VF Phase does not converge

nashim.chowdhury · April 21, 2017, 22:15

Hi, I am modelling cavitation in a t-junction pipe. All of my residuals converge apart from the vf phase which plateaus.

Why does it not converge?

EDIT: could it be due to that fact I am running this as steady ?

sina_mech · April 24, 2017, 03:44

Something that you should find out, before looking in other details, is that whether your problem has steady state solution or not. For example, filling a tank has no steady state solution, and water flow in a tank with an outlet might have a SS solution. I don't know your problem's details, but I don't think it has a SS solution.

Then, I would make sure I have correct boundary conditions, and initial condition (correct patching of the domain if needed for the second phase). Try to reduce the volume fraction under-relaxation factor to something around 0.25, and see if you notice a change or not.

nashim.chowdhury · April 24, 2017, 05:29

Hi, yes it does converge when ran transiently, agreed, this system is not in a steady state.
Thank you for the response

April 21, 2017, 22:15	VF Phase does not converge	#1
nashim.chowdhury New Member nashim Join Date: Feb 2017 Posts: 9 Rep Power: 9	Hi, I am modelling cavitation in a t-junction pipe. All of my residuals converge apart from the vf phase which plateaus. Why does it not converge? EDIT: could it be due to that fact I am running this as steady ?

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April 24, 2017, 03:44		#2
sina_mech Senior Member SinaJ Join Date: Nov 2009 Posts: 136 Rep Power: 17	Something that you should find out, before looking in other details, is that whether your problem has steady state solution or not. For example, filling a tank has no steady state solution, and water flow in a tank with an outlet might have a SS solution. I don't know your problem's details, but I don't think it has a SS solution. Then, I would make sure I have correct boundary conditions, and initial condition (correct patching of the domain if needed for the second phase). Try to reduce the volume fraction under-relaxation factor to something around 0.25, and see if you notice a change or not.

April 24, 2017, 05:29		#3
nashim.chowdhury New Member nashim Join Date: Feb 2017 Posts: 9 Rep Power: 9	Hi, yes it does converge when ran transiently, agreed, this system is not in a steady state. Thank you for the response