Global well-posedness and convergence to equilibrium for the Abels-Garcke-Gr\"{u}n model with nonlocal free energy

TL;DR

This paper proves the global existence, uniqueness, and convergence to equilibrium of solutions for a nonlocal fluid mixture model, extending the understanding of complex fluid dynamics with singular potentials and interface diffusion.

Contribution

It introduces novel well-posedness results for the nonlocal convective Cahn-Hilliard equation with singular potential and minimal assumptions, and establishes convergence and stability properties of solutions.

Findings

Global strong solutions exist in 2D domains.

Weak solutions propagate regularity and converge to equilibrium.

Strong solutions are unique and depend continuously on initial data.

Abstract

We investigate the nonlocal version of the Abels-Garcke-Gr\"{u}n (AGG) system, which describes the motion of a mixture of two viscous incompressible fluids. This consists of the incompressible Navier-Stokes-Cahn-Hilliard system characterized by concentration-dependent density and viscosity, and an additional flux term due to interface diffusion. In particular, the Cahn-Hilliard dynamics of the concentration (phase-field) is governed by the aggregation/diffusion competition of the nonlocal Helmholtz free energy with singular (logarithmic) potential and constant mobility. We first prove the existence of global strong solutions in general two-dimensional bounded domains and their uniqueness when the initial datum is strictly separated from the pure phases. The key points are a novel well-posedness result of strong solutions to the nonlocal convective Cahn-Hilliard equation with singular potential and constant mobility under minimal integral assumption on the incompressible velocity field, and a new two-dimensional interpolation estimate for the $L^4(\Omega)$ control of the pressure in the stationary Stokes problem. Secondly, we show that any weak solution, whose existence was already known, is globally defined, enjoys the propagation of regularity and converges towards an equilibrium (i.e., a stationary solution) as $t\rightarrow \infty$. Furthermore, we demonstrate the uniqueness of strong solutions and their continuous dependence with respect to general (not necessarily separated) initial data in the case of matched densities and unmatched viscosities (i.e., the nonlocal model H with variable viscosity, singular potential and constant mobility). Finally, we provide a stability estimate between the strong solutions to the nonlocal AGG model and the nonlocal Model H in terms of the difference of densities.