CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Post-Processing

[PostProcess] Qdot - related to Arrhenius-kinetics?

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   April 17, 2021, 14:35
Post [PostProcess] Qdot - related to Arrhenius-kinetics?
  #1
Senior Member
 
alainislas's Avatar
 
Alain Islas
Join Date: Nov 2019
Location: Mexico
Posts: 142
Rep Power: 6
alainislas is on a distinguished road
Hello everyone

I am working my case with coalChemistryFoam, solving for some gas and particle reactions. I am interested in knowing what is the total heat release of my reactions (in Joules). OpenFOAM exports Qdot in units [J / (m^3 s)]. Hence, I assume I can simply perform:

\text{Total Heat Release} = \sum_{j=1} \left[\sum_{i=1} \text{Q}_\text{dot} dV_{i} \right] dt_{j}

For the volume integral, I am using a volIntegrate operation in my controlDict.

Code:
functions
{

	volFieldValue1
	{
	    type            volFieldValue;
	    libs            ("libfieldFunctionObjects.so");

	    log             yes;
	    writeControl    timeStep;
	    writeInterval	1;
	    writeFields     true;

	    regionType      cellZone;
	    name            FLUID_SPHERE; //<-- This is my whole domain
	    operation       volIntegrate;

	    fields
	    (
		Qdot
	    );
}
Then I can simply integrate over time. However, I am testing various Pre-exponential factors and Activation Temperatures, and Im getting different values for the Heat Release. I don't see the dependency of the Heat Release with Arrhenius-kinetics.

Does anyone know if Im treating Qdot correctly?
Attached Images
File Type: jpg 1.jpg (64.3 KB, 44 views)
alainislas is offline   Reply With Quote

Old   November 22, 2021, 10:32
Red face dear alainislas
  #2
New Member
 
wangh
Join Date: Jul 2020
Posts: 10
Rep Power: 5
heheda is on a distinguished road
Can you please tell me what the full command for Qdot is? I use "postProcess -func Qdot" but it gives me an error. Thank you very much!
heheda is offline   Reply With Quote

Old   December 2, 2021, 00:24
Default
  #3
Senior Member
 
Charles
Join Date: Aug 2016
Location: Vancouver, Canada
Posts: 148
Rep Power: 9
Marpole is on a distinguished road
You can do it with a post-processing command below. But it doesn't work properly. The results are all zero. I guess its a bug.
Code:
reactingFoam -postProcess -func Qdot
You can also do it in run-time by putting the following at the end of file controlDict. It works fine. The unit is J/m^3-s. So the number is very large and varies a lot cell by cell. The flame contour plot is not very smooth.
Code:
functions
{
    #includeFunc Qdot
}
__________________
Charles L.
Marpole is offline   Reply With Quote

Old   December 2, 2021, 00:46
Default
  #4
Senior Member
 
Charles
Join Date: Aug 2016
Location: Vancouver, Canada
Posts: 148
Rep Power: 9
Marpole is on a distinguished road
If you want to get the total heat release rate, one way to obtain it without programming is to use integrateVariables and plotDataOverTime features of paraFoam or paraview. When you do integrate, don't turn on "Divide Cell Data by Volume". And you do plotDataOverTime, select "Cells" in Field Association. After you plot it out, you can "save data" to get the trace.
__________________
Charles L.
Marpole is offline   Reply With Quote

Reply

Tags
coalchemistryfoam, qdot, reacting

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On



All times are GMT -4. The time now is 00:28.