INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS Int. J. Numer. Meth. Fluids 2007; 55:537–564 Published online 28 February 2007 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/fld.1468 Critical evaluation of CFD codes for interfacial simulation of bubble-train flow in a narrow channel Furkan ¨ Ozkan 1, 2, 3, ∗, † , Martin W¨ orner 2 , Achim Wenka 3 and Hakan S. Soyhan 4 1 University of Sakarya, Institute of Science and Technology, Sakarya, Turkey 2 Forschungszentrum Karlsruhe, Institut f¨ ur Reaktorsicherheit, Karlsruhe, Germany 3 Forschungszentrum Karlsruhe, Institut f¨ ur Mikroverfahrenstechnik, Karlsruhe, Germany 4 Engineering Faculty, Mechanical Engineering Department, University of Sakarya, Sakarya, Turkey SUMMARY Computational fluid dynamics (CFD) codes that are able to describe in detail the dynamic evolution of the deformable interface in gas–liquid or liquid–liquid flows may be a valuable tool to explore the potential of multi-fluid flow in narrow channels for process intensification. In the present paper, a computational exercise for co-current bubble-train flow in a square vertical mini-channel is performed to investigate the performance of well-known CFD codes for this type of flows. The computations are based on the volume-of-fluid method (VOF) where the transport equation for the liquid volumetric fraction is solved either by the methods involving a geometrical reconstruction of the interface or by the methods that use higher-order difference schemes instead. The codes contributing to the present code-to-code comparison are an in-house code and the commercial CFD packages CFX, FLUENT and STAR-CD. Results are presented for two basic cases. In the first one, the flow is driven by buoyancy only, while in the second case the flow is additionally forced by an external pressure gradient. The results of the code-to-code comparison show that only the VOF method with interface reconstruction leads to physically sound and consistent results, whereas the use of difference schemes for the volume fraction equation shows some deficiencies. Copyright 2007 John Wiley & Sons, Ltd. Received 5 October 2006; Revised 24 January 2007; Accepted 27 January 2007 KEY WORDS: micro-process engineering; code-to-code comparison; volume-of-fluid method; bubble- train flow; Taylor flow; square channel ∗ Correspondence to: Furkan ¨ Ozkan, Forschungszentrum Karlsruhe, Institute for Micro Process Engineering, P.O. Box 3640, Karlsruhe 76021, Germany. † E-mail: oezkan@imvt.fzk.de Contract/grant sponsor: EU Erasmus program Contract/grant sponsor: Institute of Science and Technology at Sakarya University Copyright 2007 John Wiley & Sons, Ltd.