A hybrid multiscale dissipative particle dynamics method coupling particle and continuum for complex fluid

A hybrid multiscale dissipative particle dynamics (HMDPD) method is proposed for simulating complex fluid, in which dissipative particle dynamics (DPD) is used in the mesoscale flow region and continuum Navier-Stokes equations in the macroscale one. In particular, the variational multiscale method is introduced to overcome the numerical instabilities of the finite element method for solving the Navier-Stokes equations. The spatial coupling between continuum equations and DPD is achieved through constrained dynamics in an overlap region. The Couette flow problem is simulated to verify the proposed HMDPD method. Then, the method is applied to simulate extremely dilute polymer solution in Couette flow. In order to more accurately imitate the polymer chain in the dilute polymer solution, we develop a modified finitely extensible nonlinear elastic chain model, which perfectly describes both the elastic tension and the elastic repulsion between the adjacent beads with bond length as the equilibrium length of one segment. It is found that, using the proposed HMDPD method, not only the macroscopic flow velocity can be calculated, but also the mesoscopic molecular details such as conformational changes as well as dynamic behaviors of polymer chain under the influence of shear flow field can be observed.