can you have variable density for solid dispersed?

Tim

Hi,

I am trying to run a 2 phase simulation with air and 2mm solid dispersed particles. In this simulation I am trying to make the density of the solid dispersed phase to be variable i.e. decreases as the y coordinate decreases. I created a new material and in the density I used a formula. The units are correct, however I get this message

Fatal bounds error detected --------------------------- Variable: Particles.Density Locale : Default Domain

Is it possible to do what I am trying to do?

Also with a Eulerian-Eulerian simulation is there any method of imposing a friction coefficient between the solid dispersed phase and a wall? Or can it only be no slip or free slip?

Thanks, Tim.