CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Programming & Development

traction calculation in fsiFoam

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Search this Thread Display Modes
Old   June 12, 2019, 10:42
Default traction calculation in fsiFoam
New Member
Join Date: Jan 2017
Posts: 1
Rep Power: 0
fuxpaul is on a distinguished road
Hello everyone,

i have been reading a lot of threads/post in this forum and it was a LOT of help so far. So thank everyone contributing to this forum.

I have been working with foam-extend-v4.0 and linked compressibleInterFoam (compressible two-phased flow) with fsiFoam (strongly coupled fluid structure interaction). The fluid side seems to work fine when comparing the results to the original compressibleInterFoam solver. However when i actually implement a solid structure which gets deformed it seems that the deformation is way bigger than it should be. I checked the source code on how the traction/stress on the solid is calculated:

In the tractionBoundaryGradient.C file it says on line 120:

traction = 2*mu*(n & symm(gradField)) + lambda*tr(gradField)*n;

The total traction (stress?) is afterwards updated to (line 463):

Traction = (traction - n*pressure);

As the traction has the unit [kg/m*s^2] the pressure must have the same unit. To me this doesnt make sense as fsiFoam is originally coupled with only incompressible fluid solvers where the pressure is defined as p/rho hence the units are [m^2/s^2]. Should the stress not be calculated like
Traction = (traction - n*pressure*rho) for incompressibel cases? Am i missing something? I assumed that i had to divide the pressure for compressibleInterFluid with the density at some point for the stress/deformation calculation.

Second i was wondering if there is any built in feature i am missing to say that for a certain initial pressure (like 1bar) the stress -> deformation is zero?

I would really appreciate some help/insights on this problems.

Best regards

fuxpaul is offline   Reply With Quote


foam extend 4.0, fsi compressible solver, stress calculation

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Dynamic mesh adaption in parallel calculation xh110120 FLUENT 1 March 12, 2016 08:05
Determining the calculation sequence of the regions in multe regions calculation peterhess OpenFOAM Running, Solving & CFD 4 March 9, 2016 03:07
Traction Force Calculation nabber Main CFD Forum 0 September 27, 2013 05:30
MRF and Heat transfer calculation Susan YU FLUENT 0 June 2, 2010 08:46
Warning 097- AB Siemens 6 November 15, 2004 04:41

All times are GMT -4. The time now is 10:23.