Recent updates done to libforces
Good day,
I'm very impressed with the new updates that were done in libforces / the ability to use constraints and restraints is very interesting. I just have a simple suggestion regarding the springs. With the report option "on", the spring lengths and angles are displayed. However, I understand that the magnitude is returned, meaning that the values are always > 0. It would be a good thing if the "sign" would be included as well / it makes it easier to track the exact position in time of the rigid body. Regards, PO |
Hello,
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What to do with the sign of the angle was unambiguous, but linear springs can start with zero length and move in any direction, so the concept of a sign for their displacement is not always clear. I added reporting of the vector from the anchor to the instantaneous attachment point on the body. Graham |
Thanks for the changes / will give it a try.
Another question -> did you try to run a case with single cpu for some time and then, decompose the latest time step for a multi-cpu run ? I most be missing something because I just cannot run multi-cpu if I try that. I guess I need to move the latest time/polyMesh/points file in constant/polyMesh before decomposing or something like that ... Not sure what is the best practice for this. Regards, PO |
There are some issues to do with decomposing moving mesh cases in 1.6.x that have been fixed in our internal development version.
For the moment, best practice would be to decompose the case at the start and do everything in parallel. Graham |
Ok, thanks Graham
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Good day Graham,
I have another question related to the definition of the damping for the restraints. Can you confirm that the damping input is in fact the damping ratio, in percentage, meaning that an input of 0.5 means 0.5% damping ratio (or 0.005). Also, can you confirm that this works for both axial spring and vertical spring / I'm facing some discrepancies in my decay tests. Regards, PO |
It is not a damping ratio, it is a damping coefficient.
For the definition see linearSpring.H Code:
//- Damping coefficient (Ns/m) Code:
restraintForce = -stiffness_*(magR - restLength_)*r - damping_*(r & v)*r; |
Some results
Hi I made some fsi videos using pimpleDyMFoam, but quite rudiment, It is a wind tunnel case. I found the new patch is very capable for some rigid body movement simulation, Good.
Video Link |
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