Theoretical and computational modeling of turbulence / interface interactions

The interaction between turbulence and surface tension is studied through direct numerical simulation of a canonical multiphase flow. An initially flat interface is inserted into a triply periodic box of decaying homogeneous isotropic turbulence, simulated for a variety of turbulent Reynolds and Weber numbers on mesh sizes of 512 and 1024. Unity density and viscosity ratios are used in order to isolate the interaction between fluid inertia and the surface tension force. The liquid volume fraction variance spectrum is used to study the spatial scales of corrugations on the interface. A case with zero surface tension is used as a reference, yielding a passive interface that moves materially with the fluid. In the presence of surface tension, the spectrum shows a distinct change in scaling that reflects a dramatic decrease in interface corrugations for length scales smaller than the Kolmogorov critical radius/Hinze scale. Probability density functions of the maximum principal curvature demonstrate near collapse of the data to a single curve when normalized by this length scale. The governing equations are filtered to perform a priori testing of sub-grid scale models and to highlight the role of surface tension in the cascade of liquid volume fraction variance from large to small scales.