Fully Atomistic Simulations of Hydrodynamic Instabilities and Mixing

The large-scale computational capabilities at LLNL make it possible to develop seamless connections from processes at the atomic scale to complex macroscopic phenomena such as hydrodynamic instabilities and turbulent mixing. Traditionally, these connections have been made by combining results from different scientific fields. For gases and fluids, atomic and molecular scattering cross sections must first be obtained and incorporated into Boltzmann transport equations. Their solution yields then transport coefficients which are input parameters for the Navier-Stokes equations for fluid dynamics. The latter are solved numerically with hydro-codes. For visco-elastic solids, on the other hand, atomistic simulations must first provide constitutive laws for the mobility and multiplication of dislocations and other crystalline defects. In turn, these laws are utilized to construct meso-scale models for plastic deformation. These models are then incorporated into hydro- and finite element codes to predict the macroscopic behavior of solid materials. Many of these intermediate steps can be bypassed with large-scale molecular dynamics simulations. For this purpose, codes have been developed in which trajectories of atoms or molecules are mapped onto continuum field descriptions for mass density, mass flow, stresses, and for temperature. It is now possible to compare directly and quantitatively atomistic simulations with predictions frommore » hydro- and finite element codes and with experimental results.« less