Mixing of confined reacting co-axial jets with disparate viscosity

Mixing of miscible liquids with disparate viscosity is important in a number of industrial processes including reacting flows. When the reaction rate is much faster than the rate of mixing (Da >>1), the reaction becomes mixing limited. The relevant scale, Batchelor, for the reaction is much smaller than the turbulent dissipative scale for liquids (Sc ≈ 1000). Therefore, large-eddy simulation (LES) is the practical approach whereas DNS is inaccessible. However, subgrid-scale (SGS) modeling becomes challenging since there is large viscosity difference between the liquids and the mixture involves reacting fluids. In this study, we focus on mixing of two miscible liquids of different viscosity in a co-axial jet mixer. The experimental setup includes PIV and PLIF to resolve the velocity field and the mixture fraction. The computational approach is based on LES and the results with regular Smagorinsky, dynamic and dynamic mixed SGS models will be presented with comparison to experiments for the viscosity ratio of one. The experimental setup and the computational results for viscosity ratio of up to 1000; and the challenges in the SGS modeling of the reacting flows will be presented.