Pressure safety valve

IUTDavood · August 8, 2015, 05:02

Hi all,

I'm solving a Pressure safety valve by Rigid body method with Ideal gas in CFX but I have one problem:
1. By using the inlet total pressure, the Run Error is: "100% inlet blocked", and the run will be iterated so the results will not be correct.
2. By using the inlet Mass flow, the Run Error is:"Over flow" and the run will be stopped.
3. By using the inlet static pressure, the Run will not be any Error but the results will not be correct.
The conditions are: Pin=6bar, Pout=atm (opening), Ideal gas mass flow is available for validation, Tur. model= SST and 2D geometry.
According to the mentioned post by others I has performed all options for Run and converging (such as: I used local time scale for Over flow error but other Error "the local time scale for rigid body not available" appeared. and ...
The Chock problem is the main reason of diverging and mentioned errors.
Anyway for Run and Converging issue, are there any offer?

Thanks,

fresty · August 8, 2015, 15:37

Have you tried using density as a function of pressure.. usually slightly compressible behavior is encountered & is advisable to be modeled for valve simulations (density as a function of pressure differential and bulk modulus of fluid involved) due to potential cavitation or pulsations.. i would probably suggest to stick with your '2.' boundary conditions and use density model as a function of changing pressure (using a CEL)..

IUTDavood · August 10, 2015, 10:51

Many thanks,
By using the ideal gas in cfx, that variation of density by pressure will be occurred, are there other offer?

IUTDavood · August 10, 2015, 12:14

The problem was solved.

fresty · August 10, 2015, 13:27

Quote:

Originally Posted by IUTDavood

Many thanks,
By using the ideal gas in cfx, that variation of density by pressure will be occurred, are there other offer?

Yes, i guess that's right.. sorry missed that part .. it would be catered already..

August 8, 2015, 05:02	Pressure safety valve	#1
IUTDavood New Member Davood Join Date: Aug 2015 Posts: 5 Rep Power: 11	Hi all, I'm solving a Pressure safety valve by Rigid body method with Ideal gas in CFX but I have one problem: 1. By using the inlet total pressure, the Run Error is: "100% inlet blocked", and the run will be iterated so the results will not be correct. 2. By using the inlet Mass flow, the Run Error is:"Over flow" and the run will be stopped. 3. By using the inlet static pressure, the Run will not be any Error but the results will not be correct. The conditions are: Pin=6bar, Pout=atm (opening), Ideal gas mass flow is available for validation, Tur. model= SST and 2D geometry. According to the mentioned post by others I has performed all options for Run and converging (such as: I used local time scale for Over flow error but other Error "the local time scale for rigid body not available" appeared. and ... The Chock problem is the main reason of diverging and mentioned errors. Anyway for Run and Converging issue, are there any offer? Thanks, Last edited by IUTDavood; August 8, 2015 at 06:00. Reason: Chock

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August 8, 2015, 15:37		#2
fresty Senior Member Join Date: Aug 2014 Location: UK Posts: 213 Rep Power: 13	Have you tried using density as a function of pressure.. usually slightly compressible behavior is encountered & is advisable to be modeled for valve simulations (density as a function of pressure differential and bulk modulus of fluid involved) due to potential cavitation or pulsations.. i would probably suggest to stick with your '2.' boundary conditions and use density model as a function of changing pressure (using a CEL)..

August 10, 2015, 10:51		#3
IUTDavood New Member Davood Join Date: Aug 2015 Posts: 5 Rep Power: 11	Many thanks, By using the ideal gas in cfx, that variation of density by pressure will be occurred, are there other offer?

August 10, 2015, 12:14		#4
IUTDavood New Member Davood Join Date: Aug 2015 Posts: 5 Rep Power: 11	The problem was solved.