Experimental Study on the Dynamic Droplet Impingement Force on Surfaces with Various Wettability at High Weber Number

Understanding the fundamental of the durability degradation of water/ice-phobic coatings is crucial to the development of the novel anti-/de-icing technology. In the present study, an experimental investigation was conducted to evaluate the dynamic water droplet impact force on surfaces with different wettability at high Weber numbers. Three surfaces (i.e., Hydrophilic, Hydrophobic, and Super Hydrophobic surfaces) were utilized as the substrate during the impingement process of the water droplet at both room temperature and supercooled level. The impact force is measured by a piezoelectric impact force sensor synchronized with a high-speed image technique to characterize the dynamic collision force as well as the dynamic impingement morphology. The result shows that, at the kinematic stage, the force for impingement experiences a sharp increase which is followed by the self-similar prediction when the droplet is compressed to a truncated sphere. The dynamic impact force would drive away from the theoretical prediction when the spreading stage began and reach the maximum as the self-similar high-pressure region propagates to the apex of the droplet. Then, it is followed by long-time decay to zero before the receding stage. While the impingement morphology varies significantly with different surface hydrophobicity, the variation of impact force at different surfaces maintains within the small range. It shows a limited effect of dynamic impact force on the various wettability. The findings derived from the present study are very helpful in understanding the fundamental water erosion effect, which can be beneficial to the development of a more durable water/ice repellence coating.