Simulation Of Polymer Fluid Under Microscale And Mesoscale

Viscosity is one of the most important characteristics of the polymer fluids, and it is also a key influence factor of polymer material processing.Getting the constitutive equation that reveals material property has become the key to caryy out polymer processing simulation with traditional finite element simulation. It has become an important reserch direction to obtain the stress-strain relationship of complex fluid under certain conditions through the microscopic simulation or mesoscopic simulation method, so as to avoid the constitutive equation.The simulation of polymer fluid is often difficult to achieve only through single scaling simulation,due to its long chains of chain structure and big scale span.In this paper,we conduct a nonequilibrium simulation about polymer fluid through a connection of microscale molecular dynamic simulation and mesoscale dissipative particle dynamics simulation.And we focus on the viscosity in our simulation mold. The main work in this paper are as follows:1) We set up the molecular simulation model of polyethylene, and implement the molecular dynamics simulation with the software lammps. Structure information, thennodynamic properties, and transport properties are analyzed in detail under the condition of450K,1atm,with the system of96PE chains,one of which contain96union atoms. The radial distribution function, mean square rotary radius, density, and orientation of polyethylene are used to characterize the model.2) Through the method that based on the radial distribution function,we set up DPD simulation of conservative potential energy, and realizes the connection between molecular dynamics simulation and dissipation particle dynamics simulation. Several key parameters have been investigate to obtain the proper simulation parameters through comparing with the result of MD simulation.3) We set up two kinds of different models of polymer fluid flow, and calculated the velocity distribution, shear stress distribution and shear viscosity in the process of flow, then the result with the simulation are compared with results of the theoretical analysis, which show that both of the models indicate the same variation tendency in velocity distribution and stress distribution.