An Experimental Investigation of a Wind-Driven Water Droplet over the Slippery Liquid Infused Porous Surface

The promising anti-icing performance of the slippery liquid infused porous surface (SLIPS) has been recently demonstrated for various engineering applications. The runback icing for aircraft and wind turbines could be effectively mitigated considering the timely removal of water droplet by the wind shearing force due to the low adhesion on the SLIPS. In this study, the flow field both inside and around the wind-driven droplet over the SLIPS was experimentally investigated by using Particle Image Velocimetry (PIV) technique. Previous studies majorly focus on the internal flow pattern before the droplet incipient motion. In this study, the flow field inside a moving droplet was firstly investigated. As a result of the low surface adhesion of the SLIPS, droplet oscillations were eliminated and the droplet internal flow field could be corrected from the optical distortion. Besides the discussion on the wind speed, the droplet viscosity was also studied by varying the water concentration of the glycerin-water solution. It was found that the internal circulation was highly related with the droplet viscosity. The inner circulations within the water droplet would be reduced, or eliminated, when the droplet viscosity was increased, which would change the droplet motion from sliding into rolling. It was suggested that the internal flow should be considered when theoretically modeling the wind-driven droplet movement over the SLIPS. This study could provide experimental evidence for a broader application of the SLIPS in the icing-related industrial world.