Azimuthal rotation induced by the Marangoni force makes small Leidenfrost droplets dance
説明
We observe zig-zag motions of small Leidenfrost water droplets (radii less than 0.6 mm) on a hot, flat substrate. To understand the motion, we conduct an experiment using a glass capillary to fix a droplet at its edge and to control the droplet height. Our thermographic and interferometric observations show that the droplets rotate both vertically and azimuthally. Based on results that the azimuthal rotation has a characteristic frequency depending on the substrate temperature and droplet height, we develop a semi-empirical model based on the unsteady Marangoni convection and its relaxation. We confirm that our model can predict the characteristic time of the zig-zag motion of unfixed droplets.
5 pages, 4 figures