Ansys Employee

The DPM-DEM option also doesn't include a particle volume, it's only collisions that are worked out. It's an option in the DPM model panel, look in the Physical Models tab.

DDPM isn't DEM and uses the Eulerian model when the volume fraction gets higher. It'll also tend to be a transient calculation as the volume fraction tends to alter over the solution duration as waves/dunes of particles form and are broken up. 

With DPM there is a concentration option that may be sufficient - read the definition as it's NOT a volume fraction.