Cascades and spectra of a turbulent spinodal decomposition in two-dimensional symmetric binary liquid mixtures

Xiang Fan, P. H. Diamond, L. Chacón, and Hui Li
Phys. Rev. Fluids 1, 054403 – Published 12 September 2016; Erratum Phys. Rev. Fluids 2, 109901 (2017)

Abstract

We study the fundamental physics of cascades and spectra in two-dimensional (2D) Cahn-Hilliard-Navier-Stokes (CHNS) turbulence, and compare and contrast this system with 2D magnetohydrodynamic (MHD) turbulence. The important similarities include basic equations, ideal quadratic invariants, cascades, and the role of linear elastic waves. Surface tension induces elasticity, and the balance between surface tension energy and turbulent kinetic energy determines a length scale (Hinze scale) of the system. The Hinze scale may be thought of as the scale of emergent critical balance between fluid straining and elastic restoring forces. The scales between the Hinze scale and dissipation scale constitute the elastic range of the 2D CHNS system. By direct numerical simulation, we find that in the elastic range, the mean square concentration spectrum Hkψ of the 2D CHNS system exhibits the same power law (7/3) as the mean square magnetic potential spectrum HkA in the inverse cascade regime of 2D MHD. This power law is consistent with an inverse cascade of Hψ, which is observed. The kinetic energy spectrum of the 2D CHNS system is EkKk3 if forced at large scale, suggestive of the direct enstrophy cascade power law of 2D Navier-Stokes turbulence. The difference from the energy spectra of 2D MHD turbulence implies that the back reaction of the concentration field to fluid motion is limited. We suggest this is because the surface tension back reaction is significant only in the interfacial regions. The interfacial regions fill only a small portion of the 2D CHNS system, and their interface packing fraction is much smaller than that for 2D MHD.

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  • Received 6 April 2016

DOI:https://doi.org/10.1103/PhysRevFluids.1.054403

©2016 American Physical Society

Physics Subject Headings (PhySH)

Fluid DynamicsPlasma Physics

Erratum

Authors & Affiliations

Xiang Fan and P. H. Diamond

  • University of California at San Diego, La Jolla, California 92093, USA

L. Chacón and Hui Li

  • Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

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Issue

Vol. 1, Iss. 5 — September 2016

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