I am a new user of CFX program. I was testing a subsonic-supersonic nozzle, with this characteristics: inlet: stagnation temperature 300K and stagnation pressure 10 atm (absolute) and outlet: supersonic. Using air (ideal gas model). Because I get incorrect answers? ps. The mack number in through are not one! Thanks

First use an pressure outlet with a lower than critical ratio with the inlet pressure. Your supersonic flow will develop then. Starting with a supersonic outlet with automatic startup is not good as the initial velocity is probably subsonic.