Abstract: The Navier-Stokes(NS)method is coupled with the direct simulation Monte Carlo(DSMC) method to calculate the transition flow. The feedback mechanism of the two-way coupling method is realized by using the method of mutually modifying the boundary value of NS and DSMC， which is very important for non-steady state research and numerical correction. The results show that the two-way coupling results are highly similar to the global DSMC results， and have higher efficiency， stability， and accuracy than the one-way coupling. Improving the coupling frequency can improve stability and accuracy. The two-way coupling obtains higher subdomain convergence， stability， and accuracy by using the boundary value of global NS results. The foresight algorithm can enhance the time coupling of the DSMC domain and lay the foundation for non-steady state calculations.

Key words: NS/DSMC method; two-way coupling; transition flow; foresight algorithm; PECVD (plasma enhanced chemical vapor deposition)