Nonlinear Stability in the Two-Fluid Model

The 1-D Two-Fluid Model (TFM) promises a powerful and computationally cheap platform for simulating multi-fluid flow phenomena. However, runaway Kelvin-Helmholtz instabilities plagued previous approaches, necessitating aphysical regularizations. We demonstrate a novel physics-based approach, using a simple turbulent viscosity model to provide nonlinear stabilization, compatible with inertial coupling. We develop a set of analytical and numerical tools to investigate the resulting dynamics, including turbulent cascades, chaos, and formation of churn or slug flow. Our approach opens up a wide range of new capabilities for the TFM by capturing the Kelvin-Helmholtz instability physically.