Simulation of turbulent mixing of confined co-axial jets with disparate viscosity*

Viscosity variations have shown to affect the mixing behavior and chemical yield in industrial processes. This study investigates the mixing of two miscible liquids of different viscosity in a co-axial jet mixer. The computational approach is based on large-eddy simulation (LES) using the opensource software OpenFOAM. The computational domain is decomposed with a structured grid and optimized for parallel performance. Theoretical turbulent flow profile is imposed at the inlet boundary.  Three different LES sub-grid scale (SGS) models, namely the regular Smagorinsky (SM), dynamic (DM) and dynamic mixed (DMM) models have been compared.  It appears that at moderate Reynolds number considered here, both DM and DMM results compare well with experiments at viscosity ratio of one. The time-averaged mixture fractions, velocity, and RMS values for mixing fluids with uniform viscosity are compared with literature and experimental data.  The numerical results for viscosity ratios from 1 to 1000 will be discussed.