“…Our primary concern is with averages defined for each phase at every position in the porous media. The approach taken here is to speak in terms of local volume averages at each point in the structure (Slattery, 1967(Slattery, , 1968(Slattery, , 1969(Slattery, , 1970(Slattery, , 1981Patel et al, 1972;Sha and Slattery, 1980; Anderson and Jackson, 1967;Whitaker, 1969Whitaker, , 1973Bear, 1972;Bachmat, 1972;Gray, 1975; Gray and O'Neill, 1976; Gray and Lee, 1977;Hassanizadah and Gray, 1979). …”