Fatal Error: Unphysical field variables detected

MFiX
#1

Hi everyone,

I modified the tutorial 2-d pseudo spouted bed by adding chemical reaction and changing the inlet air to 300 centigrade. The solver is built successfully but an error showed:

ERROR check_data_30.f:670
Fatal Error: Unphysical field variables detected.
I J K
6 39 16 T_G = 250.0 <= 250.0
6 40 16 T_G = 250.0 <= 250.0
6 41 16 T_G = 250.0 <= 250.0
6 42 16 T_G = 250.0 <= 250.0
6 39 17 T_G = 250.0 <= 250.0
6 40 17 T_G = 250.0 <= 250.0
6 41 17 T_G = 250.0 <= 250.0
6 42 17 T_G = 250.0 <= 250.0
2 32 18 T_G = 250.0 <= 250.0
2 33 18 T_G = 250.0 <= 250.0
2 34 18 T_G = 250.0 <= 250.0
2 35 18 T_G = 250.0 <= 250.0
2 36 18 T_G = 250.0 <= 250.0
2 37 18 T_G = 250.0 <= 250.0
2 38 18 T_G = 250.0 <= 250.0
6 38 18 T_G = 250.0 <= 250.0
2 39 18 T_G = 250.0 <= 250.0
6 39 18 T_G = 250.0 <= 250.0
2 40 18 T_G = 250.0 <= 250.0
6 40 18 T_G = 250.0 <= 250.0
2 41 18 T_G = 250.0 <= 250.0
6 41 18 T_G = 250.0 <= 250.0
2 42 18 T_G = 250.0 <= 250.0
6 42 18 T_G = 250.0 <= 250.0
2 31 19 T_G = 250.0 <= 250.0
2 32 19 T_G = 250.0 <= 250.0
2 33 19 T_G = 250.0 <= 250.0
2 34 19 T_G = 250.0 <= 250.0
2 35 19 T_G = 250.0 <= 250.0
6 35 19 T_G = 250.0 <= 250.0
2 36 19 T_G = 250.0 <= 250.0
6 36 19 T_G = 250.0 <= 250.0
2 37 19 T_G = 250.0 <= 250.0
6 37 19 T_G = 250.0 <= 250.0
2 38 19 T_G = 250.0 <= 250.0
6 38 19 T_G = 250.0 <= 250.0
2 39 19 T_G = 250.0 <= 250.0
6 39 19 T_G = 250.0 <= 250.0
2 40 19 T_G = 250.0 <= 250.0
6 40 19 T_G = 250.0 <= 250.0
2 41 19 T_G = 250.0 <= 250.0
6 41 19 T_G = 250.0 <= 250.0
2 42 19 T_G = 250.0 <= 250.0
6 42 19 T_G = 250.0 <= 250.0
2 30 20 T_G = 250.0 <= 250.0
2 31 20 T_G = 250.0 <= 250.0
2 32 20 T_G = 250.0 <= 250.0
2 33 20 T_G = 250.0 <= 250.0
2 34 20 T_G = 250.0 <= 250.0
2 35 20 T_G = 250.0 <= 250.0
6 35 20 T_G = 250.0 <= 250.0
2 36 20 T_G = 250.0 <= 250.0
6 36 20 T_G = 250.0 <= 250.0
2 37 20 T_G = 250.0 <= 250.0
6 37 20 T_G = 250.0 <= 250.0
2 38 20 T_G = 250.0 <= 250.0
6 38 20 T_G = 250.0 <= 250.0
2 39 20 T_G = 250.0 <= 250.0
6 39 20 T_G = 250.0 <= 250.0
2 40 20 T_G = 250.0 <= 250.0
6 40 20 T_G = 250.0 <= 250.0
2 41 20 T_G = 250.0 <= 250.0
6 41 20 T_G = 250.0 <= 250.0
2 42 20 T_G = 250.0 <= 250.0
6 42 20 T_G = 250.0 <= 250.0

ERROR check_data_30.f:299
Unphysical field variables detected on one or more processes.

I then try a simple case that does not have chemical reaction and just heats the particle inside the spouted bed. This error appeared again.

I supposed that T_G is the temperature of gas and is lower than 250K but I do not understand why since the inlet temperature is 300 centigrade. Can anyone tell me what I was wrong? I really appreciate your help!

spouted_bed_pseudo_2d_with_chemistry.zip (8.0 KB)

1 Like
#2

Although you have an STL file, the computational domain is truncated in the x-direction to obtain a thin, quasi-2d geometry. You need to define Left (x=xmin) and right (x=xmax) regions and apply a adiabatic NSW BC to them.

2 Likes
#3

Thank you for your reply. The problem is solved.

But it seems that the particles are not heated by the high temperature inlet gas. The temperature range of the color bar of the particle is always from 0 to 1 and the color of the particle never change. Is there any way to set the range of the bar or is generated automatically? But at least I think the color of the particle should change since it is heated. Could you tell me where I was wrong? Thank you!

#4

My guess is the color bar shows the cell field, not point field (is the color bar titled “EP_G”, i.e. the void fraction)? If so, please expend the “Color Bar” setting and make sure the Field is set to “points”. Then expend the “Points” settings, set the variable to “Temperature”, click the color map, then “autoscale”, and “apply”. You may also want to hide the cell data by clicking on the icon located to the left of “Cells/Nodes”

1 Like
#5

Hello, I also have this problem, Could you tell me the reason and how to solve this problem. Thank you.

#6

Thank you so much!! The problem is solved. I did not click the ‘autoscale’ before.

#7

You can refer to Jeff’s reply. My two problem are solved based on it.

#8

Hi Jeff, can I ask you one more question? It seems that the chemical reaction fail to react in my case because HgO, HgS and HgCl2 are supposed to decompose with the increase of temperature. But the results shows that their mass fraction did not change during 30 second. I am confusing since the case can run successfully and the temperature of the particle is indeed increasing with time.

Could you give me a clue about this problem? Thank you in advance!

#9

I am referring to the zip file you attached earlier in the post thread. Please double check the reaction rates. The exponential basically returns zero due to the large negative term. The user coefficients c(1) to c(4) are not defined, which sets what we call an UNDEFINED value to them. UNDEFINED is actually a very large number (9.87654321E31) that is meant to easily catch an undefined variable. This would typically cause the simulation to crash, but since you are basically multiplying by zero (the exponential term), the reaction rates is zero. You need to set values for c(1) to c(4) and review the exponential terms so you get decent reaction rates.

#10

Hi Jeff, I modified the reaction rate but this time the simulation cannot converge and it shows that ‘Negative gas density detected’. Do you know what is wrong this time? I attached the modified usr_rates_des.f and .mfix file for your reference. Thank you!
2d_spouted_be_baseline_test3_heating.mfx
(33.2 KB) usr_rates_des.f (3.0 KB)