Propeller cavitation with non condensable gas(first constant property then ideal gas)

CFD-fellow · February 9, 2015, 05:47

Hi
Im modeling cavitation on a propeller with a constant volume fraction of air.After a procedure I got converged solution with reasonable results.
Now when I change air to ideal gas (with isothermal heat transfer) or define an expression for variable density with the previous run as initial value, I get overflow error on the first time step.
B.C:velocity inlet and opening with static pressure.
tstep=0.0001

Ive also decreased time step to 10e-9 which didnt help.
Decreasing relaxation factors caused overflow happen later(on 6th tstep)
Any idea?

ghorrocks · February 9, 2015, 06:23

I have attempted a similar simulation previously and never got it to work either. I never looked into it very hard, but you can expect to have a hard time getting this to converge (as you have found). I can only recommend trying some of the solver expert parameters and other solver settings and see if they help, otherwise contact ANSYS and see if they can help you.

February 9, 2015, 05:47	Propeller cavitation with non condensable gas(first constant property then ideal gas)	#1
CFD-fellow Senior Member Behrooz Jamshidi Join Date: Apr 2013 Posts: 110 Rep Power: 14	Hi Im modeling cavitation on a propeller with a constant volume fraction of air.After a procedure I got converged solution with reasonable results. Now when I change air to ideal gas (with isothermal heat transfer) or define an expression for variable density with the previous run as initial value, I get overflow error on the first time step. B.C:velocity inlet and opening with static pressure. tstep=0.0001 Ive also decreased time step to 10e-9 which didnt help. Decreasing relaxation factors caused overflow happen later(on 6th tstep) Any idea?

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February 9, 2015, 06:23		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 18,017 Rep Power: 146	I have attempted a similar simulation previously and never got it to work either. I never looked into it very hard, but you can expect to have a hard time getting this to converge (as you have found). I can only recommend trying some of the solver expert parameters and other solver settings and see if they help, otherwise contact ANSYS and see if they can help you.