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rastgar650

Advanced mass scaling

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Hi,

 

I have a simulation which crashes after a while due to error ID 205 and 207 ("ENERGY ERROR LIMIT REACHED" and "TOTAL MASS ERROR LIMIT REACHED"). I have tried to change mass scaling value, but nothing happened. my first question is what would be the reason of crash? Does it come from fast loading or caused by changing material properties to less stiff behavior?

Moreover, I tried to use AMS, but ran into an error:

ERROR ID :           55
** ERROR IN INPUT FORMAT
DESCRIPTION :
   -- OPTION : AMS
   -- BLOCK : /PROP/SHELL/20
   -- LINE : /END

It should be noted that /AMS is in the _0000.rad file and /DT/AMS  .67 .5E-3 in the 0001.rad (Engine).

 

 

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Hi,

The energy error percentage is the parameter that checks the energy conservation during each numerical cycle. This is a measure of the quality of an explicit dynamic simulation. This parameter defines the maximum allowed value of energy error before killing the simulation.It is bounded to + or - 99%.

From the engine out (_0001.out) file check what is contributing for this high energy error and rectify the same. This can cause the time step to drop which will finally result in run termination with error messages  ERROR LIMIT REACHED" and TOTAL MASS ERROR LIMIT REACHED. 

The format for /AMS described above is fine. If you can share the model we will review the same.

Meanwhile I'm sharing a model file with /AMS option used. Please make sure that the format is followed similarly. 

 

energy_error.PNG

 

EXAMPLE4_66_0000.rad.zip

 

EXAMPLE4_66_0001.rad.zip

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Hi,

The simulation happening in each cycle is represented here. NC is the number of cycle, T is the solution run time, DT is the time step and DM/M shows the mass error.

When a user impose a time step in the model, mass will be added to the system. And DM/M shows the mass added to the system.

As a good practice the mass error in the model should be than .05 (5%).

 

ank likes this

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NC=   39000 T= 4.0609E-03 DT= 1.0172E-07 ERR= -0.4% DM/M= 3.2024E-06 ?

 

Is it ok for a simulation ?

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NC=15300000 T= 1.5300E+00 DT= 1.0004E-07 ERR=-87.7% DM/M= 8.8558E-01

 

 

Is this is bad ?What consequence it can result ?

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Hi,

The number of cycles of this run seems to very high, that is it seems like you are running this model for a long time.

Mass added (DM/M) is also bit higher, as the recommended mass error is less than 5% ie .05. 

ank likes this

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