The numerical simulation is carried out entirely on the computer, which can greatly reduce the research and development cost compared with the traditional test method. But the accuracy of CFD numerical simulation results depends on many aspects, such as the accuracy of the geometric model of network quality, selection of calculation model, the convergence of numerical calculation, etc., so the CFD numerical simulation method cannot completely replace the test method, on the contrary by the results of trial calculation model can be set in the selection of the parameters modification so as to further perfect model