I am using particle tracking to evaluate flow and mixing. It is a transient problem (sliding mesh) and I note that the number of particles decreases with time. I tried to decrease the time step, but it does not help. The boundary conditions of the DPM on the walls are set to preserve the momentum of the particles. It has probably to do with the moving mesh and the wall (velocity relative to adjacent cells set to zero) conditions? I wonder if this is a bug in the program fluent or is there anything I could try? Thanks Lucy.

Hi,

Assuming you're using a 'reflect' condition on all wall surfaces - what does the fluent console report during the dpm iteration? It should specify the total number of particles tracked and their respective fates - ie trapped, escaped, incomplete etc. This will give you a clue as to where your particles are going.

Regards

Steve

The boundary conditions are correct in my model. The particles disappear when the moving wall sweeps the particles. Using a much smaller time step would be better...but this is something that I would like to avoid... I think there is no help in this case. Lucy.

Hi,

Fluent moves particles already in the domain as the grid moves to prevent domain walls moving over particles and losing track of them. It doesnt move surface injections though so if a wall moves over a surface injection you'll get a warning during the simulation like 'can't find starting cell for * new particle' and lose particles that way. Also if you have an individual wall moving but the grid remaining stationary (deforming grid) you may have a wall step over a particle and hence lose track of it. Sounds like this is happening in your simulation - I've used DPM on a case with two sliding fluid zones and didnt have any problems. Any chance you can use rotating reference frames instead?

Steve

[Pong]

Hi, Steve
when I use DPM on a case with sliding fluid zone,there's a problem: Warning: unexpected BC at sliding boundary.How to deal with it? Thanks