Journal of Computational Physics 152, 493–516 (1999) Article ID jcph.1999.6242, available online at http://www.idealibrary.com on An Integer Lattice Realization of a Lax Scheme for Transport Processes in Multiple Component Fluid Flows Sauro Succi, ∗ Hudong Chen,† Chris Teixeira,† Gino Bella,‡ A. De Maio,‡ and Kim Molvig§ ∗ Instituto Applicazioni Calcolo, 137 Viale Policlinico, Rome, Italy 00144; †Exa Corporation, 450 Bedford Street, Lexington, Massachusetts 02173; ‡Department of Mechanical Engineering, University of Rome “Tor Vergata,” Rome, Italy; §Department of Nuclear Engineering, Massachusetts Institute of Technology, Memorial Drive, Cambridge, Massachusetts 02139 Received August 17, 1998; revised February 2, 1999 A Lax–Wendroff-like finite-difference representation for the transport of multiple chemical components is formulated via integer variables. This representation en- sures exactly the desired conservation laws at all times and achieves low numerical diffusivity. The algorithm requires less memory as compared to its floating-point pre- decessor, hence much less than standard lattice gas and lattice Boltzmann methods to date. Analytical and numerical studies demonstrate that the algorithm is stable under subsonic conditions. c  1999 Academic Press 1. INTRODUCTION The importance of computation with integer representations has become rapidly rec- ognized since the emergence of lattice gas (LG) and lattice Boltzmann (LB) methods for computational fluid dynamics [1–8]. The most obvious reasons for this include less compu- tational memory requirements and better consistency with modern computer architectures. More importantly, such representations are free of roundoff errors, so that fundamental con- servation laws can be exactly enforced at all times. This is highly desirable in circumstances such as stiff and very long time numerical computations, in which error accumulation may severely affect the quality of the results. We are particularly interested in the simulation of reacting flows, possibly involving a significant number of chemical components, each at a different density and evolving on disparate spatial and time scales. As a result, exact preservation of the conservation properties becomes crucial in order to produce an accurate simulation [9]. 493 0021-9991/99 $30.00 Copyright c  1999 by Academic Press All rights of reproduction in any form reserved.