Droplet impact on pools with base topography*

Our recent work has shown that pool depth can significantly influence outcomes when droplets impact shallow pools, which is relevant to important processes such as raindrop impact, icing, and crop spraying. Here we consider the case where the pool base is not flat, but instead has a topography that breaks the axisymmetry of traditional normal droplet impact onto a static pool. In particular, we focus on configurations with linearly varying and abruptly changing pool depths, such as a submerged step. These ostensibly small modifications to the traditional setup can have a dramatic effect post-impact, generating inherently three-dimensional dynamics and influencing both the number and direction of ejected satellite droplets. Besides quantifying the resulting asymmetric behavior, we establish the limits within which base topography affects impact outcomes, in terms of both pool depth and impact position, for use in applications.