Solid particles in a rotating vessel with 5.7.1

Sandeep

Dear all,

My problem involves studying the motion of solid particles inside an enclosed rotating vessel completely filled with water. The vessel is a cylinder, and has a large diameter to thickness, so I'm modelling it as 2D, with a symmetry boundary condition at both planar faces, and a mesh that's one element thick. I'm using the Lagrangian Particle Transport model in 5.7.1

Before i try to study the effect of vessel rotation, i just want to study the motion of a single particle that could be denser or less dense than water, in a vessel that's stationary. I've specified a user defined drag coeff. using a particle user routine, and the specific particle position within the domian using another particle user routine, but have some problems. The model is one-way coupled.

1. When the particle is injected into the domain with an initial velocity of 0m/s, the particle does not move at all. Shouldn't the particle sink to the bottom of the vessel, as its denser than the surrounding fluid??? When I've given the particle initial velocities of 0.1 & 14mm/s the particle does move, but not at 0 vel. I have had this problem with the user defined drag coeff, and with the default Schiller-Naumann drag coeff selected from the GUI, and with various particle densities. Also in the out file it says Integration Error under Particle Fates - why?

2. When the particle is given an initial velocity, i find that when i select the Schiller-Naumann drag coeff from the GUI, the particle accelerates for a very short period of time, and then reaches a constant velocity - which is what i expect to happen. But when i select the Schiller-Naumann drag coefficient via a particle user routine, the particle does not reach a constant velocity, but keeps on accelerating. This also happens when i select other user defined drag coeffs.

Does anyone have any suggestions?

Thanks

Sandeep