Adjoint-consistent formulations of slip models for coupled electroosmotic flow systems

Background: Models based on the Helmholtz ‘slip’ approximation are often used for the simulation of electroosmotic flows. The objectives of this paper are to construct adjoint-consistent formulations of such models, and to develop adjoint-based numerical tools for adaptive mesh refinement and parameter sensitivity analysis.

Methods: We show that the direct formulation of the ‘slip’ model is adjoint inconsistent, and leads to an ill-posed adjoint problem. We propose a modified formulation of the coupled ‘slip’ model, which is shown to be well-posed, and therefore automatically adjoint-consistent.

Results: Numerical examples are presented to illustrate the computation and use of the adjoint solution in two-dimensional microfluidics problems.

Conclusions: An adjoint-consistent formulation for Helmholtz ‘slip’ models of electroosmotic flows has been proposed. This formulation provides adjoint solutions that can be reliably used for mesh refinement and sensitivity analysis.

Uncontrolled Keywords

• Adjoint techniques
• Electroosmosis
• Microfluidics
• Slip boundary conditions