What kind of error?

Mark_89 · August 24, 2013, 06:15

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)

August 24, 2013, 06:15	What kind of error?	#1
Mark_89 New Member Marco Join Date: Aug 2013 Posts: 13 Rep Power: 12	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

September 1, 2013, 05:01		#5
Mark_89 New Member Marco Join Date: Aug 2013 Posts: 13 Rep Power: 12	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? Last edited by Mark_89; September 1, 2013 at 17:47.

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August 26, 2013, 03:12		#2
Roman Member Roman Join Date: Mar 2011 Posts: 46 Rep Power: 15	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?

August 29, 2013, 17:16		#3
Mark_89 New Member Marco Join Date: Aug 2013 Posts: 13 Rep Power: 12	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

August 30, 2013, 02:34		#4
Roman Member Roman Join Date: Mar 2011 Posts: 46 Rep Power: 15	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!

September 2, 2013, 02:43		#6
Roman Member Roman Join Date: Mar 2011 Posts: 46 Rep Power: 15	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)