A numerical study of gravity-driven instability in strongly coupled dusty plasma. Part 2: Hetero-interactions between a rising bubble and a falling droplet

TL;DR

This study numerically investigates the complex hetero-interactions between rising bubbles and falling droplets in a strongly coupled dusty plasma, revealing how their dynamics depend on arrangement, coupling strength, and initial positioning.

Contribution

It extends previous work by analyzing combined bubble-drop interactions in different configurations within a strongly coupled dusty plasma using 2D numerical simulations.

Findings

Interaction dynamics are governed by vortex pairing and gravity-induced vertical motion.

Horizontal separation speed decreases with increasing coupling strength.

Arrangement and initial positioning significantly influence the interaction outcomes.

Abstract

In part I (arXiv:2006.12393) (accepted in JPP), we simulated individual dynamics of a rising bubble and a falling droplet in an incompressible limit of a strongly coupled dusty plasma (SCDP) using a generalized hydrodynamic viscoelastic fluid model. In interest to understand hetero- (bubble-drop) interactions between them, we extend this study to their combined evolution through two arrangements: First, both are placed side-by-side in a row at the same height. We observe that the overall dynamic governs by the competition between the rotational motion induces due to the pairing between two co-rotating inner vorticity lobes and net vertical motion of two dipolar-vorticities (upward for bubble and downward for droplet) induces due to the gravity. In second arrangement where the vertically aligned bubble (below) and droplet (above) after collision exchange their blobs/lobes and subsequently start to move horizontally in opposite directions away from each other. This horizontal movement gets slower with increasing coupling strength. For the these arrangement, we consider the varying distance between the fixed-size bubble and droplet, and varying coupling strength which represents the nature of our medium. A series of 2D numerical simulations have been conducted to visualize these interactions