Department Seminar of Ilya Barmak

School of Mechanical Engineering Seminar
Wednesday, December 1, 2021 at 14:00
Wolfson Building of Mechanical Engineering, Room 206

COHERENT PARTICLE STRUCTURES IN THERMOCAPILLARY LIQUID BRIDGES

Dr. Ilya Barmak

School of Mechanical Engineering, Tel Aviv University, Tel Aviv 69978, Israel

In this talk, I will discuss the transport of liquid and of small rigid spherical particles in thermocapillary liquid bridge under zero-gravity conditions. When dispersed in the flow, small rigid particles of a dilute suspension are found to cluster into closed threads, called particle accumulation structures (PAS). The segregation of multiple particles into PAS is modeled in the framework of a one-way coupling as an attraction of a single non-interacting particle to an attractor in or near Kolmogorov-Arnold-Moser (KAM) tori of the unperturbed fluid flow (without particles). We employ highly-resolved numerical simulations to compute the flow fields of the liquid of high Prandtl number of 68 at supercritical thermocapillary Reynolds numbers, when the flow arises as an azimuthally traveling hydrothermal wave. The Langrangian transport of fluid elements reveals the coexistence of regular and chaotic streamlines in the frame of reference rotating with the hydrothermal wave. A regular streamline winds on a closed streamtube which corresponds to KAM torus. The intricate KAM structures of the flow are found to have their counterpart in a multitude of different attractors for the particle motion.

I will present some examples of particle accumulation structures and discuss the dependence of PAS on particle size, particle-to-fluid density, and Reynolds number. We have conducted a large parametric study that reveals the most probable combinations of particle size and density ratio which can lead to particle clustering in the joint Japan European Research Experiment on Marangoni Instability (JEREMI) planned to be carried out on the International Space Station (ISS).

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