Numerical investigations on the compressibility of a DPD fluid

The compressibility of a dissipative particle dynamics (DPD) fluid is studied numerically through several newly developed test models, where both the density and the divergence of the velocity field are considered. In the case of zero conservative force, the DPD fluid turns out to be compressible. Effects of the compressibility are observed to be reduced as the particle mass is chosen to be smaller and the system temperature to be higher. In the case of non-zero conservative force, the condition of constant density and divergence-free of velocity can be approximately achieved at large values of the repulsion parameter (i.e., weakly compressible flow). Furthermore, the speed of sound and local Mach number are computed and found to be in good agreement with the theoretical estimation.