This is not a pause, it just takes longer to go through the DEM loop than it takes for the Fluid loop:
Here it takes about 3.5 seconds for the DEM loop. There is no intermediate message printed while looping in DEM loop. It will take longer as more particles are injected in the cyclone. You can try with fewer threads and see if you really get a benefit from running in SMP, or if the overhead is too costly for this problem size.
The time step in the run pane controls the fluid time step. The solids time step (DEM) depends on the particle properties and is computed internally. It is displayed at the beginning of the run:
At time = 0.000000E+00 sec., setting DEM solids time step, DTSOLID (sec) = 0.179818E-04```
you can also view it in the message popup: click on the blue text showing the number of messages
This will open a pop-up. Then you can navigate to see the messages: