Experimental and Numerical Study of Droplet Impact on Radially Flowing Liquid Film

In this paper, a single droplet impact onto a radially flowing liquid film is investigated both experimentally and numerically. The interfacial evolution and dynamic features are studied in detail with regard to various droplet impact velocities and film flow rates. Also, the corresponding mechanisms are analyzed with the aid of numerical results using the coupled level set and volume of fluid method. Results show that the droplet impact on the radial film produces a larger crown radius in the direction perpendicular to the film flow compared with the unidirectional film. Increasing the impact velocity leads to increases in crown height and upstream radius, but it has a weak effect on the downstream radius. As for the effect of the film flow rate, its increase causes a rise in the secondary droplet number in the upstream but makes the finger jets associated with the crown splashing less developed. Besides, increasing the flow rate of the liquid film results in increases in the upstream crown height and downstream radius but decreases in the downstream crown height and upstream radius. Finally, a formula for predicting the threshold of splashing is built up based on the film flow Reynolds number and the droplet Weber number.