Molecular shear heating and vortex dynamics in thermostatted two dimensional Yukawa liquids
Abstract
It is well known that twodimensional 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 molecular dynamics (MD) studies of shear flows in strongly coupled Yukawa liquids indicated the occurrence of strong molecular shear heating, which is found to reduce the coupling strength exponentially leading to the 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 the present work, using MD simulations, a comparative study of shear flow evolution in Yukawa liquids in the presence and absence of molecular or microscopicmore »
 Authors:
 Institute for Plasma Research, HBNI, Bhat Gandhinagar, Gujarat 382 428 (India)
 Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India)
 Publication Date:
 OSTI Identifier:
 22600034
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Physics of Plasmas; Journal Volume: 23; Journal Issue: 7; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; COMPUTERIZED SIMULATION; DEGREES OF FREEDOM; FOKKERPLANCK EQUATION; HEAT; HEATING; INSTABILITY; LIQUIDS; MOLECULAR DYNAMICS METHOD; NONLINEAR PROBLEMS; PLASMA; SHEAR; THERMOSTATS; TWODIMENSIONAL CALCULATIONS; VELOCITY; VORTICES; YUKAWA POTENTIAL
Citation Formats
Gupta, Akanksha, Ganesh, Rajaraman, Email: ganesh@ipr.res.in, and Joy, Ashwin. Molecular shear heating and vortex dynamics in thermostatted two dimensional Yukawa liquids. United States: N. p., 2016.
Web. doi:10.1063/1.4958943.
Gupta, Akanksha, Ganesh, Rajaraman, Email: ganesh@ipr.res.in, & Joy, Ashwin. Molecular shear heating and vortex dynamics in thermostatted two dimensional Yukawa liquids. United States. doi:10.1063/1.4958943.
Gupta, Akanksha, Ganesh, Rajaraman, Email: ganesh@ipr.res.in, and Joy, Ashwin. 2016.
"Molecular shear heating and vortex dynamics in thermostatted two dimensional Yukawa liquids". United States.
doi:10.1063/1.4958943.
@article{osti_22600034,
title = {Molecular shear heating and vortex dynamics in thermostatted two dimensional Yukawa liquids},
author = {Gupta, Akanksha and Ganesh, Rajaraman, Email: ganesh@ipr.res.in and Joy, Ashwin},
abstractNote = {It is well known that twodimensional 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 molecular dynamics (MD) studies of shear flows in strongly coupled Yukawa liquids indicated the occurrence of strong molecular shear heating, which is found to reduce the coupling strength exponentially leading to the 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 the present work, using MD simulations, a comparative study of shear flow evolution in Yukawa liquids in the presence and absence of molecular or microscopic heating is presented for a prototype shear flow, namely, Kolmogorov flow.},
doi = {10.1063/1.4958943},
journal = {Physics of Plasmas},
number = 7,
volume = 23,
place = {United States},
year = 2016,
month = 7
}

Using a generalized hydrodynamic (GH) model, the growth rate spectra of KelvinHelmholtz (KH) instability has been obtained analytically for a step shear profile in strongly coupled Yukawa liquids. The class of shear flows studied is assumed to be incompressible in nature. The growth rate spectra calculated exhibit viscous damping at high mode numbers, destabilization at stronger coupling, and in the limit {tau}{sub m} (viscoelastic relaxation time){yields}0, reduce to the regular NavierStokes growth rate spectra. A direct comparison is made with previous molecular dynamics (MD) simulations [Ashwin J. and R. Ganesh, Phys. Rev. Lett. 104, 215003 (2010)] of KH instability. Wemore »

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