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arunss May 18, 2010 07:28

Fatal Bound Error
 
I am trying to do heat transfer analysis so i have introduced negative heat flux on the surface from 1000 to 100000 but when i give greater than -110000 heat flux value it converged but while writing the output it shows error as below

Locale : WALL
Variable : Density

Writing crash recovery file

ERROR #001100279 has occurred in subroutine ErrAction.
Message:
Stopped in routine ENFORCE_BOUNDS

An error has occurred in cfx5solve:

The ANSYS CFX solver exited with return code 1. No results file
has been created.

End of solution stage.

ghorrocks May 18, 2010 07:51

Looks like an error where the bounds of density were exceeded and it probably ended up with either a huge or negative density. Are you sure the simulation converged?

lffabiani May 18, 2010 10:14

arunss,

Try checking the variable range information (on the OUT file), especifically the density part. It sounds like the density is way off the scale, and it generates this error.

arunss May 18, 2010 12:38

Quote:

Originally Posted by lffabiani (Post 259303)
arunss,

Try checking the variable range information (on the OUT file), especifically the density part. It sounds like the density is way off the scale, and it generates this error.


I tried with variable range information while stating the density value is 3.9 at the point where it converged the value is 4.3 there is no much change in the density. i tried by doing backup for every 25 iteration but it save till 100 iteration at 125 iteration it shows the same error(actually it converged at 230 iteration)

lffabiani May 18, 2010 12:54

arunss,

On "expert parameters", "I/O Control", enable the "monitor ranges" option (set it to "t" as in TRUE)

Check the iteration where the solver gives the error, and check the "Variable Range Information" table that will be available on your OUT file

What's the min and max value of density?

arunss May 18, 2010 13:05

Quote:

Originally Posted by lffabiani (Post 259343)
arunss,

On "expert parameters", "I/O Control", enable the "monitor ranges" option (set it to "t" as in TRUE)

Check the iteration where the solver gives the error, and check the "Variable Range Information" table that will be available on your OUT file

What's the min and max value of density?

For 100 iteration it save the output as backup
+--------------------------------------------------------------------+
| Writing backup file 100_full.bak |
| Name : Backup Results 1 |
| Type : Standard |
| Option : Iteration Interval |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| Average Scale Information |
+--------------------------------------------------------------------+

Domain Name : Domain 1
Global Length = 1.2495E-01
Minimum Extent = 1.1299E-01
Maximum Extent = 1.0000E+00
Density = 4.2201E+00
Dynamic Viscosity = 1.0000E-05
Velocity = 2.3687E+01
Advection Time = 5.2749E-03
Reynolds Number = 1.2490E+06
Speed of Sound = 8.5287E+02
Mach Number = 2.7774E-02
Thermal Conductivity = 1.0000E-02
Specific Heat Capacity at Constant Pressure = 1.2091E+03
Specific Heat Capacity at Constant Volume = 9.0904E+02
Specific Heat Ratio = 1.3301E+00
Prandtl Number = 1.2091E+00
Temperature Range = 4.5251E+02


+--------------------------------------------------------------------+
| Average Scale Information |
+--------------------------------------------------------------------+


For 125 iteration
Domain Name : Domain 1
Global Length = 1.2495E-01
Minimum Extent = 1.1299E-01
Maximum Extent = 1.0000E+00
Density = 4.2127E+00
Dynamic Viscosity = 1.0000E-05
Velocity = 2.3960E+01
Advection Time = 5.2149E-03
Reynolds Number = 1.2612E+06
Speed of Sound = 8.5365E+02
Mach Number = 2.8068E-02
Thermal Conductivity = 1.0000E-02
Specific Heat Capacity at Constant Pressure = 1.2091E+03
Specific Heat Capacity at Constant Volume = 9.0904E+02
Specific Heat Ratio = 1.3301E+00
Prandtl Number = 1.2091E+00
Temperature Range = 4.4423E+02

Locale : WALL

it shows error

lffabiani May 18, 2010 13:11

Check for something like:

+--------------------------------------------------------------------+
| Variable Range Information |
+--------------------------------------------------------------------+

