“…These length scale constraints were introduced for proper upscaling based on the pioneering work of several researchers including (Whitaker, Gray, Hassanizadeh, Bear, Bachmat, Quintard, Slattery, Cushman, Marle and many others). Recently, (Salama & van Geel, 2008a) have postulated the conditions required for proper upscaling such that one may get the correct set of equations subject to the constraints pertinent to adhering to these conditions, as will be explained later. This set of macroscopic point equations, in which macroscopic field variables are defined at yet a larger scale than their microscopic counterpart, represents the governing conservation laws at the new macroscale.…”