Getting the quantities of the species as a field for further post processing

TL- · October 6, 2021, 13:19

Hey all,

I am simulating a chemical reaction with rhoReactingFoam and I want to calculate my rate of conversion. To be able to do so I need a new field with the molar quantities of my species. So far I've only found a way to display the molar fractions.

Is there a way to create a new output with the moles of my species?

Thanks in advance

dlahaye · October 6, 2021, 13:36

Reaction rates can be obtained in post-processing.

I posted a list of quantities that can be obtained in post-processing in What is Object Registry in OpenFOAM? Item #9

Good luck, D.

TL- · October 7, 2021, 02:20

Thanks for your reply. Unfortunately I'm not looking for a way to get the reaction rates but the conversion of my reaction system. Do you know a way to do that in OpenFOAM or paraview?

dlahaye · October 8, 2021, 06:56

How is this conversion defined?

TL- · December 20, 2021, 12:04

Rate of conversion ist defined as $X = \frac{n_{A,0} - n_A}{n_{A,0}}$

If someone stumbles upon this post in search for an answer:
I rewrote the rate of conversion to the following form:
$X_{i} = \frac{\dot n_{i,in} - \dot n_{i,out}}{\dot n_{i,in}} = \frac{\frac{\dot m_{i,in}}{M_{i}} - \frac{\dot m_{i,out}}{M_{i}}}{\frac{\dot m_{i,in}}{M_{i}}} = \frac{\dot m_{i,in} - \dot m_{i,out}}{\dot m_{i,in}} = \frac{\dot m_{in} \cdot w_{i,in} - \dot m_{out} \cdot w_{i,out}}{\dot m_{in} \cdot w_{i,in}}$

To get the massflow of each species I needed to do some post processing (which can be directly added to the controlDict for further cases). To get the overall mass flow I used the post processing functions:

postProcess -func "flowRatePatch(name=inlet)
postProcess -func "flowRatePatch(name=outlet)

This provides me with an overview of my inlet and outlet massflow.

To optain the mass fractions of each species I used paraView. As the desired mesh region I checked inlet or outlet respectively and used the integrateVariables filter. There I checked "Divide Cell Data by Volume" property. This outputs the mass fraction of each species in the inlet/ outlet stream.

I used the makro feature of paraView to implement all of this in python code, which saves the values over time inside a .csv file for further use.

October 6, 2021, 13:19	Getting the quantities of the species as a field for further post processing	#1
TL- New Member Join Date: Apr 2021 Posts: 4 Rep Power: 5	Hey all, I am simulating a chemical reaction with rhoReactingFoam and I want to calculate my rate of conversion. To be able to do so I need a new field with the molar quantities of my species. So far I've only found a way to display the molar fractions. Is there a way to create a new output with the moles of my species? Thanks in advance

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October 6, 2021, 13:36		#2
dlahaye Senior Member Domenico Lahaye Join Date: Dec 2013 Posts: 730 Blog Entries: 1 Rep Power: 17	Reaction rates can be obtained in post-processing. I posted a list of quantities that can be obtained in post-processing in What is Object Registry in OpenFOAM? Item #9 Good luck, D.

October 7, 2021, 02:20		#3
TL- New Member Join Date: Apr 2021 Posts: 4 Rep Power: 5	Thanks for your reply. Unfortunately I'm not looking for a way to get the reaction rates but the conversion of my reaction system. Do you know a way to do that in OpenFOAM or paraview?

October 8, 2021, 06:56		#4
dlahaye Senior Member Domenico Lahaye Join Date: Dec 2013 Posts: 730 Blog Entries: 1 Rep Power: 17	How is this conversion defined?

December 20, 2021, 12:04		#5
TL- New Member Join Date: Apr 2021 Posts: 4 Rep Power: 5	Rate of conversion ist defined as $X = \frac{n_{A,0} - n_A}{n_{A,0}}$ If someone stumbles upon this post in search for an answer: I rewrote the rate of conversion to the following form: $X_{i} = \frac{\dot n_{i,in} - \dot n_{i,out}}{\dot n_{i,in}} = \frac{\frac{\dot m_{i,in}}{M_{i}} - \frac{\dot m_{i,out}}{M_{i}}}{\frac{\dot m_{i,in}}{M_{i}}} = \frac{\dot m_{i,in} - \dot m_{i,out}}{\dot m_{i,in}} = \frac{\dot m_{in} \cdot w_{i,in} - \dot m_{out} \cdot w_{i,out}}{\dot m_{in} \cdot w_{i,in}}$ To get the massflow of each species I needed to do some post processing (which can be directly added to the controlDict for further cases). To get the overall mass flow I used the post processing functions: postProcess -func "flowRatePatch(name=inlet) postProcess -func "flowRatePatch(name=outlet) This provides me with an overview of my inlet and outlet massflow. To optain the mass fractions of each species I used paraView. As the desired mesh region I checked inlet or outlet respectively and used the integrateVariables filter. There I checked "Divide Cell Data by Volume" property. This outputs the mass fraction of each species in the inlet/ outlet stream. I used the makro feature of paraView to implement all of this in python code, which saves the values over time inside a .csv file for further use.