Domain Name : Domain 1
+--------------------------------------------------------------------+
| Variable Name | min | max |
+--------------------------------------------------------------------+
| Density | 1.88E-01 | 8.00E-01 |
| Specific Heat Capacity at Constant Pressure| 1.27E+03 | 2.21E+03 |
| Dynamic Viscosity | 1.11E-05 | 1.68E-05 |
| Thermal Conductivity | 2.12E-02 | 3.43E-02 |
| Isothermal Compressibility | 9.84E-06 | 9.91E-06 |
| Static Entropy | 8.03E+03 | 1.16E+04 |
| N2.Density | 1.66E-01 | 1.13E+00 |
| N2.Specific Heat Capacity at Constant Press| 1.04E+03 | 1.29E+03 |
| N2.Dynamic Viscosity | 1.77E-05 | 1.77E-05 |
+---------------------------------------------------------------------

arunss May 19, 2010 06:16

Quote:

Originally Posted by lffabiani (Post 259348)
Check for something like:

+--------------------------------------------------------------------+
| Variable Range Information |
+--------------------------------------------------------------------+

Domain Name : Domain 1
+--------------------------------------------------------------------+
| Variable Name | min | max |
+--------------------------------------------------------------------+
| Density | 1.88E-01 | 8.00E-01 |
| Specific Heat Capacity at Constant Pressure| 1.27E+03 | 2.21E+03 |
| Dynamic Viscosity | 1.11E-05 | 1.68E-05 |
| Thermal Conductivity | 2.12E-02 | 3.43E-02 |
| Isothermal Compressibility | 9.84E-06 | 9.91E-06 |
| Static Entropy | 8.03E+03 | 1.16E+04 |
| N2.Density | 1.66E-01 | 1.13E+00 |
| N2.Specific Heat Capacity at Constant Press| 1.04E+03 | 1.29E+03 |
| N2.Dynamic Viscosity | 1.77E-05 | 1.77E-05 |
+---------------------------------------------------------------------





For iteration 1

+--------------------------------------------------------------------+
| Variable Range Information |
+--------------------------------------------------------------------+

Domain Name : Domain 1
+--------------------------------------------------------------------+
| Variable Name | min | max |
+--------------------------------------------------------------------+
| Density | 3.83E+00 | 3.96E+00 |
| Specific Heat Capacity at Constant Pressure| 1.21E+03 | 1.21E+03 |
| Dynamic Viscosity | 1.00E-05 | 1.00E-05 |
| Thermal Conductivity | 1.00E-02 | 1.00E-02 |
| Isothermal Compressibility | 4.34E-07 | 4.35E-07 |
| Static Entropy | 1.32E+03 | 1.36E+03 |
| Velocity u | 2.67E-01 | 7.44E+00 |
| Velocity v | -1.49E+00 | 1.44E+00 |
| Velocity w | -1.56E+00 | 1.59E+00 |
| Pressure | 2.20E+06 | 2.20E+06 |
| Turbulence Kinetic Energy | 1.01E-03 | 2.51E-02 |
| Turbulence Eddy Dissipation | 3.55E-03 | 3.75E-01 |
| Eddy Viscosity | 4.55E-05 | 1.61E-03 |
| Temperature | 1.94E+03 | 2.00E+03 |
| Static Enthalpy | 1.98E+06 | 2.06E+06 |
+--------------------------------------------------------------------+


For 100th iteration

+--------------------------------------------------------------------+
| Variable Range Information |
+--------------------------------------------------------------------+

Domain Name : Domain 1
+--------------------------------------------------------------------+
| Variable Name | min | max |
+--------------------------------------------------------------------+
| Density | 3.57E+00 | 4.96E+00 |
| Specific Heat Capacity at Constant Pressure| 1.21E+03 | 1.21E+03 |
| Dynamic Viscosity | 1.00E-05 | 1.00E-05 |
| Thermal Conductivity | 1.00E-02 | 1.00E-02 |
| Isothermal Compressibility | 4.24E-07 | 4.67E-07 |
| Static Entropy | 1.05E+03 | 1.39E+03 |
| Velocity u | -2.29E+01 | 2.97E+02 |
| Velocity v | -6.55E+01 | 5.79E+01 |
| Velocity w | -7.61E+01 | 7.43E+01 |
| Pressure | 2.04E+06 | 2.26E+06 |
| Turbulence Kinetic Energy | 8.92E-04 | 2.76E+02 |
| Turbulence Eddy Dissipation | 2.75E-03 | 2.05E+07 |
| Eddy Viscosity | 1.68E-05 | 8.90E-03 |
| Temperature | 1.55E+03 | 2.00E+03 |
| Static Enthalpy | 1.51E+06 | 2.06E+06 |
+--------------------------------------------------------------------+

