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Radioss solver Error % Control

AJM

Hello,

Could anyone tell what are other possibilities that we can control on Error percentage apart from penetration and intersection in radioss explicit simulation.

in my model i dont see any penetration and intersection but still end up with error% 99.9

Thank you

CYCLE TIME TIME-STEP ELEMENT ERROR I-ENERGY K-ENERGY T K-ENERGY R EXT-WORK MAS.ERR

3433 0.1365E-02 0.4000E-06 NODE 9881 99.9% 0.2593E-01 0.1915E-04 0.000 0.3501E-05 0.4209

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Pranav Hari

Hi AJM

If the error is positive, there is an energy creation. If the positive energy error is high, the source of this energy has to be identified. Normally, the energy error must be negative and decreasing (except for the first cycle ).

The possible reasons for high energy error are:

Incompatible Kinematic Conditions

Timestep too low because of mesh size or high interface penetrations/distortions in the structure.

Please check these forum posts where the energy errors were resolved earlier.

https://community.altair.com/community?id=community_question&sys_id=6fa600ba1b2bd0908017dc61ec4bcb58

https://community.altair.com/community?id=community_question&sys_id=485644b61b2bd0908017dc61ec4bcbba

https://community.altair.com/community?id=community_question&sys_id=6596807a1b2bd0908017dc61ec4bcbde

Please share the model if the issue persist.

Thanks

AJM

Hello Pranav,

Thanks for the previous replay with explanation.

I would like to know further more about Error % .

when we go for advance mass scale option, it will be 2% or lesser will be advised to use. though i keep mass error percentage bellow than 1% safer side, i would end up with % error 99.9 which is almost diverged.

could you explain how to tackle % error when AMS will be added .

Thanks in advance

Simon Križnik

Hi @AJM

from Radioss help (see attached document):

Any targeted model for AMS application should run first in /DT/NODA/CST with a reasonable energy error (ERROR < +2%) and acceptable added mass (MAS.ER < 0.02) along its simulation time. A model unable to run with /DT/NODA/CST will not run with AMS either.

Output the number of AMS iterations per cycle via /DT/AMS/Iflag - Iflag =2 may help monitoring convergence quality at no extra CPU cost.

Maximum allowed iterations before the divergence stops is 1000. 75 to 100 iteration per cycle is a sign of a poor convergence 50 still may provide some speedup

30 iterations or less is considered a good convergence.

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