Movable Automata for Simulation of Boundary Conditions and Shear Flow of Fluids Systems

The present work aims to develop a simple simulation tool capable of modeling the boundary conditions between a solid and a fluid. We study friction between two atomically flat surfaces composed of particles of different sizes and separated by a model fluid formed by moving particles with repulsing cores of different sizes and a long-range attraction.The suggested simulation method is shown to demonstrate realistic behavior at different parameters of interaction and loading, such as temperature, external pressure and mutual relative velocity of the surface plates. A systematic study of the model is performed for a system with uniformly sized particles. It is shown that fluid particles can form different (solid, liquid and gaseous) states, depending on the effective temperature (kinetic energy, caused by surface motion and random noise generated by spatially distributed Langevin sources). The behavior of the system is determined by two main factors: the relative radius of the “fluid” and “surface” particles and by the parameters of adhesive interaction. Heating the region close to one of the plates can change the density of the liquid in its proximity and result in chaotization (turbulence), and also dramatically change the configuration, the direction of the average flow, and reduce effective friction force.