Upscaling: a review

Porous media have properties with heterogeneities on several length scales. It is possible to build digital models of such properties. However these can be so detailed that a computing machine of the same power as that used to build the property model is not able to solve the fluid flow equations using standard discretisation methods-storage is needed for workspace, and the discrete equations have to be solved in a reasonable time. This paper reviews averaging techniques, devised to simulate large scale features of solutions without necessarily solving all the fine scale equations. Copyright (C) 2002 John Wiley Sons, Ltd.