Help with "AMG divergence: Temperature" for choke flow simulation

Leviro91 · February 17, 2016, 01:26

I am currently doing my final year project for undergrad involving cfd simulation for the erosion of a choke. Hence, I apologize beforehand if my question is too basic.

The material is a species mixture comprising of mainly methane together with nitrogen, CO2 etc. I run it with a volume weighted average density method in order to run without the energy equation. It works fine. However, after changing the density method to incompressible ideal gas, the solver gives me a temperature divergence error after about 50 iterations.

May I ask what are the likely causes for this error in the context of this problem? Thank You.

adrin · February 17, 2016, 05:01

You don't say much about the physics of the problem (say, what's the max Mach number, temperature, etc). I would nevertheless venture to guess that your problem is to assume incompressible flow for gases (which are quite likely compressible)

adrin

Leviro91 · February 17, 2016, 12:25

Thnks Adrin! I will try to run it as a compressible flow to see if it solves the problem. I initially ran it as an incompressible flow to compare the differences between compressible and incompressible flow models (That's the essence of my project).

Judging from the initial run with energy off, I would say the max Mach number is ~0.6, which I am aware is in the region where it should be considered as a compressible flow. The temperature at the inlet is 334K. The turbulence model used is the k-epsilon model with enhanced wall treatment.

February 17, 2016, 01:26	Help with "AMG divergence: Temperature" for choke flow simulation	#1
Leviro91 New Member Jet Join Date: Feb 2016 Posts: 2 Rep Power: 0	I am currently doing my final year project for undergrad involving cfd simulation for the erosion of a choke. Hence, I apologize beforehand if my question is too basic. The material is a species mixture comprising of mainly methane together with nitrogen, CO2 etc. I run it with a volume weighted average density method in order to run without the energy equation. It works fine. However, after changing the density method to incompressible ideal gas, the solver gives me a temperature divergence error after about 50 iterations. May I ask what are the likely causes for this error in the context of this problem? Thank You.

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February 17, 2016, 05:01		#2
adrin Senior Member adrin Join Date: Mar 2009 Posts: 115 Rep Power: 17	You don't say much about the physics of the problem (say, what's the max Mach number, temperature, etc). I would nevertheless venture to guess that your problem is to assume incompressible flow for gases (which are quite likely compressible) adrin

February 17, 2016, 12:25		#3
Leviro91 New Member Jet Join Date: Feb 2016 Posts: 2 Rep Power: 0	Thnks Adrin! I will try to run it as a compressible flow to see if it solves the problem. I initially ran it as an incompressible flow to compare the differences between compressible and incompressible flow models (That's the essence of my project). Judging from the initial run with energy off, I would say the max Mach number is ~0.6, which I am aware is in the region where it should be considered as a compressible flow. The temperature at the inlet is 334K. The turbulence model used is the k-epsilon model with enhanced wall treatment.