This paper presented the numerical investigation reports about the performance of transonic wind tunnel's second throat.Firstly

second throats were designed according to the general design rule.Then exact Mach number control was studied by numerical simulation when different second throat areas were analyzed by adjusting wall flaps and center body.The numerical results indicate that the control precision of Mach number is 0.001.At last

different models were studied based on the numerical results

and then the most efficient model was selected.