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# Communications in Mathematical Sciences

## Volume 13 (2015)

### Number 6

### On the Cahn–Hilliard–Brinkman system

Pages: 1541 – 1567

DOI: http://dx.doi.org/10.4310/CMS.2015.v13.n6.a9

#### Authors

#### Abstract

We consider a diffuse interface model for phase separation of an isothermal, incompressible, binary fluid in a Brinkman porous medium. The coupled system consists of a convective Cahn–Hilliard equation for the phase field $\phi$, i.e., the difference of the (relative) concentrations of the two phases coupled with a modified Darcy equation proposed by H.C. Brinkman in 1947 for the fluid velocity $u$. This equation incorporates a diffuse interface surface force proportional to $\phi \nabla \mu$ where $\mu$ is the so-called chemical potential. We analyze the well-posedness of the resulting Cahn–Hilliard–Brinkman (CHB) system for $(\phi, u)$. Then we establish the existence of a global attractor and the convergence of a given (weak) solution to a single equilibrium via a Łojasiewicz–Simon inequality. Furthermore, we study the behavior of the solutions as the viscosity goes to zero, that is, when the CHB system approaches the Cahn–Hilliard–Hele–Shaw (CHHS) system. We first prove the existence of a weak solution to the CHHS system as limit of CHB solutions. Then, in dimension two, we estimate the difference of the solutions to CHB and CHHS systems in terms of the viscosity constant appearing in CHB.

#### Keywords

incompressible binary fluids, Brinkman equation, Darcy’s law, diffuse interface models, Cahn–Hilliard equation, weak solutions, existence, uniqueness, global attractor, convergence to equilibrium, vanishing viscosity

#### 2010 Mathematics Subject Classification

35B40, 35D30, 35Q35, 37L30, 76D27, 76D45, 76S05, 76T99

Published 13 May 2015