Modified periodic-shell boundary condition for dissipative particle dynamics simulations

We have developed the modified periodic-shell boundary condition (BC) for dissipative particle dynamics (DPD) simulations, which enables us to simulate an outer flow problem around an obstacle using a small simulation region. In order to clarify the validity of this BC, we have treated a uniform flow past a circular cylinder. The present BC has been compared with the ordinary BC such as the uniform flow condition. Also, the present results have been compared with those of the numerical results of the Navier–Stokes equation. The ordinary uniform BC is seen to give rise to significantly distorted flow fields and also to significant disappearance of dissipative particles from the simulation region. In contrast, for the present modified periodic-shell BC, the number density of dissipative particles is kept almost constant during a simulation run, and the flow field is in reasonable agreement with the result, which has been obtained by numerical simulations of the Navier–Stokes equation.