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david
Posts: 2
Registered: ‎08-08-2013
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Unphysical results during nozzle simulation

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08-14-2013 02:46 AM

I've recently been trying to simulate flow in a small rocket nozzle. However, the results i get from the simulations shows some very weird results, such as static pressures maxing out far above any of the boundary condition pressures and apparent flow through edges that i thought should behave as adiabatic walls.

 

I probably made some sort of mistake during setup of the simulation, but I can't figure out what it is. Does somebody know what can cause this kind of behaviour?

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Royce_adsk
Posts: 617
Registered: ‎08-24-2011

Re: Unphysical results during nozzle simulation

08-15-2013 12:47 PM in reply to: david

Hi David,

 

Modeling a compressible flow problem with just a total pressure at the inlet and unknown at the outlet isn't enough.

 

Review the suggested guidelines here:

http://wikihelp.autodesk.com/Simulation_CFD/enu/2013/Help/0407-Learning407/0726-Guidelin726/0761-Com...

 

Other issues you do have:

1) Need Variable Air properties .. right click on change the env. reference to variable instead of fixed

2) Many Compressible problems solve much too fast and diverge with default settings. There are many ways to control this, but one of the easiest ways is to modify the turb/lam ratio.  I bumped your up to 2000 after adjust for step 1 and it does run.

3) Use ADV5 instead of ADV2.  ADV5 is newer and solves compressible problems very well.

 

Best regards,



Royce Abel
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New Member
david
Posts: 2
Registered: ‎08-08-2013

Re: Unphysical results during nozzle simulation

08-16-2013 07:12 AM in reply to: Royce_adsk

Thanks for the explanation, especially the one about turb/lam ratio is good to know.

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