Shear stress applied to mesh cells in vector form

Submitted by Dam_Nik on Sun, 05/15/2022 - 18:08

Hello everyone!

I'm working on a simulation and I could really use some help. I want to simulate the flow of granular material in the space between two concentric cylinders. The inner cylinder is rotating and therefore causes the material to move. It's something like a rheometer but with granules instead of fluid.

I'm measuring the velocity of the particles and the stress (normal and shear) that is applied in the meshes of the two cylinders. Ultimately I want to get these stresses with respect to the height of each one of the meshes. Normal stress is not a problem, but shear stress is where I struggle.

I use the following commands to measure and print the stresses:

fix In_wall_s all mesh/surface/stress file meshes/Small/In_wall_s.stl type 2
fix Out_wall_s all mesh/surface/stress file meshes/Small/Out_wall_s.stl type 2

dump d_a_2 all mesh/gran/VTK ${dump_rate_3} post/In_wall_s_*.vtk stress In_wall_s
dump d_a_3 all mesh/gran/VTK ${dump_rate_3} post/Out_wall_s_*.vtk stress Out_wall_s

where In_wall_s is the mesh of the inner and Out_wall_s is the mesh of the outer cylinder. This way I can dump, every certain timestep, the normal stress and the shear stress that is applied to every cell of the meshes from the particles independently. However, these values are printed as scalars for every cell of the mesh.

What I want is to get the shear stress in the form of a vector, so I can eliminate the contribution in the z-direction and have the shear stress parallel to the XY plane.

Does anyone know how to do that? Is there any other way to get the aforementioned desired results? Any help would be highly appreciated!
Thanks in advance!

Damianos