Learning Forum

[Reno Genest]

Hello Arnaud,

Which LS-DYNA version are you using?

Are you able to reproduce the problem with the cylinder flow example?

Basics : Cylinder flow — Welcome to LS-DYNA Examples

LSTC QA Test Case Documentation: LSTC-QA-LS-DYNA-ICFD-VAL-3.1-1 (dynaexamples.com)

 

Do you see different fluid pressure contour plots with different incoming fluid velocities? The pressure drag force is calculated from the pressure as follows:

Have you tried with *ICFD_BOUNDARY_FEESLIP around the body? The ICFD training says the following:

"Warning : in some cases where friction drag is not fundamental, modeling a solid wall
using a free slip condition can give better numeric results than a non slip boundary
condition with a bad quality mesh (incorrectly capturing the boundary layer can lead
to over constrains in the pressure field of the flow)."

 

Give it a try and let me know how it goes.

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Reno.