Molecular shear heating and vortex dynamics in thermostatted two-dimensional Yukawa liquids

TL;DR

This study uses molecular dynamics simulations to investigate vortex dynamics and molecular shear heating in strongly coupled Yukawa liquids under shear flow, demonstrating effective thermostating methods that preserve large-scale vortex behavior.

Contribution

It introduces a novel configurational thermostat to efficiently remove microscale heat in MD simulations of Yukawa liquids without affecting vortex dynamics.

Findings

Molecular shear heating reduces coupling strength exponentially.

Configurational thermostat effectively removes heat while preserving vortex structures.

Comparison shows differences in shear flow evolution with and without molecular heating.

Abstract

It is well known that two-dimensional macroscale shear flows are susceptible to instabilities leading to macroscale vortical structures. The linear and nonlinear fate of such a macroscale flow in a strongly coupled medium is a fundamental problem. A popular example of a strongly coupled medium is a dusty plasma, often modelled as a Yukawa liquid. Recently, laboratory experiments and MD studies of shear flows in strongly coupled Yukawa liquids, indicated occurrence of strong molecular shear heating, which is found to reduce the coupling strength exponentially leading to destruction of macroscale vorticity. To understand the vortex dynamics of strongly coupled molecular fluids undergoing macroscale shear flows and molecular shear heating, MD simulation has been performed, which allows the macroscopic vortex dynamics to evolve while at the same time, "removes" the microscopically generated heat without using the velocity degrees of freedom. We demonstrate that by using a configurational thermostat in a novel way, the microscale heat generated by shear flow can be thermostatted out efficiently without compromising the large scale vortex dynamics. In present work, using MD simulations, a comparative study of shear flow evolution in Yukawa liquids in presence and absence of molecular or microscopic heating is presented for a prototype shear flow namely, Kolmogorov flow.