Abstract: The basic concept of mixed method is to split the original set of equations into a Part Differential Equation (PDE) for the convection-diffusion part, and an Ordinary Differential Equation (ODE) for the source term. The PDE is solved by a conventional numerical method, while the ODE is integrated analytically. It is shown that the mixed method improves the accuracy of source term numerical treatment, and is much more accurate than the traditional method. For the two equations turbulence model, the mixed method without time splitting is developed, which allows for convergence to steady state. The application of mixed method on turbulent flow simulation is studied. Numerical result shows that the mixed analytical/numerical method is much better that the conventional method. The mixed method improves the numerical stability, and accelerates the convergence.

Key words: CFD, mixed analytical/numerical method, k-ε turbulence model, source term, steady state, stiffness