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Mark_89 August 24, 2013 06:15

What kind of error?
Hi, when i use star ccm+ to simulate the combustion process with an injector, the software says "Mass Fractions of the species are nonpositive" as soon as i run the simulation. What can i do to solve the problem?
Probably it's a problem of the injector. Can someone help me, please?
thank you :)

Roman August 26, 2013 03:12

What parameters did you set for Physics Values -> Volume Fractions parameter on your injectors? How many phases do you simulate with? Did you also check your inlet and outlet conditions and what volume fractions are set there?

Mark_89 August 29, 2013 17:16

Oh, I've resolved the probelm. As you said, it was a problem of phases. I've forgot to write the volume fraction at outlet (0.233 fraction of Oxygen and 0.767 of Nitrogen).
Thank you for your help.
At the moment I would calcolate heat release profile. What is the field function that i have to report? how can i export just the final value of the last iteration for each timestep to know the heat quantity released at every timestep?
thank you, again :)

Roman August 30, 2013 02:34

That great to hear. There are several ways to export heat profile data. You could create a report on the region boundary it self and plot it out pr timestep which you then could export as a .csv file. Alternative would be to create a section plane derived part at the profile, create a scalar scene and plot the field function on it, you could then setup the scene to auto export plot images pr time step into a folder and you would get some nice, colorful time progression plots.

As for what Field Function you should use, I have no clue. I would perhaps export several of them and do an analysis afterwords of what is worth keeping. Take a look at the user guide and search for "Heat Transfer Field Functions Reference", that should at least get you started!

Mark_89 September 1, 2013 05:01

Ok, I'm tried to do that you can said me before, but unfortunatelly it seems that star ccm+ exports just per iteration and not per time step. Maybe there is something that i've forgot. When I create a plot, I impose sclar "time step" on x-axes, and my report value on y-axes. Then I change update frequency from iterations to time step. Is there something that I'v forgot?? When I run for two timesteps, if I tabulate and export, I expect to find just two values ; instead i see a lot of values, each one with the same time step (4E-5). Where is the problem?

Roman September 2, 2013 02:43

You will have to setup autoexport (a check box option), for each time step. Problem is, Star will only export your results for your current time step (unless you set up a report w/ monitor and plot of a value, then it tracks that values progress), so the solution is to get star to export your values for each time step. This way you will get a new CSV file for each timestep that you could combine in Matlab/ Scilab/ Mathematica etc.

The option you are looking for is under Scene/ Table -> Attributes -> Update -> Checkbox for Save to File. (Or so I remember from the top of my head)

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