Transp Porous Med DOI 10.1007/s11242-012-0054-5 Effect of Mean Network Coordination Number on Dispersivity Characteristics Leonid Vasilyev · Amir Raoof · Jan M. Nordbotten Received: 21 August 2011 / Accepted: 21 July 2012 © Springer Science+Business Media B.V. 2012 Abstract In this study, we investigate the role of topology on the macroscopic (centimeter scale) dispersion characteristics derived from pore-network models. We consider 3D random porous networks extracted from a regular cubic lattice with coordination number distributed in accordance with real porous structures. We use physically consistent rules including ideal mixing in pore bodies, molecular diffusion, and Taylor dispersion in pore throats to simulate transport at the pore-scale level. Fundamental properties of porous networks are based on statistical distributions of basic parameters. Theoretical calculations demonstrate strong cor- respondence with data obtained from numerical experiments. For low coordination numbers, we observe normal transport in porous networks. Anomalous effects expressed by tailing in concentration evolution are seen for higher coordination numbers. We find that the mean network coordination number has significant influence on averaged characteristics of porous networks such as geometric and hydraulic dispersivity, while other topological properties are of less significance. We give an explicit formula that describes the decrease of geometric dis- persivity with growing mean coordination number. The results demonstrate the importance of network topology for models for flow and transport in porous media. Keywords Dispersion · Porous media · Pore-network models · Coordination number 1 Introduction Transport phenomena of passive solutes in porous media are important in many problems of scientific and industrial interest, including transport of contaminants in soils and aquifers, extraction of oil and gas, geothermal energy, and carbon dioxide storage. Realistic models L. Vasilyev (B ) · J. M. Nordbotten Department of Mathematics, University of Bergen, Joh. Brunsgate, 12, 5008 Bergen, Norway e-mail: leonid.vasilyev@uib.no A. Raoof Universiteit Utrecht, Budapestlaan 4, 3584 CD, Utrecht, The Netherlands e-mail: raoof@geo.uu.nl 123