The Effect of Impact Angle on the Secondary Droplets at High Impact Velocity
This study focuses on the secondary droplets ejected during splashing at different impact angles. We consider the theory of Riboux & Gordillo , which attributes the generation of secondary droplets to a lift force that acts on the spreading lamella, and propose a new approach to handle the oblique impact. This approach is based on previous studies on the lamella formed by impinging jets, where the impacting flow is distributed in the azimuthal direction. To validate the proposed method, we used a flywheel experiment and captured the secondary droplets that are ejected at Weber number larger than 4500 at three different impact angles. In our experimental setup, the droplets were formed by a droplet generator and then let to fall freely due to gravity until impacting the substrate, which was mounted on a flywheel. The small and fast secondary droplets were captured using a shadowgraph technique together with a high-resolution camera and Nd:YAG laser with diffuser optics. The experimental results showed an acceptable agreement with the prediction made by our method in all studied cases. We demonstrate that the shape and droplet size distribution are affected by the impact angle, while the velocity of the ejected droplets remains constant in the azimuthal direction.