High amount of Artificial energy in Eulerian Mesh

[Teru1212]

Hello,

Im doing a Bird strike with a Eulerian Mesh. Everything works fine, I have a box with Eulerian Elements and define an EOS and a Bird Geometry. I "shoot" the bird on a Steel PLate to lateer get the PRessure curve. I am also looking at the Energies. I know that, when you use Lagrange, there is hourglassing that you can see by plotting Artificial Energy ALLAE in the history output. So far so good, when i use Lagrange the ALLAE is there and very big, which makes sense because of the distortion of the lagrangian mesh and therefore hourglassing.

Now with CEL, I also get ALLAE that is bigger than expected (Usually like 8% of the TOTAL ENERGY). I thought that there would be much less to no ALLAE because in Euler there shouldnt be hourglassing or severe Mesh distortion, or am I wrong? When I compare my Results to other reasearches there I can barely see the ALLEA when they plot the energy curve.

TLDR: Is it normal to get high amounts of ALLAE when using CEL/Euler Elements in Bird strike/Impact Simulation? OI not, how can I fix this?.

Best Regards and thanks for you answers!

 

[FEA way]

Indeed, ALLAE can be large in CEL analyses. To avoid this you can reduce the scaling factor for hourglass stiffness (using *SECTION CONTROLS) but, generally speaking, it’s often not recommended to use energy balance as a main factor when verifying the results of CEL analyses.

 

[Teru1212]

Thanks, I always thought there was no hourglassing in CEL because there is no mesh distortion. WHat can I use to verify the results? I thought Etotal ist a good indicator because of loss in mass. And ALLAE as well like in Lagrange but now im confused.

 

[FEA way]

If you have access to Dassault Systemes Knowledge Base, check the article "Best Practices for Bird Strike Simulations with Abaqus/Explicit".

 

[Teru1212]

I have acces via my uni mail. But I cant find the article in the kowledge base.

 

[FEA way]

Unfortunately, it seems that a customer account is needed to access this article. However, the comprehensive pdf document associated with it can be found also in the 3DSwym SIMULIA Community.

 

[Teru1212]

Thank you, I Found it, this is very helpful