[OpenFOAM] How to save area-weighted OR mass-weighted Parameters from paraview

vineet_bhola · November 19, 2015, 09:12

Hi Guys,
I want to find out average values of Temperature, velocity etc of fluid crossing through inlet/outlet patches (or even any patch for that matter). But as I have used addLayers through Snappyhexmesh, I cannot directly take the mean value of these Parameters after "save data" command because different cells have different areas and thus different weightage.
Is there any option to choose individual face areas alongwith the traditional Parameters like T,P,U,k etc. while saving data from paraview.
OR if there is any preexisting filters for that?

Thanks
Vineet

tomf · November 20, 2015, 04:16

Hi Vineet,

If you look to "cell data" in spreadsheet view there should also be an area for a slice or a patch. This is the area for each face of your patch. When I want an average I usualy use the integrate variables filter and than a calculator filter. The integrated area of the patch is than a variable for the calculator, so you have:

$\overline{\phi} = \frac{\int \phi dA}{\int dA}$

Regards,
Tom

vineet_bhola · November 20, 2015, 05:16

Thanks a lot Tom,
It works as I wanted for area-weighted average. Although I don't see 'Area' field before integration in Spreadsheet view, I can see it only after I integrate the variables.
I still have some Problem with mass-weighted average. So in case I have varying densities across different faces of the patch, I also need to incorporate density into Integration. But integrate variable filter doesn't give this Option of taking two variables at a time.
For example for mass-weighted average I would rather need the formula to be :

Code:

Mass-weighted average = Integration (variable*density*dA) / Integration (density*dA)

PHP Code:


			
 \overline{\phi m}=\frac{\int \phi \rho dA}{\int \rho dA}

where \rho is density.
P.S. I don't know how to add Special characters as a formula

Is that possible with filters?

Thanks,
Vineet

tomf · November 20, 2015, 05:27

Hi Vineet,

The formula can be created using [math ] [\ math] blocks instead of the PHP that you used. The integrate variable filter integrates all the variables that are present. So if you need the mass average you would first need a calculator rho*phi and than do the integration. After that you can do another calculator filter just dividing by the integrated rho this time.

Regards,
Tom

vineet_bhola · November 20, 2015, 05:31

awesome...that sounds perfect...thanks once again.

November 19, 2015, 09:12	How to save area-weighted OR mass-weighted Parameters from paraview	#1
vineet_bhola Member Vineet Bhola Join Date: Jun 2015 Location: Chemnitz, Germany Posts: 49 Rep Power: 10	Hi Guys, I want to find out average values of Temperature, velocity etc of fluid crossing through inlet/outlet patches (or even any patch for that matter). But as I have used addLayers through Snappyhexmesh, I cannot directly take the mean value of these Parameters after "save data" command because different cells have different areas and thus different weightage. Is there any option to choose individual face areas alongwith the traditional Parameters like T,P,U,k etc. while saving data from paraview. OR if there is any preexisting filters for that? Thanks Vineet Luttappy likes this.

November 20, 2015, 05:16		#3
vineet_bhola Member Vineet Bhola Join Date: Jun 2015 Location: Chemnitz, Germany Posts: 49 Rep Power: 10	Thanks a lot Tom, It works as I wanted for area-weighted average. Although I don't see 'Area' field before integration in Spreadsheet view, I can see it only after I integrate the variables. I still have some Problem with mass-weighted average. So in case I have varying densities across different faces of the patch, I also need to incorporate density into Integration. But integrate variable filter doesn't give this Option of taking two variables at a time. For example for mass-weighted average I would rather need the formula to be : Code: Mass-weighted average = Integration (variabledensitydA) / Integration (density*dA) PHP Code: `\overline{\phi m}=\frac{\int \phi \rho dA}{\int \rho dA}` where \rho is density. P.S. I don't know how to add Special characters as a formula Is that possible with filters? Thanks, Vineet

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November 20, 2015, 04:16		#2
tomf Senior Member Tom Fahner Join Date: Mar 2009 Location: Breda, Netherlands Posts: 634 Rep Power: 32	Hi Vineet, If you look to "cell data" in spreadsheet view there should also be an area for a slice or a patch. This is the area for each face of your patch. When I want an average I usualy use the integrate variables filter and than a calculator filter. The integrated area of the patch is than a variable for the calculator, so you have: $\overline{\phi} = \frac{\int \phi dA}{\int dA}$ Regards, Tom

November 20, 2015, 05:27		#4
tomf Senior Member Tom Fahner Join Date: Mar 2009 Location: Breda, Netherlands Posts: 634 Rep Power: 32	Hi Vineet, The formula can be created using [math ] [\ math] blocks instead of the PHP that you used. The integrate variable filter integrates all the variables that are present. So if you need the mass average you would first need a calculator rho*phi and than do the integration. After that you can do another calculator filter just dividing by the integrated rho this time. Regards, Tom

November 20, 2015, 05:31		#5
vineet_bhola Member Vineet Bhola Join Date: Jun 2015 Location: Chemnitz, Germany Posts: 49 Rep Power: 10	awesome...that sounds perfect...thanks once again.