International Journal of Modern Physics C Vol. 16, No. 12 (2005) 1819–1830 c  World Scientific Publishing Company THREE-DIMENSIONAL LATTICE BOLTZMANN MODEL RESULTS FOR COMPLEX FLUIDS ORDERING G. AMATI * and F. MASSAIOLI † CASPUR, Via dei Tizii 6/b, 00185 Rome, Italy * g.amati@caspur.it † f.massaioli@caspur.it G. GONNELLA ‡ and AIGUO XU § Dipartimento di Fisica, Universit`a di Bari, and INFN, Sezione di Bari Via Amendola 173, 70126 Bari, Italy ‡ gonnella@ba.infn.it § aiguoxu@yuragi.jinkan.kyoto-u.ac.jp A. LAMURA Istituto Applicazioni Calcolo, CNR, Sezione di Bari Via Amendola 122/D, 70126 Bari, Italy a.lamura@ba.iac.cnr.it Received 5 May 2005 Revised 8 June 2005 The kinetics of domain growth of fluid mixtures quenched from a disordered to a lamellar phase has been studied in three dimensions. We use a numerical approach based on the lattice Boltzmann method (LBM). A novel implementation for LBM which “fuses” the collision and streaming steps is used in order to reduce memory and bandwidth requirements. We find that extended defects between stacks of lamellae with different orientation dominate the late time dynamics. Keywords : Lattice Boltzmann method; parallel code; lamellar phase; complex fluids. PACS Nos.: 47.11.+j, 64.75.+g, 47.54.+r, 05.70.Ln. 1. Introduction Hydrodynamics is an essential ingredient in the modelling of complex fluids. Many relevant phenomena in soft matter physics depend on the interplay between the mesoscopic structures in the fluid (interfaces, extended objects like polymers, col- loidal particles, etc.) and the local velocity field. 1 § Present address: Division of Physics and Astronomy, Yoshida-south Campus, Kyoto University, Kyoto 606-8501, Japan. 1819