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-   -   Nozzle - Simulation converges, but data incorrect (http://www.cfd-online.com/Forums/cfx/66604-nozzle-simulation-converges-but-data-incorrect.html)

fade July 20, 2009 04:13

Nozzle - Simulation converges, but data incorrect
 
Hello,

I'm running a simulation on a laval converging-diverging nozzle, and while the answer is converging, the values are lower than what Fluent gave (a program I don't currently have access to, which is why I am using CFX, which I am less familiar with), or what experiments show. The problem is set using the energy equation, with a pressure inlet and supersonic outlet. The residuals are good, and the flow profile makes sense, but the velocities are about 20% low.
Because of the high pressure (~40 atm), I started with lower pressures and a subsonic outlet, and built up the speed slowly. In searching results, most people seem to have trouble with convergence, which I did not, but if anyone has any idea why the values are unusual, they would be much appreciated.

thanks,
-john


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