Quoting from CFX-11 Modelling Guide: <blockquote style="padding-top:1em; font-family: courier"> "... In such problems (Gas-Solid Flow), you should assign the solid phase a small insignificant molecular viscosity. This is permissible, as the physics are dominated by inter-phase drag and turbulence effects. ..." </blockquote>
I was wondering what is the reason behind assigning a "small insignificant molecular viscosity"? I would think that a more viscous "fluid" would represent more a solid than one that is less viscous.
Any thoughts?...

This viscosity represents the diffusion of momentum across the solid phase (i.e. the diffusion of momentum from high velocity particles to low velocity particles, as though they were molecules in a fluid). Since the solid velocity is mostly determined by drag forces, this viscosity has little effect on the solution but may affect numerics and convergence.

-CycLone

hi there: found your discussion and wanna ask a q. what if using solid phase with a liquid carrier is it still needs to assign a viscosity for the solid. thanks,