how CFD coupling work, if a loop was defined in liggghts input???

Submitted by tala on Thu, 02/23/2017 - 10:33

Dear all

Hi
I have developed a program in LIGGGHTS to model Triaxial test in soil, it is working well, now i want to couple it with a CFD program to model a saturated triaxial test,
in LIGGGHTS input file I have defined some variables to calculate stresses on stl walls, and a loop to delete and replace the value of variables after moving stl walls after each run.
and the problem is that when I run the coupled program, it starts to run LIGGGHTS first, and enters to the defined loop in it.
After running 100 steps in log file writes:
CFD Coupling established at step 100 (for example)
but, as I saw in "log_run_parallel_cfdemSolverPiso_undrained_CFDDEM" file, CFD related parameteres such "p" and "u" aren't written.

does it working wrong?
:(
any help is appreciated.

Talat,

Forums:

j-kerbl's picture

j-kerbl | Wed, 03/08/2017 - 16:13

Hi Talat,

a LIGGGHTS input script for a coupled CFDEM run typically contains only one run command to initialize the calculation. After that the cfdemSolver "controls" LIGGGHTS and feeds it with forces, etc. and commands to execute. The most important is obviously the run command. The "CFD coupling established" message comes from the fix couple/cfd commands, which set up the exchange arrays for communication.

You definitely cannot use such a loop in a coupled simulation. You can use different input scripts. The you can also use the liggghtsCommands to feed LIGGGHTS with any command during a coupled simulation. E.g. you could set variables from there, unfix movement, ... I guess you could also trigger a "next variable" to run your loops from there.
Have a look at the liggghtsCommands from the tutorials to some examples.

Cheers,
Josef