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Stable finite element approximation of a Cahn–Hilliard–Stokes system coupled to an electric field

Published online by Cambridge University Press:  09 September 2016

ROBERT NÜRNBERG
Affiliation:
Department of Mathematics, Imperial College London, London, SW7 2AZ, UK emails: robert.nurnberg@imperial.ac.uk, e.tucker08@imperial.ac.uk
EDWARD J. W. TUCKER
Affiliation:
Department of Mathematics, Imperial College London, London, SW7 2AZ, UK emails: robert.nurnberg@imperial.ac.uk, e.tucker08@imperial.ac.uk

Abstract

We consider a fully practical finite element approximation of the Cahn–Hilliard–Stokes system:

$$\begin{align*} \gamma \tfrac{\partial u}{\partial t} + \beta v \cdot \nabla u - \nabla \cdot \left( \nabla w \right) & = 0 \,, \quad w= -\gamma \Delta u + \gamma ^{-1} \Psi ' (u) - \tfrac12 \alpha c'(\cdot,u) | \nabla \phi |^2\,, \\ \nabla \cdot (c(\cdot,u) \nabla \phi) & = 0\,,\quad \begin{cases} -\Delta v + \nabla p = \varsigma w \nabla u, \\ \nabla \cdot v = 0, \end{cases} \end{align*}$$
subject to an initial condition u0(.) ∈ [−1, 1] on the conserved order parameter u ∈ [−1, 1], and mixed boundary conditions. Here, γ ∈ $\mathbb{R}_{>0}$ is the interfacial parameter, α ∈ $\mathbb{R}_{\geq0}$ is the field strength parameter, Ψ is the obstacle potential, c(⋅, u) is the diffusion coefficient, and c′(⋅, u) denotes differentiation with respect to the second argument. Furthermore, w is the chemical potential, φ is the electro-static potential, and (v, p) are the velocity and pressure. The system has been proposed to model the manipulation of morphologies in organic solar cells with the help of an applied electric field and kinetics.

Type
Papers
Copyright
Copyright © Cambridge University Press 2016 

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