(450c) Application of the Lattice Boltzmann Method to Many Particle Dispersions

We have discussed the feasibility of the lattice Boltzmann method as a simulation technique with multi-body hydrodynamic interactions for many particle dispersions, by considering aggregation phenomena in a two-dimensional suspension composed of magnetic particles. In concrete, lattice Boltzmann simulations have been carried out under various situations for clarifying whether or not the translational and rotational Brownian motion can be activated on a physically reasonable level. The validity of the present results has been discussed by comparing with those of Monte Carlo and Brownian dynamics simulations. The results obtained here are summarized as follows. The density ratio between magnetic particles and the ambient liquid does not significantly influence the cluster formation. If relatively coarse lattices are used, physically reasonable aggregate structures can be obtained, but if fine lattices are adopted, the particle Brownian motion cannot be activated properly, which causes invalid aggregate formation of particles. The results concerning the pair correlation function and magnetization curves clearly show that the lattice Boltzmann results are in good agreement with those of Monte Carlo and Brownian dynamics methods. We may conclude from these results that, if relatively coarse lattice systems are used, the translational and rotational Brownian motion of particles are reasonably activated, but if fine lattice system are adopted, the lattice Boltzmann method cannot give rise to physically reasonable results. Hence, some modifications to the basic equations of the lattice Boltzmann method are necessary for using fine lattice systems for simulations of magnetic dispersions.