sos: what is the quasiperiodic boundary conditions?

Lattice Boltzmann Method LBM: Theory
#1

Now, i am studying the two-phase fluid flow. I want to simulate the drainage (or imbibition) process, however , i do not know what is the quasiperiodic boundary conditions? And how to use the quasiperiodic boundary conditions in LBM code?

In the paper (Martys and Chen ,1996), he described the quasiperiodic boundary conditions as following:

" In this simulation quasiperiodic boundary conditions were maintained in the direction of the applied force such that any fluid exiting the porous medium reenters at the inlet and is converted to (or relabeled as) the injected wetting (nonwetting) fluid".

Could anybody tell me how to use the quasiperiodic boundary conditions in LBM code?

Thank you!

PS: Nicos S. Martys and Hudong chen. Simulation of multicomponent fluids in complex three-dimensional geometries by the lattice Boltzmann method. Physical Review E. 1996

#2

I briefly looked at the paper and as far as I can tell they just used this boundary condition so that the mass of each fluid is conserved within the volume. All the water (or what ever second phase they try to simulate) that leaves the domain through the outlet enters it again via the inlet. If you want to reproduce their results you would have to write your own little routine as far as I can see it. It shouldn’t be very difficult to do with OpenLB although I didn’t use the multispecies model yet.