Re: FreeSlip Boundary Condition – Implementation Doubts
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Hi Robin,rnrnThank you for your response. I have not been tried to implement the addConvectionBoundary function of the class sOnLatticeBoundaryCondition2D. I have already read your paper Inertial dilute particulate fluid flow simulations with an Euler–Euler lattice Boltzmann method, where you implemented this convectionboundary in order to simulate an outflow condition. It seems that “”advectionDiffusionBoundayPostProcessiorXD.h/hh”” it is only implemented in 3D, right? rnrnIn the case of freeslip, if “”U“”is the velocity vector and “”n“” is the normal vector to the boundary pointing outwards, the grad(U)*n = 0 (0 is the zero vector). Thus, if I am not wrong, the outflow condition of your paper should not be applied for this kind of boundary.rnrnI checked the addSlipBoundary function available in olb::sOnLatticeBoundaryCondition2D< T, Lattice > Class Template Reference. The processSubDomain, located in SlipBoundaryProcessor2D, works as the specular reflection approach explained by myself at the beginning of this post. However, I do not understand why the corner nodes are treated as a bounceback for the diagonal direction and the vertical and horizontal are switched 90°. For example, for a D2Q9 lattice and the NorthWest node, the distributions changed are :rn

f4 = f2rnf5 = f1rnf6 = f8
rnrnIt should be noted that the lattice arrangement is:rn
rnrnAs pointed out by in Question about Cavity2d Example and How to set a slip boundary posts, it seems that the nodes residing in the overlap region could not be implemented as a SlipBoundaryCondition. Does someone know how to “”fix”” or overcome this problem?rnrnFinally, the user guide indicates that createInterpBoundaryConditionXD is the default nonlocal boundary condition based in the work of Skordos (1993). It seems that “”StraightFdBoundaryProcessor2D“” and “”PlaneFdBoundaryProcessor3D“” correspond to the postprocessing classes for 2D and 3D, respectively. Does someone know how theses classes are accessed by the createInterpBoundaryConditionXD object ? Because from the sOnLatticeBoundaryConditionXD class only the velocity/pressure/slip/convection boundary functions are available. rnrnBest regards,rnAlejandrorn