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-   -   Check for property conservation in a closed domain (https://www.cfd-online.com/Forums/fluent/86581-check-property-conservation-closed-domain.html)

 Yr0gErG March 27, 2011 06:44

Check for property conservation in a closed domain

How would you ensure property conservation in a closed domain?
For example if the entire domain is closed and only heat energy is coming in, is it safe to assume that properties like mass flow rate are always conserved?

 momech March 27, 2011 08:47

hi.
if you work on 2D case,just enough to creat an arbitrary line in the domain so you can check the mass flow rate through it. (it should be almost zero[flow circulation!]){also it's better to use some lines at different positions}
And in 3D case creat planes...
good luck.

 Yr0gErG March 27, 2011 14:04

mins is a 3D case... is the default interior good enough?

 Yr0gErG March 28, 2011 00:52

Hi, I tried the above mentioned suggestion, created two arbitrary planes within my domain and check for mass flow rate conservation. Is that correct? after about 200 iterations though, the mass flow rate started to oscillate quite largely. any advice?

 momech March 28, 2011 01:54

Hi,as I mentioned before,it should come nearly zero{total mass flow rate through each plane}
you can:
alter your Turb. method, do further iterations to achieve the more accurate convergence,check the grid quality and....

 Yr0gErG March 28, 2011 04:52

ok i am using the incompressible ideal gas density for air and the RNG k-e turbulence model. the residuals and mass flow rate no longer oscillate. however, the mass flow rate is very slowly increasing with more iterations.

 Yr0gErG March 28, 2011 05:15

Grid Check

Domain Extents:
x-coordinate: min (m) = -5.000000e-01, max (m) = 5.000000e-01
y-coordinate: min (m) = -5.000000e-01, max (m) = 5.000000e-01
z-coordinate: min (m) = -5.000000e-01, max (m) = 5.000000e-01
Volume statistics:
minimum volume (m3): 1.250000e-04
maximum volume (m3): 1.250000e-04
total volume (m3): 1.000000e+00
Face area statistics:
minimum face area (m2): 2.500000e-03
maximum face area (m2): 2.500000e-03
Checking number of nodes per cell.
Checking number of faces per cell.
Checking number of cells per face.
Checking face cells.
Checking bridge faces.
Checking right-handed cells.
Checking face handedness.
Checking face node order.
Checking element type consistency.
Checking boundary types:
Checking face pairs.
Checking periodic boundaries.
Checking node count.
Checking nosolve cell count.
Checking nosolve face count.
Checking face children.
Checking cell children.
Checking storage.
Done.

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