Numerical Simulations Of Polymeric Fluid Flow Based On Dissipative Particle Dynamics

With the development of computer technology,numerical simulation has been widely used in various fields.The numerical simulation of flow is an effective method to solve the problem of complex flow.Macroscopic computational fluid dynamics(CFD)and microscopic molecular dynamics(MD)methods have been promoted in the numerical simulation of fluid flow.The scale of mesoscopic simulation methods is between macroscopic scale and microscale.Mesoscopic simulation is useful for the problem of flow which is not suitable for the continuum theory compared with the macro simulation.Mesoscopic simulation also has much larger scale of the calculation and higher efficiency than the microscale simulation.For the study of high relative molecular weight of polymer fluid,Mesoscopic simulation has good adaptability.Polymeric fluid include polymer melt and polymer solution,which is complex fluid with rheological properties.In this paper,polymeric fluid is chosen as the object of study and be simulated by one of the mesoscopic simulation method DPD for the flow property of polymeric fluid.The main work of this paper is as follows:.Dissipative particle dynamics method is used to simulate the Couette flow and Poiseuille flow with Newtonian fluid and acquire the velociety and shear stress distribution.Compared with the exact solution of theory analysis,we validate the algorithm and coefficient and it lays the foundation for the flow simulation of polymer fluid.The parallel computation of the dissipative particle dynamics method is studied,and the feasibility of parallel computing is verified by comparing the parallel computing results of the nodes of different number of processors.The speedup and parallel efficiency of parallel computing are obtained,and the influence of processor grid arrangement on parallel efficiency is also studied.Dissipative particle dynamics is used to simulate the flow behavior of polymer melt and polymer solution.First,the flow behavior of polymer fluid under simple shear is simulated.In the simulation,the method of Lees-Edwards boundary treatment is used to replace the traditional method of frozening wall particles.The velocity distribution and shear stress distribution of different types of polymer fluid are solved.The rheological properties of the shear thinning of the polymer fluid are studied by the relationship between the viscosity and the shear rate.Then,the reverse Poiseuille flow model is used to simulate the flow of polymer melt,and the power law model is used to characterize the rheological behavior of polymer melt.Finally,the flow properties of polymer solution are numerically simulated by the reverse Poiseuille flow model.The factors affecting the distribution of polymer chains and the velocity distribution of polymer solution in the passage channel were investigated from four aspects: the size of the driving force,the length of the polymer chains,the mass of the solvent and the concentration of polymer.Compared with the conventional frozening wall particles boundary method of Couette flow and Poiseuille flow numerical simulation,the LeesEdwards boundary conditions and the reversed Poiseuille flow phase have achieved the implementation of the periodic boundary,which can eliminate the influence of the near wall particle fluctuation on the simulation results.