Hybrid atomistic-continuum formulations and the moving contact-line problem

We present a hybrid atomistic-continuum computational framework for the tre atment of dense fluid problems with emphasis on the coupling of molecular d ynamics with continuum (finite element/spectral) methods for problems invol ving multi-fluid dynamics in the presence of multi-fluid interfaces. The te chnique is an extension of the single-fluid framework already presented by the author. The well-known moving contact-line problem is used as a validat ion example. A hybrid solution that employs molecular dynamics close to the walls where molecular effects are important and continuum fluid mechanics in the remainder of the domain (far field region) is obtained. A fully mole cular solution of the same problem serves as an exact solution. Various iss ues related to dense fluid atomistic-continuum techniques are discussed and contrasted to the already existing but less general dilute gas techniques. Numerical considerations are discussed with particular emphasis on efficie ncy, and a formulation that reduces computational cost is proposed. (C) 199 9 Academic Press.