Quantitative analysis of particle behavior constituting multiple coherent structures in liquid bridges

Hypothesis

Coherent structures by low-Stokes-number particles are induced within a closed flow, in which ordered flow regions known as Kolmogorov-Arnold-Moser (KAM) tori emerge. A variety of structures with different spatial characteristics has been predicted by varying the Stokes number, whereas the coexistence of structures in flow suspending various types of particles has not been hitherto demonstrated.

Experiments

Half-zone liquid bridges of $O$ (

) are prepared as a closed system to induce thermocapillary-driven time-dependent flow under normal gravity conditions. By suspending single or multiple types of particles of $O$ (

) in diameter, we track the particle trajectories with two synchronized high-speed cameras and count the particles forming coherent structures.

Findings

The coexistence of various coherent structures is unveiled in systems where particle groups of different diameters are simultaneously suspended. We demonstrate the constitution of multiple coherent structures in the reference frame rotating with traveling wave: Some structures are dominated by a single type of particles, whereas some others are composed by various type of particles. Through a quantitative evaluation of the number of particles forming each manifested coherent structure, “the attractivity” of structures is discussed.