Implementation of the FCHC lattice gas model on the Connection Machine

The 4-dimensional FCHC lattice gas model has been implemented on a Connection Machine CM-2 with 16K processors. Symmetries are used to reduce the collision table to a size that fits into local memory. This method avoids the degradation of the Reynolds coefficientR_*, but at the price of increased computing time. Bit shuffling between parallel lattices is introduced to reduce the discrepancy between measured viscosities and those predicted from the Boltzmann approximation. Thereby a model with a negative shear viscosity is obtained: a fluid having a uniform initial velocity is unstable and organized nonuniform motions develop. Because of the buildup of very strong correlations between the parallel lattices, the discrepancy with the Boltzmann values decreases only very slowly with the number of parallel lattices.