Convergence problem

SarahIb · June 12, 2018, 08:28

Hey,

I'm trying to launch a simulation with a moving piston and valves (using udf) the problem is that I always have a temperature and pressure divergence.
I've tried to change the parametres in the solution control but the problem remain the same.
Is there other solution for my problem .

Ps : i checked the quality mesh and the udf are correct.
You can see the attached files for more details about the simulation.
Please help.

Time step : 0.00001

RaiderDoctor · June 12, 2018, 11:50

Your time step seems very small. This may be causing your solution to diverge, have you adjusted this to see if it helped?

SarahIb · June 13, 2018, 04:32

I can't go any higher than 0.00001 due to my dymanic mesh and moving parts, if so i get a negative volume. anyone else has a suggestion ?

SarahIb · June 13, 2018, 06:08

My factors : Divergence.PNG

My job with the calcul : job_fluent_sarah.c

Thank's!

RaiderDoctor · June 13, 2018, 14:28

So long as you set your dynamic mesh conditions correctly, you pretty much take as large as a time step as you want. The file you posted is your output file from fluent?

If you are using advanced settings, I may be outside my realm of knowledge haha.

Could you post an image of your dynamic mesh settings? Also, is there anyway you post your case and data for your setup? Maybe we can have a look.

SarahIb · June 21, 2018, 06:30

Hi,

The file i sent is the journal from my calcul from the cluster.

You can see here the settings from dynamic mesh :
capture1.PNG
Capture2.PNG
Capture3.PNG

I can't send the case, the size doesn't fit here.

June 12, 2018, 08:28	Convergence problem	#1
SarahIb New Member Join Date: Jun 2018 Posts: 4 Rep Power: 8	Hey, I'm trying to launch a simulation with a moving piston and valves (using udf) the problem is that I always have a temperature and pressure divergence. I've tried to change the parametres in the solution control but the problem remain the same. Is there other solution for my problem . Ps : i checked the quality mesh and the udf are correct. You can see the attached files for more details about the simulation. Please help. Time step : 0.00001

June 12, 2018, 11:50		#2
RaiderDoctor Senior Member Join Date: Dec 2016 Posts: 152 Rep Power: 10	Your time step seems very small. This may be causing your solution to diverge, have you adjusted this to see if it helped? SarahIb likes this.

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June 13, 2018, 04:32		#3
SarahIb New Member Join Date: Jun 2018 Posts: 4 Rep Power: 8	I can't go any higher than 0.00001 due to my dymanic mesh and moving parts, if so i get a negative volume. anyone else has a suggestion ?

June 13, 2018, 06:08		#4
SarahIb New Member Join Date: Jun 2018 Posts: 4 Rep Power: 8	My factors : Divergence.PNG My job with the calcul : job_fluent_sarah.c Thank's!

June 13, 2018, 14:28		#5
RaiderDoctor Senior Member Join Date: Dec 2016 Posts: 152 Rep Power: 10	So long as you set your dynamic mesh conditions correctly, you pretty much take as large as a time step as you want. The file you posted is your output file from fluent? If you are using advanced settings, I may be outside my realm of knowledge haha. Could you post an image of your dynamic mesh settings? Also, is there anyway you post your case and data for your setup? Maybe we can have a look.

June 21, 2018, 06:30		#6
SarahIb New Member Join Date: Jun 2018 Posts: 4 Rep Power: 8	Hi, The file i sent is the journal from my calcul from the cluster. You can see here the settings from dynamic mesh : capture1.PNG Capture2.PNG Capture3.PNG I can't send the case, the size doesn't fit here.