Uth, Marc-FlorianMarc-FlorianUthCrüger, AlfAlfCrügerHerwig, HeinzHeinzHerwig2020-05-052020-05-052013Proceedings of the ASME 11th International Conference on Nanochannels, Microchannels, and Minichannels - 2013 : single phase gas flow ... / presented at ASME 2013 11th International Conference on Nanochannels, Microchannels and Minichannels ; June 16 - 19, 2013 Sapporo, Japan / sponsored by ASME. - New York, NY : ASME, 2013. - Paper no. ICNMM2013-73026, V001T12A001; 8 pageshttp://hdl.handle.net/11420/6045In micro or nano flows a slip boundary condition is often needed to account for the special flow situation that occurs at this level of refinement. A common model used in the Finite Volume Method (FVM) is the Navier-Slip model which is based on the velocity gradient at the wall. It can be implemented very easily for a Navier-Stokes (NS) Solver. Instead of directly solving the Navier-Stokes equations, the Lattice-Boltzmann method (LBM) models the fluid on a particle basis. It models the streaming and interaction of particles statistically. The pressure and the velocity can be calculated at every time step from the current particle distribution functions. The resulting fields are solutions of the Navier-Stokes equations. Boundary conditions in LBM always not only have to define values for the macroscopic variables but also for the particle distribution function. Therefore a slip model cannot be implemented in the same way as in a FVM-NS solver. An additional problem is the structure of the grid. Curved boundaries or boundaries that are non-parallel to the grid have to be approximated by a stairlike step profile. While this is no problem for no-slip boundaries, any other velocity boundary condition such as a slip condition is difficult to implement. In this paper we will present two different implementations of slip boundary conditions for the Lattice-Boltzmann approach. One will be an implementation that takes advantage of the microscopic nature of the method as it works on a particle basis. The other one is based on the Navier-Slip model. We will compare their applicability for different amounts of slip and different shapes of walls relative to the numerical grid. We will also show what limits the slip rate and give an outlook of how this can be avoided. Copyright © 2013 by ASME.enTechnikIngenieurwissenschaftenConference Paper10.1115/ICNMM2013-73026Other