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Old   February 3, 2005, 14:50
Default Nozzle with a narrow neck
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I am modeling a nozzle with a narrow neck. The inlet pressure is about 3000 psi(about 206 ATM) and the temperature is about 1000 F. The outlet BC is pressure-outlet. Whatever I set the inlet BC as mass-flow-rate-inlet, pressure-inlet or velocity-inlet, it always diverge. I have a fine 2D mesh, about 98,000 elements. I don't know where the problem is. Hope someone can help me with this headache.

Thanks a lot!
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Old   February 3, 2005, 14:54
Default Re: Nozzle with a narrow neck
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When I run the program, it always says: absolute pressure limited to 1.000000e+00 in 6581 cells on zone 2 absolute pressure limited to 5.000000e+06 in 1778 cells on zone 2 turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 8807 cells temperature limited to 1.000000e+00 in 16 cells on zone 2 in domain 1 temperature limited to 5.000000e+03 in 56 cells on zone 2 in domain 1

What does these warnings mean? It means my pressure and temperature are so high???
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Old   February 4, 2005, 05:31
Default Re: Nozzle with a narrow neck
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Hi Jenny,

You're exceeding the default limits set in the solver. You can alter these values via the following GUI menus,


You will definitely need to increase the upper limit for absolute pressure (default 5e+6Pa) since your inlet BC is 2.1e+7Pa. Try using a value of 1.0e+8Pa and re-run the model.

Also, how are you initialising yor model? You may have to use different initial conditions to get the model started.

Good Luck

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