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-   -   coldEngineFoam (OpenFoam 2.1.x), constant Temperature during adiabatic compression (http://www.cfd-online.com/Forums/openfoam-verification-validation/113512-coldenginefoam-openfoam-2-1-x-constant-temperature-during-adiabatic-compression.html)

novakm February 20, 2013 21:43

coldEngineFoam (OpenFoam 2.1.x), constant Temperature during adiabatic compression
 
Dear Foamers.

In past two weeks I have been tempting to proove that coldEngineFoam satisfies the basic conservation laws (mass, I law of TD., ...).
Unpleasant surprise appeared in a simple adiabatic case, compression of perfect gas (air) in simple cylindre by moving of the ground ( ~ piston).
The pressure in the adiabatic process has to follow the adiabat, given by eq. pV^{kappa} = konst, where kappa = 1.4 for air (sorry for boring you with basics). However, the pressure obtained by OpenFoam does not fit even remotely the correct adiabat. Moreover, during adiabatic compression and expansion, the computed temperature remains constant.:confused:

Could you, dear Foamers, be so polite and tell me, where I made a mistake or what stands behinds the constant temperature?

Yours sincerely

Martin


The case
coldEngineFoam_adiabaticCompression.tar.gz (6.7 MB)
https://mega.co.nz/#!OABUmSyY!JAjUGi...xXhQ3Pqtv9N3tI

In order to reproduce run the Allrun.sh


For time saving purposes type in the constant/polymesh/blockMeshDict.m4

define(NPS, 50) //how many cells in the square section
define(NPD, 50) //how many cells from square section to perimeter
define(NPY, 20) // how many cells from top to bottom

to

define(NPS, 20) //how many cells in the square section
define(NPD, 20) //how many cells from square section to perimeter
define(NPY, 10) // how many cells from top to bottom
or etc.

mturcios777 February 25, 2013 13:25

Hi Martin,

I was away for the weekend and didn't see your post until today. I saw that there was a bug report and fix for some issues with coldEngineFoam; did updating to these fix your problem?


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