an odd behavior on continuity error

immortality · July 5, 2013, 15:37

continuity error is being displayed in some time after 0 time instead of begining the run as is shown.what may be wrong with continuity error?

wyldckat · July 7, 2013, 10:27

Why do you think it's odd? It seems perfectly fine to me.

The values are all very small and it's somewhat indicative that the flow is going back and forth, leading to the cumulative errors to go back and forth as well.

immortality · July 20, 2013, 12:56

Hi
it seems it doesn't solve continuity equation when residuals are a horizontal line.

wyldckat · July 21, 2013, 05:15

Hi Ehsan,

Mmm... without a test case, and from the looks of the graph, my guess is that the continuity errors are below the floating point resolution (http://en.wikipedia.org/wiki/Machine_epsilon) for the first several iterations.

I vaguely remember seeing very low values for one of the solvers where I added the continuity calculation, at your request. I found it odd, but I assumed it would always be so low and it was why it was not originally present in the solver.
In other words, either the continuity calculation was not necessary for the solver in question or something might be missing in the continuity equation.

Best regards,
Bruno

July 7, 2013, 10:27		#2
wyldckat Retired Super Moderator Bruno Santos Join Date: Mar 2009 Location: Lisbon, Portugal Posts: 10,975 Blog Entries: 45 Rep Power: 128	Why do you think it's odd? It seems perfectly fine to me. The values are all very small and it's somewhat indicative that the flow is going back and forth, leading to the cumulative errors to go back and forth as well. __________________ OpenFOAM: FAQ \| Getting started Forum: How to get help, to post code/output and forum guide Read this before sending me PM

July 20, 2013, 12:56		#3
immortality Senior Member Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,208 Rep Power: 26	Hi it seems it doesn't solve continuity equation when residuals are a horizontal line. __________________ Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked.

July 21, 2013, 05:15		#4
wyldckat Retired Super Moderator Bruno Santos Join Date: Mar 2009 Location: Lisbon, Portugal Posts: 10,975 Blog Entries: 45 Rep Power: 128	Hi Ehsan, Mmm... without a test case, and from the looks of the graph, my guess is that the continuity errors are below the floating point resolution (http://en.wikipedia.org/wiki/Machine_epsilon) for the first several iterations. I vaguely remember seeing very low values for one of the solvers where I added the continuity calculation, at your request. I found it odd, but I assumed it would always be so low and it was why it was not originally present in the solver. In other words, either the continuity calculation was not necessary for the solver in question or something might be missing in the continuity equation. Best regards, Bruno immortality likes this. __________________ OpenFOAM: FAQ \| Getting started Forum: How to get help, to post code/output and forum guide Read this before sending me PM

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