Viscoelastic effects on asymmetric two‐dimensional vortex patterns in a strongly coupled dusty plasma

Abstract

Strongly coupled dusty plasma medium is often described as a viscoelastic fluid that retains its memory. In a flowing dusty plasma medium, vortices of different sizes appear when the flow does not remain laminar. The vortices also merge to transfer energy between different scales. In the present work, we study the effect of viscoelasticity and compressibility over a localized vortex structure and multiple rotational vortices in a strongly coupled viscoelastic dusty plasma medium. In case of single rotating vortex flow, a transverse wave is generated from the localized vortex source and the evolution time of generated waves is found to be reduced due to finite viscoelasticity and compressibility of the medium. It is found that the viscoelasticity suppresses the dispersion of vorticity. In the presence of multiple vortices, we find, the vortex mergers get highly affected in the presence of memory effect of the fluid, and thus the dynamics of the medium gets completely altered compared to a non‐viscoelastic fluid. For a compressible fluid, viscoelasticity dampens the energy in the sonic waves generated in the medium. Thus a highly viscoelastic and compressible fluid, in some cases, behaves similarly to an incompressible viscoelastic fluid. The wave‐front like rings propagate in elliptical orbits keeping the footprint of the earlier position of the point‐vortex. The rings collide with each other even within the patch vortex region forming regions of high vorticity at the point of intersection and pass through each other.

Evolution of charged grains in harmonic force field

“…In the past few decades, dusty plasmas have attracted much research attention because they play important roles in many phenomena in the astrophysical environments, the Earth's ionosphere, 2–7 as well as in industrial processes such as semiconductor device manufacturing, plasma etching, materials coating and modification, etc 1,6–9 . As a result, there has been much interest in the theory and applications of dusty plasmas, covering a large range of the physical parameters involved 10–35 . Since the electrons have much higher mobility, inelastic collisions between the electrons and dust grains are much more frequent than that of ions, so that the dust grains are usually highly negatively charged 10 …”

“…Song et al 22 studied the effect of the plasma temperature on the structures and the dynamics of dust clusters, and found that depending on the discharge power, dust clusters can also be in crystal or liquid states. Existing studies have also considered various internal and external, such as ion and neutral‐particle drag, thermophoretic, radiation pressure, gravitational, etc., forces and other effects on the dynamics and structure of dust grains in a plasma 11–35 …”