Access error while solving stops simulation

SMagee · July 15, 2015, 10:25

I'm having some strange error on Ansys 15.0.7 Fluent. After exactly 16 iterations the following messages stop the simulation:

Error: access: unbound variable
Error Object: get-head

I can resume the simulation and it advances an other 16 iterations, failing with the same error.
I haven't found any information about this error does anyone know what could be the cause and how to fix it?

ptemp · February 13, 2017, 09:56

Were you ever able to resolve this issue? I'm running on Fluent 17.1 and get the same two error messages after a few hundred iterations.

SMagee · February 13, 2017, 11:42

I seem to recall that I was able to solve this issue just by starting from scratch the fluent simulation.
It was a bit of pain to have to introduce all the input data again but the simulation worked. It must be caused by some corruption of the file.

On the other hand this was 2 yr ago, so I'm not sure if this is really what happened.

LuckyTran · February 15, 2017, 01:29

I ran into this problem a few times and it was also caused by a corrupted .cas file. The only way to fix it was to completely start over. The most recent time was also 2 years ago for me, in the era of Fluent v15, but I would not be surprised if it happened again.

I tried re-importing the mesh and starting a new case file. Then I wrote all the settings from the old corrupted case file and then reading those settings into the new case, but it still crashed. Somehow Fluent can sometimes lose track of its settings in the case file. It is probably something really dumb like a missing character in the .cas file (like a missing { or }), but unless you are a master of reading .cas files there's not much you can do. One also usually writes them in binary. =(

It's not a big loss if you have a .jou file to setup your case, but it can be really annoying if you don't.

Kokemoor · May 2, 2017, 11:58

I'm getting this error too, in 17.0, with a setup created by an ACT wizard (functionally similar to running a journal). Starting fresh and rerunning the wizard doesn't fix it. Mine is clearly related to the convergence criteria. I have two monitors used to judge convergence, and they look at the past 50 iterations. If both are enabled, it breaks with the unbound variable get-head error on iteration 51, but if either one alone is enabled, it works just fine.

One criterion is mostly dominated by the other, so I wouldn't lose that much to switch to just one criterion, but it's a weird error, and I've never had this problem setting things up manually. Any thoughts?

July 15, 2015, 10:25	Access error while solving stops simulation	#1
SMagee New Member Sebastian Magee Join Date: Jul 2015 Posts: 5 Rep Power: 11	I'm having some strange error on Ansys 15.0.7 Fluent. After exactly 16 iterations the following messages stop the simulation: Error: access: unbound variable Error Object: get-head I can resume the simulation and it advances an other 16 iterations, failing with the same error. I haven't found any information about this error does anyone know what could be the cause and how to fix it?

February 13, 2017, 11:42		#3
SMagee New Member Sebastian Magee Join Date: Jul 2015 Posts: 5 Rep Power: 11	I seem to recall that I was able to solve this issue just by starting from scratch the fluent simulation. It was a bit of pain to have to introduce all the input data again but the simulation worked. It must be caused by some corruption of the file. On the other hand this was 2 yr ago, so I'm not sure if this is really what happened. ptemp likes this.

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February 13, 2017, 09:56		#2
ptemp New Member Paul Join Date: Feb 2017 Posts: 13 Rep Power: 9	Were you ever able to resolve this issue? I'm running on Fluent 17.1 and get the same two error messages after a few hundred iterations.

February 15, 2017, 01:29		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,763 Rep Power: 66	I ran into this problem a few times and it was also caused by a corrupted .cas file. The only way to fix it was to completely start over. The most recent time was also 2 years ago for me, in the era of Fluent v15, but I would not be surprised if it happened again. I tried re-importing the mesh and starting a new case file. Then I wrote all the settings from the old corrupted case file and then reading those settings into the new case, but it still crashed. Somehow Fluent can sometimes lose track of its settings in the case file. It is probably something really dumb like a missing character in the .cas file (like a missing { or }), but unless you are a master of reading .cas files there's not much you can do. One also usually writes them in binary. =( It's not a big loss if you have a .jou file to setup your case, but it can be really annoying if you don't.

May 2, 2017, 11:58		#5
Kokemoor Senior Member Andrew Kokemoor Join Date: Aug 2013 Posts: 122 Rep Power: 14	I'm getting this error too, in 17.0, with a setup created by an ACT wizard (functionally similar to running a journal). Starting fresh and rerunning the wizard doesn't fix it. Mine is clearly related to the convergence criteria. I have two monitors used to judge convergence, and they look at the past 50 iterations. If both are enabled, it breaks with the unbound variable get-head error on iteration 51, but if either one alone is enabled, it works just fine. One criterion is mostly dominated by the other, so I wouldn't lose that much to switch to just one criterion, but it's a weird error, and I've never had this problem setting things up manually. Any thoughts?