Ending the calculation / Mass flow direction

[Axel Cablé]

i,
I have two questions.
 
Ending the calculation
 
 
I would like to properly stop a calculation that is currently running. I tried putting a "ficstp" file in the /tmp/.. directory containing:
 
"blank line"
NTMABS=1200
 
but it does not work, the calculation keeps running. Any suggestion?
 
Mass flow direction
 
 
My studied domain consists in a parallelepiped, with two inlets (INLET and INFILTRATION) on two opposites faces and one free outlet (on the same face as INLET).
 
INLET: V=2.77m/s ; Mass flow: A = 4.897E-3
kg/s
INFILTRATION: V=0.446m/s ; Mass flow: B = 3.679E-4 kg/s
 
Hence, I should get a total incoming mass flow of A + B, and an outgoing mass flow of -(A+B).
Instead, I get (A-B) for incoming mass flow and -(A-B) for outgoing mass flow:
 
Boundary type          Code    Nb faces           Mass flow
---------------------------------------------------------------
Entree                    2        2064         0.452920094E-02
Paroi lisse               5       54798         0.173905083E-20
Paroi rugueuse            6           0         0.000000000E+00
Symetrie                  4           0         0.000000000E+00
Sortie libre              3          44        -0.452920104E-02
Indefini                  1           0         0.000000000E+00
---------------------------------------------------------------
 
 
Should I change the velocity of INFILTRATION from 0.446 to -0.446 m/s?
Any other suggestion?
 
Thanks,
 
Axel Cablé
 

[David Monfort]

Hi Axel,
Concerning your first question about a proper stop of the calculation (or an increase of the number of time-step), you are close to the solution! Here is the right way to this:
<blank line>
1200
As for your second question, could you post either your XML file or your usclim.f90 file so that I can have a look at it ? This is indeed a strange behavior...
David

[Axel Cablé]

Hi David, thanks for your answer the calculation stops properly now.

As for the mass flow, here is the xml file of the case I currently study, where a negative speed is imposed. The characteristics of the geometry are:

INLET: S=0.0015m², U=-2.77 m/s, Flow= A = -0.486E-2 kg/s
INFILTRATION: S=0.0028m², U=0.446 m/s, Flow= B = 0.146E-2 kg/s
(see the attached schema)

I get:

Boundary type          Code    Nb faces           Mass flow --------------------------------------------------------------- Entree                    2        1554        -0.636902676E-02 Paroi lisse               5       49769         0.153126584E-21 Paroi rugueuse            6           0         0.000000000E+00 Symetrie                  4           0         0.000000000E+00 Sortie libre              3          45         0.636918167E-02 Indefini                  1           0         0.000000000E+00 ---------------------------------------------------------------

ie (A-B) for the total incoming mass flow, and (A+B) for the total outgoing mass flow, does it seem ok to you?

Also, I have set a free outlet condition for OUTLET. Hence I'm forced to impose either a zero flux or an imposed value for my scalar: temperature. However, I would like the fluid to "carry" the heat out of the room. Should I use a non standard boundary condition in usclim.F (flux condition)?

Thanks in advance for your answer,

Axel

[David Monfort]

Hello Axel,
The results seem fine to me. Mass fluxes are always taken negative for inlets (u.n < 0 where n is the boundary face normal, always oriented towards the exterior) and positive for outlets (u.n > 0).
Concerning the oulet condition, I would advise you to first test with the standard condition: the velocity will indeed "carry" the heat out of the room except if you have backward flow (the behavior is then a bit more complex... see e.g. the comments at the beginning of the usclim.F subroutine.).
David