help needed on fluxes

zhu

hi,there, I want to simulate the fluid field around a hexagonal section using the FVM and projection method(incompressible),when I deduce the FVM difference formuation,i met a problem: in order to expedite the code,i must use MG method,so the mesh which can be formed by Phoenics is appreciated,in which grid are in Cartesian coordinates but not all mesh are orthogonal,in other word,non-orthogonal Cartesian coordinate system with unequal grid space,when i integrate the equ. over the finite volume and after applying the Green's theoren,the advective term (dE/dx,dF/dy) now become E and F ,which are the fluxes on the center of the interface of the finite volume,while the diffusion term can be integrated without any difficulty,the difficult is how can i determine the spatial values of the fluxes on the interface of the finite volume,for the accuracy and stablity,i cannot use the averaged values(central difference) and first order upwind scheme,i donot know how to deal with this problem,how the Phoenics deals with this kind of problemes,does it use hybrid scheme(Patankar)?how the bybrid scheme works on non-orthogonal Cartesian coordinate system with unequal grid space on FVM.