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Rocket Engine Starting/Stopping Simulation

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Old   September 30, 2012, 10:27
Default Rocket Engine Starting/Stopping Simulation
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Hello!

I need to simulate a flow in CD nozzle where pressure and temperature at inlet changes from 0 to some level and then from this level to 0. Is it possible to simulate such a process it CFX? If possible, then what kind of boundary conditions at outlet and relative pressure should I specify?
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Old   October 1, 2012, 07:30
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Glenn Horrocks
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CFX cannot model plasmas or explosions, but has a chemistry model. It also has all the normal Navier Stokes solver stuff like compressible flow, heat transfer etc.

So if your flow can be described with a chemistry model then probably yes. But if you need plasma or explosion models then no.
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Old   October 22, 2012, 05:16
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Quote:
Originally Posted by ghorrocks View Post
CFX cannot model plasmas or explosions, but has a chemistry model. It also has all the normal Navier Stokes solver stuff like compressible flow, heat transfer etc.

So if your flow can be described with a chemistry model then probably yes. But if you need plasma or explosion models then no.
I don't need to model plasma and reactions. All I need is to model transient flow in CD nozzle where chamber pressure changes from 0 to 7 atm (nozzle start) and then from 7 atm to 0 (nozzle shut down). Outside pressure is 0 (vacuum). Since outlet velocity changes from subsonic to supersonic and vice versa, what BC should I specify there? I tried to specify opening and outlet with pressure 0 and near 0 (taking into account the Reference Pressure). As the Ref. Pressure I tried to specify 7 atm and 0. CFX failed in both cases.
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Old   October 23, 2012, 16:59
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CFX cant handle mixed BCs like this at the outlet. Try modeling more of the domain in the nozzle exit region in order to get a fully subsonic exit, regardless of time during the transient.
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