Abstract: An introduction is given to the γ-Re_θ transition model based on local variables. Through the control of the free flow turbulence attenuation by Spalart’s ambient source term method, a practical transition model is achieved. Based on the transition model developed in software TRIP of China Aerodynamics Research and Development Center, the flow over low speed airfoils, including airfoil S809, NLR7301 and airfoil 30P30N, is studied. Numerical simulations and comparisons of their dynamic characteristics indicate that the transition locations of natural transition and separated transition accord with the experimental data; the relaminarization of turbulent flow along the pressure gradient zone is well simulated, and the aerodynamic simulation accuracy is effectively increased. This model may find wide application in engineering; and the correctness of the γ-Re_θ transition model in software TRIP of CARDC is validated. The calculated results also indicate that while the Re number in the laminar flow corresponds to that in the turbulent flow, only the transition model can improve the precision of calculated aerodynamics.

Key words: boundary layer, laminar to turbulent transition, turbulence intensity, flow simulation, intermittency, low speed airfoil