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Low Mach number fluctuating hydrodynamics model for ionic liquids

Katherine Klymko, Andrew Nonaka, John B. Bell, Sean P. Carney, and Alejandro L. Garcia
Phys. Rev. Fluids 5, 093701 – Published 18 September 2020
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Abstract

We present a new mesoscale model for ionic liquids based on a low Mach number fluctuating hydrodynamics formulation for multicomponent charged species. The low Mach number approach eliminates sound waves from the fully compressible equations leading to a computationally efficient incompressible formulation. The model uses a Gibbs free-energy functional that includes enthalpy of mixing, interfacial energy, and electrostatic contributions. These lead to a new fourth-order term in the mass equations and a reversible stress in the momentum equations. We calibrate our model using parameters for [DMPI+][F6P-], an extensively studied room temperature ionic liquid (RTIL), and numerically demonstrate the formation of mesoscopic structuring at equilibrium in two and three dimensions. In simulations with electrode boundaries the measured double-layer capacitance decreases with voltage, in agreement with theoretical predictions and experimental measurements for RTILs. Finally, we present a shear electroosmosis example to demonstrate that the methodology can be used to model electrokinetic flows.

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  • Received 23 June 2020
  • Accepted 24 August 2020

DOI:https://doi.org/10.1103/PhysRevFluids.5.093701

©2020 American Physical Society

Physics Subject Headings (PhySH)

Fluid Dynamics

Authors & Affiliations

Katherine Klymko

  • Computational Chemistry, Materials, and Climate, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA

Andrew Nonaka* and John B. Bell

  • Center for Computational Sciences and Engineering, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA

Sean P. Carney

  • Department of Mathematics, University of California, Los Angeles, Los Angeles, California 90095, USA

Alejandro L. Garcia

  • Department of Physics and Astronomy, San Jose State University, San Jose, California 95192, USA

  • *AJNonaka@lbl.gov

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Issue

Vol. 5, Iss. 9 — September 2020

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