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It is quite a long time since I ran those simulations. You can try to use the keyword start value in the insert fix (www.cfdem.com/media/DEM/docu/fix_insert_stream.html) if you want no particles for the first part of the simulation.

As far as I remember, Full-JKR was non implemented in LIGGGHTS but only the simplified version you mentioned. I had to implent it in order to take into account all the overlap range of the model. I remember I started from the capillary force model in order to understand how to deal with the pull-off part of the model.

Hi 巫文聪 ! Actually, you will be surprised to know that I don't have any back and front surfaces... but particles don't stay in place by divine force XD. Usually rotating drums are too big to be simulated by our (my) means therefore you just simulate one slice of drum with periodic boundary conditions on the front and back. By the way, you have two easy options to do what you need: 1) subdividing the stl geometry in 2 (cylinder bases and side cylindrical surface) and make all the geometry rotate, in such a way that you can separately hide the unwanted part ( if you have the simulation already done, you can separately simulate the side moving wall without particles, or 1 particle if you find problems); 2)by paraview, apply a clip filter on the moving stl vtk; select box type and check insideout; reduce the scale along the cyclinder axis and center the origin of the box at middle height of the cylinder. It should be fine.

@@tonialessi8694 Thank you so much for your suggestions! I've successfully separated the drum into 2 parts and hided the front and back surfaces~

@@tonialessi8694 Hey, I'd like to ask you one more question. In my simulation, I also defined two sizes of particles like you and use the fix drum to restore the data. (dump dmp all custom/vtk ...) But I can't show the size different in paraview. I can only use Point Gaussian in paraview 5.6 make all particles in sphere with a uniform size. (I only have one vtk file) So do I need to save particle data in in.file with another way (two particles respectively?) or set some filter in paraview? Thanks in advance~

@@user-ln3rn6of4j HI, nice to help you if I can. Sorry for the late answer! Actually you can just: 1) apply on your particle vtk the glyph filter; then within the glyph filter properties: 2)choose sphere glyph type; 3)choose radius scale array; 4)adjust the scale factor (usually 2), just try with 1 or 2 in order to match the bigger particles (showed as point gaussian); 5)select all points glyph mode; 6)apply the changes; 6 and a half)done!

@@tonialessi8694 thanks for your help, it's very kind of you~ I sparated particles into two groups in the in.file and then successfully performed the simulation. But I'll also try your guidances

PISO solver for incompressible fluids

Thank you for the response. There are 4 piso solvers for incompressible fluids in the CFDEM project. Did you use cfdemSolverPiso solver?

@@honorhonor5352 , exactly!

@@tonialessi8694 Thank you. Please can you share your setup with me via honordoubled@gmail.com? Thank you

Introducing heterogeneous catalytic reactions is one of the most recent challenges in CFD-DEM. Unfortunately this simulation is only to evaluate the flow pattern. With OpenFOAM, you can actually introduce the moving mesh, independent on the DEM mesh, which is only used to find contacts. I never did a CFD-DEM simulation with a fluid moving mesh, I am sure that is actually feasible, at least with a 1 way coupling. In some cases, i.e. a rotating drum without baffles, you can make the drum rotate, solid side, and implement a BC on the fluid to implement the wall shear.

Sure! You can start from one tutorial and adjust it as you need. In the input file, you have to introduce the stl fix and move/mesh fix, in order to insert the drum stl and make it rotate. I defined the fixes for two particle templates (different properties) in order to be able to generate the two species separately in different generation regions. It is quite easy... the timestep should be fixed by following a criterion, for instance 20% of Rayleigh time-step or 1/15 of the collision time at the maximum expected velocity, considering the smallest particles.

Thanks a lot, I´m going to try with your recomendation, and see what happend.

We have uploaded a few tutorial for LIGGGHTS. If you like you can have a look if they are helpful for your application. Nice simulation by the way