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units after multipl. with phi

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Old   September 26, 2012, 11:01
Default units after multipl. with phi
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Tobias Holzmann
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Hi all,

I have an equation like that:

Code:
div(phi, H) + Q
Solver that is used is rhoSimpleFoam - compressible. The unit of H is [J/kg]. Q has the unit [W/m].

I had a look at the phi file and the file has the unit [kg/s]. Also I had a look at the createCompressiblePhi.H file and there is phi defined as the mass flow.

So after div(phi, H) I should get the unit [J/s] = [W] ...
Or am I wrong?

If phi = rho then everything would be nice
I am a bit confused.

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Old   September 26, 2012, 13:07
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Meindert de Groot
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Could it be that you are missing the cell volume from the finite volume integration in your Q term?

phi = rho would still not solve your problem, because you're still missing [1/s] in that case.
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Old   September 26, 2012, 13:12
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Hi,

no its implemented in the flamelet tool from alberto.
He added an enthalpy defect like that:

Code:
div(phi, H)
- laplacian(turbulence->mut/sigmat, H) 
+ Qrad
where Qrad is calculated with

Code:
Qrad = 4 * sigma_B * (T_cell^4 - T_env^4) * as
Like here: http://www.sandia.gov/TNF/radiation.html

Qrad [W/m]
H [J/kg]

Well - but you `re right. There is still a s missing :/
I a m confused with taht code.
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Old   September 28, 2012, 05:52
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Hi Tobi,

Have a look at equation 2.29 in the Programmer's Guide.
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Old   September 30, 2012, 08:11
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Quote:
Originally Posted by meindert View Post
Hi Tobi,

Have a look at equation 2.29 in the Programmer's Guide.
Hi,
do you mean the libOpenSmoke Guide or what programmers guide do you mean?
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Old   October 1, 2012, 10:30
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Hi Tobias,
the folks at OpenCFD have discontinued Programmers Guide that is correct

but you can still find
http://openfoam-extend.git.sourcefor...de.pdf;hb=HEAD
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Old   October 1, 2012, 13:32
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HI,

thanks very much.
Thats that what I need integration over a volume V - now I know how that works.

Thought that the programmers-guide is only the doxygen-code
Nice to know.

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Old   October 3, 2012, 17:24
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Perhaps it's good to know that you can also find it in your $WM_PROJECT_DIR/doc/Guides-a4 directory.
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Old   October 4, 2012, 15:55
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Quote:
Originally Posted by meindert View Post
Perhaps it's good to know that you can also find it in your $WM_PROJECT_DIR/doc/Guides-a4 directory.

Nice to know.
Working with OF for 3 years now and be in that directory some times but never realized that

stupid!

but thanks!
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