[torvic]

Hello

Hope you're doing fine.
I have a question about "fieldAverage"

I saw its use in the controlDict of oodles, but where can I find the code for the "fieldAverage" function. I checked out "sampling" directory but only found "probes".

I want to take the average of other quantities, say a chemical specie.

Does "fieldAverage" allow for this ?

thanks in advance

Best

V

[lakeat]

1. It's in src/postProcessing.
2. I think so.

[lakeat]

Well, I know where the problem is.
According to the numbering of cells, postChannel's channelIndexing.C should have a few modifications.

Best,
Daniel

[torvic]

Hi Daniel

sorry for the late reply.

you're right, fieldAverage it's already there. I will see how to add the chemical specie field

Thanks so much for your help !

best

V

[nishant_hull]

Hi foamers...

I can see that the postChannel utility is not working as the structure of new channelOodles solver has been changed. Now the R field is not being written.
however I want to compare the stress components across the channel and therefore i need the urms and vrms value of the the velocity. ( I took these urms and vrms terms from postchannel utility declaration). How can we obtain these stress values now?

I again have some doubt about the UPrime2Mean. is this UPrime2Mean is stress-components along xx, yy and zz?? If yes, then what about the stress component in XY direction? (which was termed as "uv" in postChannel utility)

your comments plase!

cheers!
Nishant

[lakeat]

1. Easy, just copy some lines from OF-1.4.1
2. Please read the ProgrammerGuide P-16, item "Symmetric rank 2".

Daniel

[nishant_hull]

Thanks Daniel

2) I understand that the 6 components will give me the all stresses and I can see those 6 stresses in the file UPrime2Mean. but How to extract/sample the individual component of the stress from the file UPrime2Mean? I tried sample utility but they do not sample UPrime2Mean field. Doing it in excel is another option but isn't there some available method?

1) Do you mean, I should copy those postchannel-utility files and recompile my openfoam solver? Could you please tell me which files you are referring to?

Thanks once again.
Nishant

[lakeat]

1) Compare version 1.4.1 and 1.5, note their differences, and you will find a file called calculateAverages.H, try to use it in OF-1.5, and recompile the channeloodles solver.

2) For me, I use postChannel Utility as a template. Note how the utility treat R field and get u'u', u'v', etc., you will know what I mean.

Regards, Daniel

[nishant_hull]

Thanks Daniel
Its been great help for me.
I have done some editing in postChannel utility and I have considered UPrime2Mean and R to be same symmmTensor and replaced R with UPrime2Mean and recompiled the utility. Is it a right thing to do?
see the readField.c and collapse.H file
readFields.H
collapse.H

[nishant_hull]

Another question is:
Is there any recent modification in channelIndex.C file? I can see that you suggested some modification in that file.
Actually, I am getting some ambiguous result when I compare the results for channel flow using postChannel utility (modified by me) and sample utility available with foam. See the attached picture.. the Umean's x-component is plotted where green line is plotted using postchannel utility and red line is plotted with sample utility.


My channelIndex.C file is as follows:
channelIndex.C

[lakeat]

Hi Nishant!

1) Compare version 1.4.1 and 1.5, note their differences, then you will see what R means
2) Don't use UPrime2Mean, but use R to get what you want.
3) Include "calculateAverages.H" from OF-1.4.1 so that you can get R field.

Cheers,
Daniel

[nishant_hull]

hi Daniel

There is definetely some problem here. because I have a openfoam-1.4.1 installed on other system and when I plot the Uf with R field then I found that the same difference in Umean's x-component and Uf (which is also umean's x -component defined in postChannel/collapse.H).
What could be the reason for this difference? Why there is different plot for same variable plot? I might be wrong somewhere in my assumption.

Can anybody explain?

Nishant

[lakeat]

Sorry for my last post, I examined the case and found (please correct me if I am wrong),

1st, Huh... Don't know how did you get that graph!

2nd, the following are their relationship.
1.4.1 - R field - uniform/nAveragingSteps.raw
1.5 - UPrime2Mean field - uniform/fieldAveragingProperties

R=UPrime2Mean
They are both running average. So you don't nned to copy line from 1.4.1.

Remember everytime you do the reaveraging, don't forget to delete uniform dir.

Daniel

[nishant_hull]

Hi Daniel,
Thnaks for reply. Could you please try to compare your Umean.component(0) profile and Uf profile obtained from postchannel utility?? As per the code, they should be the same.
In case you are busy, then could you please send the tar dir of the channel395 case which provides you good Uf profile?

If any one can please see the problem mention on this forum dated September 04, 2008 and give me some suggestion then it would be of great help.

Nishant

[nishant_hull]

I got the solution to my problem.
its here..
http://www.cfd-online.com/OpenFOAM_D...es/1/3532.html

[lakeat]

Great!

[mattijs]

Hi Nishant, Daniel.

I wrote a postChannel that works on any layered and/or decomposed mesh and is simpler to use. Could you test it and let me know if it is correct? The sample dictionary should be self explanatory.

postChannel.tgz

[lakeat]

Thank you, Mattijs, I will try. (I have just returned from my National Day Holiday).
Regards, Daniel

[lakeat]

Hi,

A nice day to you.

I am thinking how to plot a E(k)-k curve? Could anyone give me some hints?
Is E(k) the same as file "k" in each time directory? I found k value is very small.
And if k=2*pi*f/U, then how can I get f?

The following are k versus 2*Pi/mag(U). I guess it is sgs turbulent energy.


How did you guys do that? In matlab or what?

Thank you.

Ps, the new postChannel works well, thank you Mattijs.

Regards, Daniel

[zebu83]

Hello everybody!

I download the new postChannel directory and i modify the postChannelDict, but it doesn't work!

old postChannelDict:

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

Nx 40;
Ny (50);
Nz 30;

// ************************************************** *********************** //

new postChannelDict:

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

Nx 40;
Ny
(
25
25
);
Nz 30;

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

I have to modify anithing else?

thank you

MT