a study on the multi-material ale scheme with fsi in ls-dyna rudolf bötticher tmb gmbh
TRANSCRIPT
A Study on the Multi-Material ALE Scheme with FSI
in LS-DYNA
Rudolf BötticherTMB GmbH
www.rudolf-boetticher.de
Bonn, 10.11.2005 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
2. Water Jet – Troubles & Monitoring
3. Duct – Leakage
4. Conclusions
Bonn, 10.11.2005 www.rudolf-boetticher.de
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?
Tested this on 9th May 2007 with ls971_s_11220_winx64_p on the same machine:
the effect has vanished!!!
Bonn, 10.11.2005 www.rudolf-boetticher.de
Airbag pressure
Bonn, 10.11.2005 www.rudolf-boetticher.de
- TSSFAC=0.5
- TSSFAC def.
METH=1 - Donor Cell Scheme
Bonn, 10.11.2005 www.rudolf-boetticher.de
- TSSFAC=0.5
- TSSFAC def.
METH=2 - v. Leer Scheme
Bonn, 10.11.2005 www.rudolf-boetticher.de
• Inter-ALE-material interfaces
• Interface tracking near FSI with three fluids
• Re-appearance of ALE-materials
Troubles:
LS-PrePost
SelPar
tick Fluid box
Bonn, 10.11.2005 www.rudolf-boetticher.de
FSI: tweaking of *CONSTRAINED_LAGRANGE_IN_SOLID
(CLIS)
TSSFACNADV
METHCTYPE
DIRECPFACILEAK
Ongoing development 5434a and beyond: always use the newest version for consistency and efficiency!
Bonn, 10.11.2005 www.rudolf-boetticher.de
FSI-interface energy dependent on time step, which is more important than advection method
Monitoring of interface advancing
Bonn, 10.11.2005 www.rudolf-boetticher.de
User-specified penalty stiffness and leakage control important
Bonn, 10.11.2005 www.rudolf-boetticher.de
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 tissueEFGNo hourglass energy!
Air
Bonn, 10.11.2005 www.rudolf-boetticher.de
No time step dependence anymore as compared to investigation in 2004
EFG
Bonn, 10.11.2005 www.rudolf-boetticher.de
Water
Air
Air
TSSFAC=0.6 TSSFAC=0.3
Bonn, 10.11.2005 www.rudolf-boetticher.de
DIREC=6
sp dp
Bonn, 10.11.2005 www.rudolf-boetticher.de
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.