[N. A.]

Hello All,

I am trying to calculate the average mass flow rate of a particular species passing through a plane in the geometry, such as mass flow rate of CO2 passing through a plane.

Can you please let me know if know how we can extract this information in paraview.

Is there a way to calcualte this value directly in OpenFOAM

Thanks,
Nir

[Tobi]

Hi,

your post is old and you just made four posts so I think none will answer me.

Do you find out how that works?

If someone can explain it, it would be very good for me and all the others


Tobi

[tomf]

Hello Tobi,

How are you?

I think I may be able to help you on this one. The most easy way to do this with paraView would be to calculate the total mass flow through a plane using Y_CO2*rho*U_n where U_n is the velocity component normal to the plane of interest and Y_CO2 is the mass fraction of CO2. If you have a plane not aligned with x, y or z, you can use the calculator filter or the surface flow filter to get the velocity components perpendicular to that plane. Make sure the calculator for rho*U_n works on the cell data. Than go to filters>integrate Variables and you will get a table with the integral Y_CO2*rho*U*dA over Area A. This is the mass of CO2 passing through the area.

I do not have an example for doing this during the calculation, but I think something can be done with swak4Foam.

Regards,
Tom

[Tobi]

Originally Posted by tomf

Hello Tobi,

How are you?

I think I may be able to help you on this one. The most easy way to do this with paraView would be to calculate the total mass flow through a plane using Y_CO2*rho*U_n where U_n is the velocity component normal to the plane of interest and Y_CO2 is the mass fraction of CO2. If you have a plane not aligned with x, y or z, you can use the calculator filter or the surface flow filter to get the velocity components perpendicular to that plane. Make sure the calculator for rho*U_n works on the cell data. Than go to filters>integrate Variables and you will get a table with the integral Y_CO2*rho*U*dA over Area A. This is the mass of CO2 passing through the area.

I do not have an example for doing this during the calculation, but I think something can be done with swak4Foam.

Regards,
Tom

Hi Tom,

I am fine. I have two weeks left to finish my masterthesis. Did you follow the libOpenSmoke thread? I find some fatal bugs in the tool and will bring out my updated model after I finished my thesis. So I think in 4 Weeks everything is avaiable (maybe + validation and description). To tool is very nice but there are some problems with the enthalpie. But I solved it


Thanks for your replay. I am too stupid
But I test it in the thermolibrary. therefor I ll create a new scalarField and will calculate the CO-emission in PPM directly. I think it should be possible and then I can compare it.

Tobi

[tomf]

Hi Tobi,

Yes I did follow the libOpenSmoke thread, looks like you have some interesting results!

But I test it in the thermolibrary. therefor I ll create a new scalarField and will calculate the CO-emission in PPM directly. I think it should be possible and then I can compare it.

Sounds like a plan,

good luck
Tom

[Tobi]

Hi Tom,

one question to you.

If I want the massweighted species in the whole fluid domain, is it possible to do like you said with mag(U) then?

[Tobi]

Hi Tom,

just one question, if I make everything correct.


I wanna calculate CO in ppm on a patch.

Therefor I calculate the Mean molmass with:


M_aver = sum(Y_i / M_i) of CO, O2, H2O, N2, CO2, H2, OH

After that I calculate CO in ppm like:


COppm = M_aver/M_CO * Y_CO * 1.000.000

Well the temperature profil looks better with OpenFOAM compared with ansys but if I look to the CO emissions there is so a huge difference:


Measurement 80 ppm
Ansys 60 ppm
OF 0.0013 ppm


I am not sure if I make everything correct!

[tomf]

Originally Posted by Tobi

Hi Tom,

just one question, if I make everything correct.


I wanna calculate CO in ppm on a patch.

Therefor I calculate the Mean molmass with:


M_aver = sum(Y_i / M_i) of CO, O2, H2O, N2, CO2, H2, OH

After that I calculate CO in ppm like:


COppm = M_aver/M_CO * Y_CO * 1.000.000

Well the temperature profil looks better with OpenFOAM compared with ansys but if I look to the CO emissions there is so a huge difference:


Measurement 80 ppm
Ansys 60 ppm
OF 0.0013 ppm


I am not sure if I make everything correct!

Hi Tobi,

I would think you have:

M_aver = sum(Y_i * M_i)/sum (Y_i) = sum(Y_i * M_i)

and I agree with your calculation of COppm.
Regards,
Tom

[Tobi]

Originally Posted by tomf

Hi Tobi,

I would think you have:

M_aver = sum(Y_i * M_i)/sum (Y_i) = sum(Y_i * M_i)

and I agree with your calculation of COppm.
Regards,
Tom

Hi Tom,

thanks for your replay.
I made a validation of my COppm calculation like I mentioned in the last post and its correct, like you told me

In that case I realized a other bug in the thermodynamics
but in my thesis there is no time for it. Maybe its a problem with the flameletgeneration.

Tobi

[wouter]

Hello,

Maybe a stupid thing to ask someone that is working on a thesis, but is ppm for gasses not volume based instead of mass based?

best regards
Wouter

[Tobi]

Originally Posted by wouter

Hello,

Maybe a stupid thing to ask someone that is working on a thesis, but is ppm for gasses not volume based instead of mass based?

best regards
Wouter

Hi,

ppm on (maybe) the species CO is based on the mol fraction [X_CO] * 1.000.000 = CO_ppm.

If you wanna get an information on a slice its better to make a mass weighted calculation to get the better result.

If you wanna get an information on a specified volume you should do a volume weighted calculation.

If I am wrong please correct me.

Greetings Tobi

[t.oliveira]

Originally Posted by N. A.

calculate the average mass flow rate of a particular species passing through a plane in the geometry [...] Is there a way to calculate this value directly in OpenFOAM

I had a similar problem (integrate a variable over an internal plane) and managed to do so. Please refer to http://www.cfd-online.com/Forums/ope...tml#post581774 . You may have to use areaNormalAverage instead of areaNormalIntegrate.

Best wishes,

Thomas