Finite difference and Periodic Boundary Condition

Linda

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!