im using 3D cylindrical bed to predict Umf but the umf predicted in 3D cylinder is almost 2 times than predicted from 2D geometry bed. why this is happening even all the parameters and values keep same in both cases ? i attached here .mfx file and .stl file . im using cut-cell method in this. please help
geometry.stl (983.0 KB)
Umf_BRNS_3DCylinder.mfx (10.7 KB)
How are you predicting the Umf? You have a constant inlet velocity here. I didn’t run your case, but there are issues with the geometry/boundary conditions. You have added bottom and top caps to the cylinder. They interfere with the other inlet and outlet BCs. The top cap is located at y=0.3m while ymax=0.301m (slightly higher). This mean there is a wall at y=0.3m and an outlet at y=0.301m, but the outlet is inactive since it falls outside the fluid domain (due to the wall at y=0.3m ). It is best to extend your cylinder past the y=ymin and y=ymax planes (increase the cylinder’s height and translate it down in the y-direction) so they do not interfere with the inlet and outlet BCs.
Thank you ! at Outlet BC i want bed to be open at atmosphere pressure so should i need to remove cap from top outlet region and also need to remove cap from bottom ? and giving only constant bottom inlet at 0.3 m/sec. the height 0.301 is increased from 0.30 due to autosize setting in mfix. if possible please check this with run so we can know what are other issues with this to understand the exact cause of wrong Umf prediction.
My suggestion was to extend the height of the cylinder so it sticks out of the MFiX box. Then it doesn’t matter if there are caps because they will be out of the domain and thus ignored. You can keep ymin=0 and ymax=0.3, and set for example the cylinder’s height to 0.32m an translate it down by 0.01m so its y-extent is [-0.01;0.31]. You can try with and without the caps and you will see you get the same mesh. You should always inspect the mesh before running the simulation. I like to look at the boundary mesh in the GUI as it helps identify obvious issues with the mesh.
yes i tried without caps its creating issue but after fixing height and with caps and meshing , the problem resolved for scaled down bed. thank you !