Comparison of boundary slip for two variants of immersed boundary method in lattice Boltzmann framework

In this paper, the Immersed Moving Boundary-Lattice Boltzmann (IMB-LB) method is compared with the single relaxation time and multiple-relaxation-time versions of the Immersed Boundary-Lattice Boltzmann (IB-LB) method in terms of the amount of numerical velocity slip produced on solid boundaries. The comparisons are performed for both straight and curved boundaries based on the effects of thickness of virtual domain used in the IB method for the first time, and relaxation time parameter(s) of the LB method. For the straight boundaries, a shear flow problem is studied while for the curved boundaries, a falling circular cylinder in an infinite channel is investigated. First, sensitivities of the IB-LB and IMB-LB methods to the relaxation time parameter(s) and thickness of virtual domain are presented. Then, the interaction of two solid particles in a shear flow is studied to assess the validity of arguments presented in solving a typical practical problem.