Rheology of polymers in many-body dissipative particle dynamics simulations: Schmidt number effect

Abstract

The Schmidt number effect on the rheology of finitely extensible nonlinear elastic chains (FENE) in many-body dissipative particle dynamics (MDPD) is investigated in this work. We find that the Schmidt number, ranging from (101) to (103), has limited influence on the polymer properties, such as its radius of gyration (Rg), diffusion coefficient (D) and relaxation time (τ). The simulation results follow Zimm model's predictions well. The hydrodynamic interaction strength parameter h* demonstrates that the full hydrodynamic interaction can be simulated for Schmidt number from (100-106) in MDPD. Next, the rheology of FENE polymers is studied using Lees-Edward boundary condition in shear flow. The shear-thinning and normal stress difference are measured and analysed with MDPD; meanwhile, the volume fraction, solvent quality and chain length are varied to explore their effects on the extent of the Newtonian region. Finally, the non-Newtonian droplet is firstly simulated in MDPD. Its maximum spreading diameter is measured for both Newtonian and non-Newtonian droplet with Weber number (We) ranging from 4.37 to 109.2 on hydrophilic, moderate and hydrophobic surfaces, respectively. The fluid shear-thinning property increases at high shear rate and is further enhanced on more hydrophobic surface, from the maximum spreading diameter results. The non-Newtonian (FENE) droplet can be now well simulated in MDPD and this provides additional insight to further research concerning polymer-solvent-surface interactions, which is crucial in various applications.