Supersonic Convergence

beschadigunc · June 1, 2022, 10:21

Hi guys im pretty new here and also relatively new into CFD ,

I have been having some question marks regarding my convergence .

So the current sim that im running at the cluster has 97 Millon cells and I believe a pretty good mesh the wally values are between 0.5 and 3.8 also has grid sequencing initialization.

it is a rocket running at mach 1.2 and I used 25/mach for CFL number. It is running in freestream which has enough gap to propagate the pressure.

But with all these I get this kind of residuals even though the values converge to something Im not sure if the results are reliable or not nor was I able to find some reference wind tunnel paper so that I can check my physics .

image :

https://ibb.co/BN8WV1Z

Should I post it somewhere else ?

aerosayan · June 1, 2022, 15:08

Your image link is not working. Had to guess the real URL. This one works : https://imgbb.com/BN8WV1Z

Experts can see the image and help you now.

beschadigunc · June 1, 2022, 19:01

Quote:

Originally Posted by aerosayan

Your image link is not working. Had to guess the real URL. This one works : https://imgbb.com/BN8WV1Z

Experts can see the image and help you now.

Thanks mate

JBeilke · June 2, 2022, 08:36

Residuals don't tell you, if a simulations gives correct results.
Your residuals look not bad. Probably you just need some more iterations (maybe 2000)
CCM+ usually gives you normalised residuals. So you only see, that they go down (or do something esle). Go to "Monitors ..." and switch off the normalisation to get the absolute values.

June 1, 2022, 10:21	Supersonic Convergence	#1
beschadigunc New Member Icant Join Date: Jun 2022 Posts: 3 Rep Power: 4	Hi guys im pretty new here and also relatively new into CFD , I have been having some question marks regarding my convergence . So the current sim that im running at the cluster has 97 Millon cells and I believe a pretty good mesh the wally values are between 0.5 and 3.8 also has grid sequencing initialization. it is a rocket running at mach 1.2 and I used 25/mach for CFL number. It is running in freestream which has enough gap to propagate the pressure. But with all these I get this kind of residuals even though the values converge to something Im not sure if the results are reliable or not nor was I able to find some reference wind tunnel paper so that I can check my physics . image : https://ibb.co/BN8WV1Z Should I post it somewhere else ?

June 2, 2022, 08:36		#4
JBeilke Senior Member Joern Beilke Join Date: Mar 2009 Location: Dresden Posts: 528 Rep Power: 20	Residuals don't tell you, if a simulations gives correct results. Your residuals look not bad. Probably you just need some more iterations (maybe 2000) CCM+ usually gives you normalised residuals. So you only see, that they go down (or do something esle). Go to "Monitors ..." and switch off the normalisation to get the absolute values. aerosayan likes this.

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June 1, 2022, 15:08		#2
aerosayan Senior Member Sayan Bhattacharjee Join Date: Mar 2020 Posts: 495 Rep Power: 8	Your image link is not working. Had to guess the real URL. This one works : https://imgbb.com/BN8WV1Z Experts can see the image and help you now.