced homogeneous isotropic turbulence. Using direct numerical simulation, a priori analysis, and a posteriori tests using traditional LES, we point out that neglecting the interface closure terms leads to an under-prediction of the resolved surface statistics during interface breakup as well as the resulting drop/bubble distribution at later stages. We will present analysis and testing of the proposed two-scale LES method to establish the validity and efficacy of the new framework.