Laminar Flow and Particle Track: Inconsistent?
 

Hi guys,

I am running a very simple laminar case in a straight annular pipe, and I did generate a solution using velocity inlet boundary condition and a pressure outlet b.c.

I double checked the velocity profile which match very well the analytical solution available in textbooks, but, surprisingly, when I tried to inject particles at the inlet...well...such particles don't quite follow the velocity streamline. It seems they cluster annular regions of the reactor. And I don't have particle closed to the external wall.

FYI, I defined particle with the same density of the water and I did not include any gravity effect. So, I can't undestand particles shouldn't follow streamlines...

Any thoughts?