Author Topic: Lysmer in 2D vs 3D  (Read 12245 times)

Dr. Ahmad Chihadeh

  • Jr. Member
  • **
  • Posts: 13
Lysmer in 2D vs 3D
« on: August 07, 2024, 03:43:12 AM »
Dear Colleagues,

I run example similar to the one provided here (http://feap.berkeley.edu/wiki/index.php?title=Lysmer-Kuhlemeyer), in 2D and in 3D.
However in 3D the result is not as good as in 2D. Note that I added a multiply by 'xsj' on  the definition of 'shpab'.
I attached the input files and the result.

Best regards,
Ahmad

Dr. Ahmad Chihadeh

  • Jr. Member
  • **
  • Posts: 13
Re: Lysmer in 2D vs 3D
« Reply #1 on: August 07, 2024, 05:32:21 AM »
I think this is because in 3D, xsj is multiplied by facp and facs

!         Velocity factors
          facp = d(15)*d(3)*d(11)*xsj    ! a*rho*V_p
          facs = d(16)*d(3)*d(12)*xsj    ! b*rho*V_s


and then it is also mutiplied by qq

!         Flux
          qq( : ) = (aa(:,1)*vv(1) + aa(:,2)*vv(2) + aa(:,3)*vv(3))*xsj

Prof. R.L. Taylor

  • Administrator
  • FEAP Guru
  • *****
  • Posts: 2647
Re: Lysmer in 2D vs 3D
« Reply #2 on: August 07, 2024, 01:17:53 PM »
I would suggest doing a 2-d like problem with a 3-d slice to find the possible coding error.

Prof. R.L. Taylor

  • Administrator
  • FEAP Guru
  • *****
  • Posts: 2647
Re: Lysmer in 2D vs 3D
« Reply #3 on: August 07, 2024, 02:05:43 PM »
Sorry after looking at your input files that is what you did.

There seems to be an extra xsj in the 3-d.  I removed the 'xsj' off the face & face terms and seem to get the same answer with both your files.   Hopefully this will help you.

Prof. R.L. Taylor

  • Administrator
  • FEAP Guru
  • *****
  • Posts: 2647
Re: Lysmer in 2D vs 3D
« Reply #4 on: August 07, 2024, 02:20:47 PM »
One other thing.  You should not need a MASS matrix in your batch file unless you are doing an Eigen analysis or an explicit time analysis.  For fear elements you can set the mass type in the MATErial set data.

Dr. Ahmad Chihadeh

  • Jr. Member
  • **
  • Posts: 13
Re: Lysmer in 2D vs 3D
« Reply #5 on: August 07, 2024, 11:32:58 PM »
Thank you Professor.
regarding the MASS, if I delete

MASS,CONSistent

from the input file, it does not work and I get

-> ERROR: ABC can not be used in static analysis

although there is still

BATC
TRANS,NEWM, 0.25, 0.5
END

in the input file.

Prof. R.L. Taylor

  • Administrator
  • FEAP Guru
  • *****
  • Posts: 2647
Re: Lysmer in 2D vs 3D
« Reply #6 on: August 17, 2024, 09:23:20 AM »
The need to include the MASS is a bug that will be corrected in the next release.