Transverse effect on liquid viscosity: A many-body dissipative particle dynamics simulation study

Fluid viscosity plays an important role in multiphase flows, and the many-body dissipative particle dynamics (MDPD) method is an efficient means of simulating such flows at the mesoscopic scale. As the viscosity of the standard MDPD (S-MDPD) fluid cannot be efficiently adjusted, a transverse MDPD (T-MDPD) scheme is newly proposed to tune the viscosity of an MDPD fluid over a large range. With a lateral friction coefficient added to the S-MDPD form, the viscosity of the T-MDPD fluid is higher than that of an S-MDPD fluid, and the viscosity is about five times larger than that of an S-MDPD fluid with a friction coefficient of 40.5. In a T-MDPD fluid, the viscosity is much more sensitive to the new transverse friction coefficient, as it increases about five times higher when this coefficient increases from 4.5 to 40.5, while the viscosity only increases two times higher with the same variation of the original coefficient. By increasing the repulsive coefficient, the liquid particle number density, or the cutoff radius, the viscosity of the T-MDPD fluid is enhanced as well. Based on this extension of the MDPD scheme, a quantitative expression for the variation of the viscosity in the current T-MDPD fluid is derived. In future simulations of multiphase flows using an MDPD scheme, the transverse effect can be extended to effectively tune the viscosity, and this empirical expression will be useful to predict the viscosity of the T-MDPD fluid.