Effect of liquid viscosity and surface tension on mass separation of shear-driven liquid film at a sharp corner

Abstract

Formation of a thin liquid film along a wall that is driven by an adjacent high velocity gas has many applications such as liquid atomizers, fuel film transport in internal combustion engines, and refrigerant systems. At a geometric singularity like a sharp corner, the liquid film may remain attached to the wall or become separated depending on gas-liquid flow conditions. Mean film layer inertia and instabilities, which form large amplitude waves at liquid film interface are two mechanisms for the separation of shear-driven films from a sharp corner. Inertial force due to the mean film layer and the interface layer which includes large amplitude waves both influence the liquid mass separation at the corner. In this study, the effect of liquid film properties such as viscosity and surface tension on these processes and ultimately the liquid mass separation of the shear-driven liquid film from a sharp corner was investigated. Experimental results revealed that as liquid film viscosity decreased, more mass became separated from the sharp corner due to an increase in both large amplitude wave amplitudes and mean film layer inertial force. This study also showed that although liquids with smaller surface tension developed a thiner mean film layer and less large amplitude waves at the interface, the resultant high force imbalance between the destabilizing inertial force and surface tension restoring force led to a higher liquid mass separation at the sharp corner.