I need to learn FDM more than the introductory level which I learned from classes. Is there a good, conprehensive book that covers every aspect of FDM in groundwater flow problems? Such as the difference of block- verse point-centered scheme in terms of applying boundary conditions? I like to learn about the block-centered scheme and how both the specified head/flux with this scheme is applied. I'm trying to apply Periodic Boundary Condtion (PBC) to a 2D flow domain, in which case, the boundary is neigher specified head, nor specified flux, but the boundary node is related to the internal nodes by the PBC. Thus how to treat the boundary is important. Thanks!

I may be able to provide a little information on periodic BC.

suppose we have a box and the left edge is periodic to the right edge.

PBC means the values and derivatives on one edge of boundary is the same as another edge of boundary.

this is equivalent to say: the value on the left edge is the same as the value on the right edge; and, the value on the left of the left edge is the same as the value on the left of the right edge.

in this way, the derivatives are on longer needed.

PBC in fact is the easiest to implement in FDM

Thanks very much! I've since learned more about PBC... How about a good book on FDM (in fluid flow, heat transfer and solute transport or reaction)?