Coherent structures of Formula Presented by low-Stokes-number particles suspended in a half-zone liquid bridge of high aspect ratio: Microgravity and terrestrial experiments

We investigate the coherent structures by low-Stokes-number particles suspended in half-zone liquid bridges of high Prandtl number via microgravity and terrestrial experiments. We especially focus on the structure by the suspended particle accumulation, or, the particle accumulation structure (PAS), of Formula Presented in azimuthal wave number emerged in the traveling-wave-type time-dependent “oscillatory” convection. The particles form the closed path with a spiral structure in tall or high-aspect-ratio liquid bridges under both micro- and normal gravity conditions. Their formation process is evaluated by applying the accumulation measure, and it is indicated that the formation time of the structure is of the order of a thermal diffusion time regardless of the difference of Prandtl number as well as the gravitational acceleration. The spatial correlation between the coherent structure and the thermal wave over the free surface is illustrated in the rotating frame of reference. By the terrestrial experiments, we indicate how the PAS is conformed by the individual particle motions in the laboratory frame and the rotating frame of reference via two-dimensional particle tracking. We also indicate their occurring condition as a function of the slenderness of the liquid bridges in terms of the volume ratio, and we evaluate the morphological characteristics of the spiral structure.