After converged at 220 iteration
+--------------------------------------------------------------------+
| Variable Name | min | max |
+--------------------------------------------------------------------+
| Density | 3.55E+00 | 4.95E+00 |
| Specific Heat Capacity at Constant Pressure| 1.21E+03 | 1.21E+03 |
| Dynamic Viscosity | 1.00E-05 | 1.00E-05 |
| Thermal Conductivity | 1.00E-02 | 1.00E-02 |
| Isothermal Compressibility | 4.24E-07 | 4.69E-07 |
| Static Entropy | 1.06E+03 | 1.39E+03 |
| Velocity u | -2.38E+01 | 3.04E+02 |
| Velocity v | -6.68E+01 | 5.91E+01 |
| Velocity w | -7.76E+01 | 7.86E+01 |
| Pressure | 2.03E+06 | 2.26E+06 |
| Turbulence Kinetic Energy | 7.95E-04 | 2.87E+02 |
| Turbulence Eddy Dissipation | 2.31E-03 | 2.18E+07 |
| Eddy Viscosity | 1.22E-05 | 4.68E-03 |
| Temperature | 1.55E+03 | 2.00E+03 |
| Static Enthalpy | 1.51E+06 | 2.06E+06 |
+--------------------------------------------------------------------+

Fatal bounds error detected
---------------------------
Variable: Density
Locale : WALL

+--------------------------------------------------------------------+
| Writing crash recovery file |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| ERROR #001100279 has occurred in subroutine ErrAction. |
| Message: |
| Stopped in routine ENFORCE_BOUNDS |
| |
| |
| |
| |
| |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| An error has occurred in cfx5solve: |
| |
| The ANSYS CFX solver exited with return code 1. No results file |
| has been created. |
+--------------------------------------------------------------------+

End of solution stage.

+--------------------------------------------------------------------+
| Warning! |
| |
| The ANSYS CFX Solver has written a crash recovery file. This file |
| has been saved as C:\Documents and Settings\Arun Kumar\Desktop\27 |
| April Home\GG_012.res.err and may be an aid to diagnosing the |
| problem or restarting the run. More details should be available |
| in the solver output section of the output file. |
+--------------------------------------------------------------------+

lffabiani May 20, 2010 11:59

Aruns,

The only strange thing is the pressure: 2.26E+06 Pa is 22 bar... does this correspond to what you are trying to simulate?

Can you give a brief description of the problem?

Best regards

arunss May 21, 2010 11:51

Quote:

Originally Posted by lffabiani (Post 259568)
Aruns,

The only strange thing is the pressure: 2.26E+06 Pa is 22 bar... does this correspond to what you are trying to simulate?

Can you give a brief description of the problem?

Best regards

Thanks Iffabiani
I try to simulate gas generator system, which meas it store the gas with high temperature about 2000K and pressure about 23 bar in the chamber and it passes through converged diverged nozzle and exit via two pipes. the exit condition is pressure 22 bar, mass flow rate 6.5 gms/ sec and temperature 1273K, To reduce the temperature of the gas i introduced heat flux on wall (without heat flux the temperature is 2000K), i uploaded the geometry of the model the link has been given below

http://www.loadmypicture.com/getimag...2344397362.jpg

Total Size is about 0.5m length

Chamber dia -115mm and length is 150mm and it converged to dia 5 mm
and length of converged section is 75mm and diverged section end diameter is 12.7mm and length 75 mm and two pipes are connected

lffabiani May 21, 2010 12:51

Arun,

In which walls are you trying to set the heat flux? If this wall is too small, there will be a lot of heat exchange going on a very small area, and this could cause numerical errors.

arunss May 22, 2010 03:27

Quote:

Originally Posted by lffabiani (Post 259766)
Arun,

In which walls are you trying to set the heat flux? If this wall is too small, there will be a lot of heat exchange going on a very small area, and this could cause numerical errors.

I am trying to set heat flux in two pipes which has 12.5mm diameter and 300mm length, i started with negative heat flux from 1000 to 110000 i didn't get any error. if i give more than 110000 it converged but shows the error while writing the file.
So i increase the pipe length from 300mm to 700mm still i am getting the same error


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