Nozzle with a narrow neck
 

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!

Re: Nozzle with a narrow neck
 

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???

Re: Nozzle with a narrow neck
 

Hi Jenny,

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

-->Solve-->Controls-->Limits

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

Mark