Abstract: On the basis of the engineering background of advanced polymer multi-component molding techniques, the fully three-dimensional unsteady non-isothermal theoretical model of multiphase-multilayer cavity filling flow is established. Con-sidering the main reasons of numerical unsteady and diffusion in solution of the theoretical model，the corresponding Stabled numerical algorithm with fast convergence is put forward. The numerical algorithm decreases the needs of the computer CPU and memory capacity by means of penalty function method and uncoupling solution of velocity field, temperature field and fraction of fluid volume. A stabled finite element analysis is implemented by SUPG method (Streamline upwind /Petrov- Galerkin method), penalty function method and P1+/P1 three-dimensional finite element etc. On the base of penalty function method and SUPG method, the fully three-dimension finite element numerical model of solving N-S equation, energy equation and the tracing equation of moving front interface and stratified interface is deduced, and reconstruction technique of moving front interface and stratified interface is discussed in fully three-dimensional unsteady non-isotherma multiphase-mu-ltilayer flow. The initiating mechanisms of viscous encapsulation and interface instability are finally disclosured by numerical modeling technology.

Key words: Interface instability, Multi-component molding, Multiphase-multilayer flow, Numerical simulation, Viscous encapsulation