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A Study on the Multi-Material ALE Scheme with FSI in LS-DYNA

A Study on the Multi-Material ALE Scheme with FSI in LS-DYNA. Rudolf Bötticher TMB GmbH www.rudolf-boetticher.de . Motivation. Assess time step dependence of multi-material ALE (ELFORM=11) results for the two advections schemes with a FSI interface present. 1. Airbag - Random Error

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A Study on the Multi-Material ALE Scheme with FSI in LS-DYNA

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  1. A Study on the Multi-Material ALE Scheme with FSI in LS-DYNA Rudolf BötticherTMB GmbH www.rudolf-boetticher.de 

  2. Motivation • Assess time step dependence of multi-material ALE (ELFORM=11) results for the two advections schemes with a FSI interface present . • 1. Airbag - Random Error • 2. Water Jet – Troubles & Monitoring • 3. Duct – Leakage • 4. Conclusions www.rudolf-boetticher.de

  3. Tested this on 9th May 2007 with ls971_s_11220_winx64_p on the same machine: the effect has vanished!!! Caution: random error! Rerun input deck with *AIRBAG_ALE five times each for no-switching (UP), switching and ALE METH=1, and switching and ALE METH=2 and for two settings of the time step (TSSFAC) 32 bit single precision 5434a SMP (s_5424a_p) on dual Opteron with Windows x64 Is a LS-DYNA solver run always a deterministic function evaluation? www.rudolf-boetticher.de

  4. Airbag pressure www.rudolf-boetticher.de

  5. METH=1 - Donor Cell Scheme • - TSSFAC=0.5 • - TSSFAC def. www.rudolf-boetticher.de

  6. METH=2 - v. Leer Scheme • - TSSFAC=0.5 • - TSSFAC def. www.rudolf-boetticher.de

  7. Troubles: • Inter-ALE-material interfaces • Interface tracking near FSI with three fluids • Re-appearance of ALE-materials LS-PrePost SelPar tick Fluid box www.rudolf-boetticher.de

  8. FSI: tweaking of *CONSTRAINED_LAGRANGE_IN_SOLID (CLIS) Ongoing development 5434a and beyond: always use the newest version for consistency and efficiency! TSSFAC NADV METH CTYPE DIREC PFAC ILEAK www.rudolf-boetticher.de

  9. FSI-interface energy dependent on time step, which is more important than advection method Monitoring of interface advancing www.rudolf-boetticher.de

  10. User-specified penalty stiffness and leakage control important www.rudolf-boetticher.de

  11. Modeling • Intelligent grouping of inter-ALE-material and ALE-material to Lagrangian interfaces. • Individual penalty stiffness. New treatment of initial FSI-penetration on CLIS. Water Soft tissue EFG No hourglass energy! Air www.rudolf-boetticher.de

  12. No time step dependence anymore as compared to investigation in 2004 EFG www.rudolf-boetticher.de

  13. Water Air Air TSSFAC=0.6 TSSFAC=0.3 www.rudolf-boetticher.de

  14. DIREC=6 sp dp www.rudolf-boetticher.de

  15. Conclusions • The strong influence of the parameters on CLIS in conjunction with the time step on the creation of non-physical interface energy may yield low quality results. • Random error with multiple CPUs! • Advection scheme less important. www.rudolf-boetticher.de

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