Two Phase Flow In Vertical Pipe

stonepreston · October 29, 2017, 15:54

I am trying to model a two phase flow in a vertical pipe using a boiling model.
I used the 2nd part of this tutorial to guide my process.

The problem I am trying to model is given below:
A vertical steel tube carries water at a pressure of 10 bars. Saturated liquid water is pumped into the D = 0.1 m diameter tube at its bottom end (x = 0) with a mean velocity of um= 0.05 m/s. The tube is exposed to combusting pulverized coal, providing a uniform heat flux of q” = 100,000 W/m2. The total length of the pipe is 30 meters.

A small piece of my mesh is shown here:
https://imgur.com/a/fT73G

I followed the tutorial to setup the eulerian boilding mode. I copied the liquid water and water vapor materials from the fluent database, setup the two phases, and specified the phase interactions. I made sure to change the saturation temperature in the boiling mass transfer mechanism to the saturation temperature at 10 bar.

I specified the inlet velocity as .05 m/s for the liquid phase, and 0 for the vapor phase (since its a saturated liquid at the inlet). I also specified a gage pressure of 1000000 at the inlet for the mixture and 0 pressure at the outlet for the mixture.

When I try to initialize, I get the following error:

Code:

Initialize using the hybrid initialization method.

Checking case topology... 
-This case has both inlets & outlets 
-Pressure information is not available at the boundaries.
 Case will be initialized with constant pressure

	iter		scalar-0

	1		0.000000e+00
	2		0.000000e+00
	3		0.000000e+00
	4		0.000000e+00
	5		0.000000e+00
	6		0.000000e+00
	7		0.000000e+00
	8		0.000000e+00
	9		0.000000e+00
	10		0.000000e+00
hybrid initialization is done.
# Divergence detected in AMG for ads-0: protective actions enabled!
# Divergence detected in AMG for ads-0, temporarily solve with BCGSTAB!

Divergence detected in AMG solver: ads-0# Divergence detected in AMG for ads-0: protective actions enabled!
# Divergence detected in AMG for ads-0, temporarily solve with BCGSTAB!

Divergence detected in AMG solver: ads-0# Divergence detected in AMG for ads-0: protective actions enabled!
# Divergence detected in AMG for ads-0, temporarily solve with BCGSTAB!

Divergence detected in AMG solver: ads-0# Divergence detected in AMG for ads-0: protective actions enabled!
# Divergence detected in AMG for ads-0, temporarily solve with BCGSTAB!

Divergence detected in AMG solver: ads-0# Divergence detected in AMG for ads-0: protective actions enabled!
# Divergence detected in AMG for ads-0, temporarily solve with BCGSTAB!

Divergence detected in AMG solver: ads-0# Divergence detected in AMG for ads-0: protective actions enabled!
# Divergence detected in AMG for ads-0, temporarily solve with BCGSTAB!

Divergence detected in AMG solver: ads-0# Divergence detected in AMG for ads-0: protective actions enabled!
# Divergence detected in AMG for ads-0, temporarily solve with BCGSTAB!

Divergence detected in AMG solver: ads-0# Divergence detected in AMG for ads-0: protective actions enabled!
# Divergence detected in AMG for ads-0, temporarily solve with BCGSTAB!

Divergence detected in AMG solver: ads-0# Divergence detected in AMG for ads-0: protective actions enabled!
# Divergence detected in AMG for ads-0, temporarily solve with BCGSTAB!

Divergence detected in AMG solver: ads-0# Divergence detected in AMG for ads-0: protective actions enabled!
# Divergence detected in AMG for ads-0, temporarily solve with BCGSTAB!

Divergence detected in AMG solver: ads-0
Error at host: floating point exception

Error at Node 0: floating point exception

Error: floating point exception
Error Object: #f

How can I resolve this error? Is the problem with my mesh?

Here is my mesh check:

Code:

 Domain Extents:
   x-coordinate: min (m) = 2.078713e-01, max (m) = 2.578713e-01
   y-coordinate: min (m) = 0.000000e+00, max (m) = 3.000000e+01
 Volume statistics:
   minimum volume (m3): 1.320992e-07
   maximum volume (m3): 7.924628e-03
     total volume (m3): 1.413717e+02
   minimum 2d volume (m3): 4.204847e-06
   maximum 2d volume (m3): 4.204847e-05
 Face area statistics:
   minimum face area (m2): 4.204847e-04
   maximum face area (m2): 1.000000e-02
 Checking mesh............................
Done.

and my mesh quality:

Code:

Mesh Quality:

Minimum Orthogonal Quality =  1.00000e+00
(To improve Orthogonal quality , use "Inverse Orthogonal Quality" in Fluent Meshing,
 where Inverse Orthogonal Quality = 1 - Orthogonal Quality)

Maximum Aspect Ratio =  2.38031e+01

stonepreston · October 30, 2017, 17:38

anyone have any ideas? Could really use some help/input

litzj · October 31, 2017, 09:35

I cannot check your *.cas file, then I couldn't convince that

when there is a problem in initialization process, it might be problem in

B.C set up...

or How about using standard initialization rather than hybrid one?

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October 30, 2017, 17:38		#2
stonepreston New Member Stone preston Join Date: Oct 2017 Posts: 7 Rep Power: 9	anyone have any ideas? Could really use some help/input

October 31, 2017, 09:35		#3
litzj Member Jaesan Yoon Join Date: Sep 2017 Posts: 36 Rep Power: 9	I cannot check your *.cas file, then I couldn't convince that when there is a problem in initialization process, it might be problem in B.C set up... or How about using standard initialization rather than hybrid one?