TABLE OF CONTENTS Recent development of micro and nano systems has been attracting the attention of researchers in many different areas. Flows in micro and nano mechanics systems are often very complex in nature, and usually involve multi-scales and multi-phases. One of the major outstanding challenges in the simulation of complex fluid flows is the necessity of a systematic frame, which bridges the gap between nano, micro, meso and macro scales for physics on multiple scales. Coupling length scale (CLS) is very important for such simulations and is usually implemented by combining different approaches to account for the different phenomena that dominate. One example is the flows in nano and microfluidic devices. Modeling the flows in micro devices with molecular dynamics (MD) is impractical since the usual atomistic MD simulations are limited to very small length scale over very short times. Application of the macro continuum numerical methods such as the finite element method (FEM), finite difference method (FDM) and finite volume method (FVM) is invalid for the atomistic regions due to the continuum assumptions. Coupling the atomistic molecular dynamics with the continuum methods tends to be a good approach for multiple scale computations. In the coupling practice, MD is employed for atomistic regions with inhomogeneities and complex features, and a continuum approach is used for other regions.
Coupling atomistic and continuum simulation for solids is well investigated and widely practiced (Broughton, 1999; Rudd and Broughton, 1999; Smirnova, 1999). It is especially popular in fracture mechanics for simulating micro crack initiation...
