Chorin's Projection Method for Finite Volume
 

Hello,
I am attempting to implement Chorin's projection method using the finite-volume method in Cartesian coordinates. I am having difficulty constructing the poisson equation for the pressure. When I attempt the define the div(grad P) it appears that I need to reference at least two cells outside of the computational domain. Does this sound right? Can anyone direct me to a text or example?

Thanks,
Scott

extrapolation
 

from inner domain cells