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

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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.