Evaluation of existence region and formation time of particle accumulation structure (PAS) in half-zone liquid bridge

We focused on the particle accumulation structure (PAS) produced by the thermocapillary effect in a half-zone liquid bridge. Although models of the formation of the PAS have been previously proposed, they have not been experimentally verified. An assessment of the region in which the PAS exists is very subjective and often dependent on the observer, and this has necessitated the development of an objective and quantitative evaluation method. We therefore conducted a series of experiments to verify the physical model of the particle path lines in a rotating frame of reference using the fundamental frequency of the hydrothermal wave. We evaluated the intensity of the particle accumulation based on a modification of the "accumulation measure" proposed by Kuhlmann and Muldoon (Phys. Rev. E, 2012) to objectively and quantitatively determine the existence region of the SL-1 PAS. The results of the quantitative experiment revealed that the best aspect ratio (ratio of the height to radius) of the liquid bridge for the SL-1 PAS was about 0.64, and that the PAS formation time was nearly the same as the thermal diffusion time under the considered conditions (184 words, within 200 words).