Coherent Particle Structures in High-Prandtl-Number Liquid Bridges

Abstract

Clustering of small rigid spherical particles into particle accumulation structures (PAS) is studied numerically for a high-Prandtl-number (Pr = 68) thermocapillary liquid bridge. The one-way-coupling approach is used for calculation of the particle motion, modeling PAS as an attractor for a single particle. The attractor is created by dissipative forces acting on the particle near the boundary due to the finite size of the particle. These forces can dramatically deflect the particle trajectory from a fluid pathline and transfer it to certain tubular flow structures, called Kolmogorov–Arnold–Moser (KAM) tori, in which the particle is focused and from which it might not escape anymore. The transfer of particles can take place if a KAM torus, which is a property of the flow without particles, enters the narrow boundary layer on the flow boundaries in which the particle experiences extra forces. Since the PAS obtained in this system depends mainly on the finite particle size, it can be classified as a finite-size coherent structure (FSCS).

Finite-size coherent particle structures in high-Prandtl-number liquid bridges

“…The same accumulation measure has already been used in numerical and experimental studies [50,66]. For convenience we select the number of cells N = 4000 equal to the number of particles, thus N = N/N cells = 1, and use 10 × 40 × 10 cells in the radial, azimuthal, and axial directions, respectively.…”

“…While PAS has been studied extensively in lowand moderate-Prandtl-number liquid bridges on the ground, comprehensive experimental data and numerical results for Pr = 68, which is foreseen for JEREMI, are still lacking. Merely, a few hints about the existence of PAS in Pr = 68 thermocapillary liquid bridges have been detected during ISS experiments [49], while recent numerical studies [50,51] reported some preliminary findings on PAS formation. In the present study, we investigate PAS in thermocapillary liquid bridges for Pr = 68 to provide a numerical basis for future space experiments as well as to identify flow parameters and particle sizes for which PAS and FSCS are expected under zero gravity.…”