FSI - Gridflux Problem

mwe · April 7, 2014, 06:20

Hello,

I'm quite new to CFD and I'm trying to simulate the following problem:

A phase change material encapsulated in a plastic tube that is heated from an inner tube filled with water. So from the inner axis it's basically: water - coppertube-pcm-plastic tube.

I was able to resolve my previous issue, but no it seems I'm not able to get convergence in the mechanical part of the simulation (basically my mesh "explodes" because my forces become unreasonably high).

I get this error message multiple times before the mesh looses quality beyond usability: "pressure corrections limited on 446472 cells in pcm"

I hope someone might have an idea to solve this problem? (Thanks in advance for any tips

)

Software is StarCCM+ v8

me3840 · April 7, 2014, 13:20

I don't see how this is FSI, it sounds just like CHT.

mwe · April 8, 2014, 02:21

The phase change material reduces density when going from solid to liquid causing the tube to expand (it's designed to do that).

me3840 · April 8, 2014, 09:43

Have you done the analysis with just CHT to see if it converges?

mwe · May 7, 2014, 07:34

Yes, with fixed walls and no mechanical stress the simulation converges.

April 7, 2014, 06:20	FSI - No Convergence	#1
mwe New Member Join Date: Apr 2014 Posts: 9 Rep Power: 12	Hello, I'm quite new to CFD and I'm trying to simulate the following problem: A phase change material encapsulated in a plastic tube that is heated from an inner tube filled with water. So from the inner axis it's basically: water - coppertube-pcm-plastic tube. I was able to resolve my previous issue, but no it seems I'm not able to get convergence in the mechanical part of the simulation (basically my mesh "explodes" because my forces become unreasonably high). I get this error message multiple times before the mesh looses quality beyond usability: "pressure corrections limited on 446472 cells in pcm" I hope someone might have an idea to solve this problem? (Thanks in advance for any tips ) Software is StarCCM+ v8 Last edited by mwe; April 7, 2014 at 10:34.

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April 7, 2014, 13:20		#2
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 24	I don't see how this is FSI, it sounds just like CHT.

April 8, 2014, 02:21		#3
mwe New Member Join Date: Apr 2014 Posts: 9 Rep Power: 12	The phase change material reduces density when going from solid to liquid causing the tube to expand (it's designed to do that).

April 8, 2014, 09:43		#4
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 24	Have you done the analysis with just CHT to see if it converges?

May 7, 2014, 07:34		#5
mwe New Member Join Date: Apr 2014 Posts: 9 Rep Power: 12	Yes, with fixed walls and no mechanical stress the simulation converges.