CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   OpenFOAM Running, Solving & CFD (http://www.cfd-online.com/Forums/openfoam-solving/)
-   -   Simulationtime for scalarTransportFoam (http://www.cfd-online.com/Forums/openfoam-solving/112305-simulationtime-scalartransportfoam.html)

despaired student January 25, 2013 13:19

Simulationtime for scalarTransportFoam
 
Hi,

I've just a short question about scalarTransportFoam.
There are no eddys, turbulences or other transient parts in my velocity field. Now I'm simulating the distribution of a scalar in this velocity-field. The question ist when to stop the simulation? I thought about:

a) measure the scalar-input and -output. When conservation of mass is reached then stop the simulation. If this is correct how would you justify this as the criterium to stop at?

b) make sample-pictures at different time-steps. When there are no changes in the sample-pictures of the concentration field one can say that the simulation should be stoped.

c) measure the way a scalar moves from inlet to outlet. Divide this way by the velocity (average velocity or something like this) and then you get the timestep to that you have to run the simulation.

Could you give me a short feedback/comment...the answer to my initial question is also welcome :)


Cheers

fumiya January 25, 2013 21:54

Hi,

If your velocity field is steady, I think the scalar distribution reaches a steady
state at some time. You can monitor the time history of scalar distributions at
some points using the probes function and stop simulation when variations
become smaller than your criterion. I think you can estimate the approximate
time needed to reach steady state by the method you wrote in c.

Hope that helps,
Fumiya

despaired student January 26, 2013 16:05

Hi fumiya,

thanks for your reply. You are right the probe utility should work fine in my case...haven't thought about it...my bad :)


regards


All times are GMT -4. The time now is 14:22.