Parallel implementation of the fluid particle model for simulating complex fluids in the mesoscale

Dissipative particle dynamics (DPD) and its generalization – the fluid particle model (FPM) represent the “fluid particle” approach for simulating fluid-like behavior in the mesoscale. Unlike particles from molecular dynamics (MD) method, the “fluid particle” can be viewed as a “droplet” consisting of liquid molecules. In FPM, “fluid particles” interact by both central and non-central, short-range forces with conservative, dissipative and Brownian character. In comparison to MD, FPM method in 3-D requires two to three times more memory load and three times more communication overhead. Computational load per step per particle is comparable to MD due to the shorter interaction range allowed between “fluid particles” than between MD atoms. The classical linked-cells technique and decomposing the computational box into strips allow for rapid modifications of the code and for implementing non-cubic computational boxes. We show that the efficiency of the FPM code depends strongly on the number of particles simulated, geometry of the box, and the computer architecture. We give a few examples from long FPM simulations involving up to 8 million fluid particles and 32 processors. Results from FPM simulations in 3-D of the phase separation in binary fluid and dispersion of colloidal slab are presented. Scaling law for symmetric quench in phase separation has been properly reconstructed. We show also that the microstructure of dispersed fluid depends strongly on the contrast between kinematic viscosities of this fluid phase and the bulk phase. This FPM code can be applied for simulating mesoscopic flow dynamics in capillary pipes or critical flow phenomena in narrow blood vessels.