Computing bulk and shear viscosities from simulations of fluids with dissipative and stochastic interactions

摘要

Exact values for bulk and shear viscosity are important to characterize afluid and they are a necessary input for a continuum description. Here wepresent two novel methods to compute bulk viscosities by non-equilibriummolecular dynamics (NEMD) simulations of steady-state systems with periodicboundary conditions -- one based on frequent particle displacements and onebased on the application of external bulk forces with an inhomogeneous forceprofile. In equilibrium simulations, viscosities can be determined from the stresstensor fluctuations via Green-Kubo relations; however, the correctincorporation of random and dissipative forces is not obvious. We discussdifferent expressions proposed in the literature and test them at the exampleof a dissipative particle dynamics (DPD) fluid.