Abstract: According to the equal flow shear stress at the interface in adjacent finite volumes, the traditional finite volume method (FVM) is improved in consideration of the viscosity variation in adjacent finite volumes. The new discretization and computing formulae concerning velocity gradient at the center of finite volume, as well as velocity and its gradient at the interface are deduced for the improved FVM. The new discretization and computing formulae are apt to the situation that melt viscosity varies very quickly during the filling stage of plastic injection molding. The improved FVM can avoid steep oscillation of flow shear stress in adjacent finite volume. Similarly, according to equal heat flux at the interface in adjacent finite volumes, the new discretization and computing formulae of temperature gradient are also deduced when the changing of heat conductivity coefficient in adjacent finite volumes is taken into account. Thus the improved FVM results in numerical stability and accuracy in the simulation of filling stage. The presented approach is used to simulate the steady laminar flow in a cylinder and the filling stage of a box, a plate with concave groove and a plastic part with general 3D features. The simulation results agreed well with the theoretic solution, experimental data and those from commercial software respectively. So the improved approach is verified to be able to exactly simulate the filling stage of plastic injection molding. In practice, it can also be theoretically applied in the coupled simulation of other single fluid or multi fluid.

Key words: filling, improved finite volume method, numerical simulation, plastic injection molding, viscosity