Session: 04-02 Cavitation and Bubbly Flows

Paper Number: 86006

86006 - Study on the Entrainment Behaviors of the Droplet Jet Between Plates Considering the Hydrophobicity of the Plate 

The liquid jet produced by flow focusing is applied in the fields of needle-free injection, inkjet printing, and so on. A concave interface of the liquid forms a high-speed jet when the impulsive acceleration acts on since the liquid momentum converges to the center of curvature of the interface. Interestingly, we find that the jet also is induced when the impulsive acceleration acts on the convex interface. In the present study, the mechanism and evolution of the liquid jet formed from a convex interface are analyzed by combining experimental observation and numerical simulation. In the experiment, A narrow gap of 0.8-mm depth is produced using two parallel acrylic glass plates. The glass plates are treated with a superhydrophobic coating to form a convex liquid interface. We inject water into the narrow gap, and a circle droplet of 12-mm diameter is shown in the front view while the side view shows a convex interface protruding from the liquid to the air. Subsequently, a pulsed laser is focused at the center of the droplet through a convex lens to generate a pulsed bubble to accelerate the movement of the convex interface. The development process of the liquid jet is observed by high-speed photography. A numerical simulation is conducted based on the two-phase compressible solver compressibleInterFoam in the open-source framework of OpenFOAM. The volume of fluid(VOF) method and large eddy simulation (LES) turbulence model are used to capture the gas-liquid interface and small-scale flow structures, respectively. The experimental observation shows that a liquid jet is produced from each side of the convex interface, respectively, compared with that generated at the center of the concave interface. The walls of the glass plates are viewed as mirrors and thus, the momentum of the fluid converges at the center of the curvature of the interface, i.e., the positions of the glass plate walls. With the development of the liquid jet, an entrainment phenomenon is observed on the walls. The results of the numerical simulation show that the entrainment phenomenon is induced by the shear force between gas and liquid. Finally, we discuss the influence of different contact angles on the jet velocity, concluding that the jet velocity decreases as the contact angles increase.

Presenting Author: GuangHang Wang University of Chinese Academy of Sciences；Institute of Mechanics, Chinese Academy of Sciences