In fluid physics, there’s often a tug of war between different effects. For droplets falling onto a surface colder than their freezing point, the hydrodynamics of impact, sudden heat transfer, and solidification processes all compete to determine how quickly and in what form droplets freeze.
The images above form a series based on changing the height from which the droplet falls. Each image is divided into two synchronized parts. On the left, we see a visible light, top-down view of the freezing droplet; on the right, we see an infrared view of freezing. As the height of impact increases, the shape of the frozen drop becomes more elaborate, moving from a flat splat with a small conical tip all the way to one with a concentric double-ring in its center. (Image and research credit: M. Hu et al.)