A note on equilibrium boundary conditions in lattice Boltzmann fluid dynamic simulations
Department of Mechanical and Manufacturing Engineering, Schulich School of Engineering, The University of Calgary, Calgary, AB, Canada
2 CNR, IAC, Viale del Policlinico 137, T-00161 Roma, Italy
It is shown that Lattice Boltzmann (LB) simulations using simple equilibrium boundary conditions at solid walls, provide quantitatively accurate results for backward-facing step flows at moderate Reynolds numbers. The basic reason for such favorable behavior is that well-resolved LB simulations operate in the so-called weak non-equilibrium regime, in which shear effects at the scale of a single lattice spacing are weak, meaning by this that the cell-shear time scale is much longer than the molecular time scales, so that the LB collisional relaxation takes place in a quasi-homogeneous velocity field. Due to their simplicity, it is suggested that equilibrium boundary conditions may represent a viable option for the LB simulation of complex flows with solid boundaries at moderate Reynolds numbers.
© EDP Sciences, Springer-Verlag, 2009