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Viscosity for solid in Gas-Solid Two-phase Flow

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Old   January 23, 2008, 12:00
Default Viscosity for solid in Gas-Solid Two-phase Flow
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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?...
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Old   January 23, 2008, 18:32
Default Re: Viscosity for solid in Gas-Solid Two-phase Flo
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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.

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Old   January 30, 2008, 01:44
Default Re: Viscosity for solid in Gas-Solid Two-phase Flo
shehab abdelrahman
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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,
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